Letter XXXV

Letter XXXV

EXTERNAL ANATOMY OF INSECTS, CONTINUED.

THE TRUNK, AND ITS PARTS AND ORGANS.

As the head of insects is the principal seat of the organs of sensation, so is the trunk of those of motion; and in it are contained the muscles by which they are moved: it may therefore be regarded as the great centre of motion, and as the main support and prop of the two other primary sections of the body--the head and abdomen, between which it is situated--it may be deemed the most important part of the insect, the key-stone of the whole structure. In treating upon it, for the greater clearness, I shall consider its substance, general form, proportions, composition, internal processes, and members. It will first, however, be necessary to assign my reasons for the nomenclature of its parts that I have adopted.

Had the entomological world been universally agreed upon this subject, and there was an established system of Orismology[1585], I should have proposed no alteration without great reluctance, and the fullest conviction of the absolute necessity of some change; but as the standard of language in our science is still unsettled, and different terms are used by different writers, there seems full liberty left to me to select those that appear upon the whole most appropriate; and where proper and significant terms seem wanting, to invent new ones. M. Latreille, in a late Essay[1586], has proposed many changes of this kind, and seems to hesitate concerning the adoption of some of those recently coined in France for the parts of the trunk[1587]; it may therefore, I think, be permitted me to labour a little in this hitherto imperfectly cultured field, and to suggest such improvements as the subject may seem to require or admit.

Linné called the part we are now considering the trunk, its upper-side he usually denominated the thorax, and its under-side the breast: he notices also the scutellum and sternum[1588]. As the prothorax and scutellum are the only apparent parts of the back of the trunk in his first Orders (Coleoptera, Hemiptera L.), the rest being covered, in noticing these he puts the part for the whole, calling the prothorax the thorax, but which strictly was not synonymous with what he called by the same name in the other Orders. Linné's phraseology with regard to the trunk of insects was adopted by Fabricius and other Entomologists, till Illiger employed the term thorax to designate the whole of the trunk[1589], calling the upper part thorax superior and the lower thorax inferior. M. De Blainville, M. Latreille, and other French writers, improved upon this, naming the upper part the back (dorsum), and the lower the breast (pectus); and dividing the trunk, or according to them thorax, into three sections, each bearing a pair of legs. But I see no sufficient reason for this alteration--the terms trunk, thorax, and breast, in the common acceptation are well understood, and lead to no confusion or glaring impropriety; I shall therefore adhere to the old phraseology, especially as French Entomologists in popular language still do the same.

As to the division of the trunk into segments by M. Latreille and others, it has been regarded as consisting of three primary ones, which have been called in the order of their occurrence, reckoning from the head--prothorax, mesothorax, metathorax. The first of these segments, however--and the learned Entomologist just named seems to hint as much[1590]--is usually more distinct from the other two, than they are from each other. If this idea be correct, the trunk is properly resolvable into two primary segments, the first bearing the arms or fore-legs, and the other the proper legs and the organs of flight. M. Chabrier calls the latter tronc alifère, or wing-trunk;--a happy term, which I have adopted and latinized, calling it the alitrunk (alitruncus): the first segment, because it bears the fore-legs, I have named manitrunk (manitruncus). I adopt likewise the terms above mentioned, prothorax, mesothorax, metathorax, to signify the three segments into which the thorax of Linné, or the upper side of the trunk, is resolvable; and those of the breast I denominate antepectus, medipectus, and postpectus. If terms be thought necessary to designate the two intire segments into which the alitrunk is resolvable, the first may be the meditrunk (meditruncus), and the other the potrunk (potruncus).

I. Substance.--With regard to its substance, the trunk in general is softer than the head, and harder than the abdomen, especially as to its upper surface; but in some cases, where it is not protected by the elytra, as in the rove-beetles (Staphylinus L.), the abdomen appears as hard as the trunk. Though usually not very different from the elytra in this respect, in Meloe, Lytta, and other vesicatory beetles, it is of a firmer consistence.

II. General Form.--In the Coleoptera Order the only part of the trunk that is visible on its upper-side is the prothorax: the mesothorax, with the exception of the scutellum, and the metathorax, being entirely concealed by it and the elytra; so that, with regard to shape, it may nearly be considered as merging in the prothorax. Below it is more visible, and may be stated as more or less quadrangular; in oblong beetles inclining to a parallelogram, and in shorter or hemispherical ones to a square. In the majority it is more convex below than above, except in the case of the hemispherical or gibbous beetles (Coccinella, Erotylus, &c.), in which the under-side is flat and the upper-side very convex. In the Diurnal Lepidoptera the trunk approaches to a cubical shape, in the Nocturnal it is more spherical. A similar difference obtains in the Hymenoptera and Diptera: in the bees, wasps and flies, the trunk approaching to the figure of a sphere; in the ants, Scoliæ, crane-flies, &c. to that of a cube. The upper part of it in many Ichneumonidæ, female ants, &c. is very elevated, forming an arch, and sloping towards the abdomen. In general it may be observed with respect to the remaining Orders, that the form of the trunk merges in that of the whole body, the tendency of which is often to a three-sided figure.

III. Proportions.--The trunk is usually longer and larger than the head and longer than the abdomen, but not wider: but there are exceptions to both these rules. In Colliuris, Mantis, &c., it is more slender; and in Atta megacephala and some neuter ants, it is shorter than the head; in Atractocerus, many Staphylinidæ, Phasma, the Libellulina, the Lepidoptera, and various Hymenoptera, it is shorter, and in the Mantidæ more slender than the abdomen. The greatest disproportion between it and the last part is exhibited by the genus Evania, parasitic upon the Blattæ, in which the abdomen appears merely as a minute and insignificant appendage of the trunk. The vertical diameter of this part, almost without exception, is greater than that of either head or abdomen. When we consider that it contains the muscles that move both the organs of flight and the legs, we see clearly the reason why the CREATOR gave it greater volume.

IV. Composition.--I lately intimated to you that the trunk, though resolvable into three segments, in most cases properly consists of only two primary ones. Whoever examines the perfect insects of every Order, except the Aptera[1591], will find this distinction strongly pointed out, not only by the different direction of the first pair of legs from that of the two last, but also in a large proportion by a deep incisure; and in all it is further manifested by the anterior segment having a motion distinct from that of the rest of the trunk, and separating readily from it; and this not only where it is large, as in insects that have a thoracic shield, but also in those in which the prothorax is less apparent: whereas the other two pedigerous segments have little or no distinct motion, will not readily separate from each other, and in some cases exhibit no pectoral suture between them. Sometimes, however, these two last segments are more prominently distinguished: in Lytta, Mylabris, and other vesicatory beetles, they are separated below by an incisure, or rather the first or mid-leg segment, is not nearly so elevated as that of the hind-legs. In some ants (Atta Latr.), in the neuters, there is no distinction of segments in the trunk; but in others (Formica Latr.) it follows the general law, and consists of three. In the Arachnida, with the exception of Galeodes, in which the head is distinct, and the three segments of the trunk may be traced, these parts together form only a single segment. Induced by these reasons, I consider the trunk as consisting in general of two primary segments, the manitrunk and alitrunk: the latter resolvable into two secondary ones.

* Manitruncus[1592].--The manitrunk, then, is the anterior section of the trunk, which bears the arms and contains the muscles that move them. This part has free motion, or a motion independent of that of the rest of the trunk. This indeed seems a necessary result of the direction and uses of the arms. It consists of an upper and lower part--the prothorax and antepectus.

i. Prothorax[1593].--The upper part of the manitrunk in the Coleoptera, Orthoptera, and Hemiptera, is by far the most conspicuous part of the trunk, but in the other Orders it is less so. With respect to it, insects may be divided into two classes--those that have and those that have not a prothorax. In the Coleoptera Order it is remarkable both for size and variations in its shape and sculpture. In the Orthoptera, though less various, it is almost equally conspicuous, especially in Blatta. In the Homopterous section of the Hemiptera, in many genera it has become extremely short; while in the Heteropterous section its dimensions are not much reduced. In the majority of the Neuroptera, likewise, it is comparatively large; in the Libellulina much shorter, and in the Trichoptera and Lepidoptera nearly evanescent[1594].--In the Hymenoptera and Diptera, with very few exceptions, the thoracic shield altogether disappears, at least if I am correct in an idea, which I shall hereafter explain, that the collar usually regarded as the analogue of the prothorax, is really a part of the alitrunk. In these last Orders, though there is no true prothorax, the manitrunk still remains under the form of an antepectus, bearing the fore-legs, and containing the muscles that move them.

The prothorax of insects may in general be considered with respect to its parts, margin, appendages, shape, sculpture, clothing, and proportions.

1. The prothorax, regarded as a whole, distinct from the antepectus or fore-breast, consists commonly of two pieces--the shield, or upper part[1595], and the ora, or under part[1596]. In the shield you are to observe its apex[1597], base[1598], sides[1599], limb[1600], and disk[1601]. The apex is the part next the head; the base that next the abdomen; the limb the circumference, and the disk the central part. In many Orthoptera and Heteropterous Hemiptera, the shield appears further to consist of two pieces, an anterior and posterior one. The ora is a continuation of the shield below the lateral margin, turned downwards and inwards towards the fore-breast and the legs, but separated from the former in most cases by a suture, as in Carabus L.; and in others merely by an impressed line, as in Blaps F.; but in Curculio and Cerambyx L., &c. there is no ora, the shield being without a lateral margin, and forming one piece with the antepectus. The part we are now considering varies in different genera. Sometimes it is very narrow, as in Scarites; at others very broad, as in Buprestis, Nepa, &c. In Lampyris, except L. italica, and affinities, it projects posteriorly into a lobe or tooth, which forms a right angle with the rest of the ora, and becomes the lower part of the cavity that receives the head; and in Dermestes this part is excavated into an anterior and posterior one which admits the antennæ and arms when folded for repose.

2. The margin of the prothorax is a ridge, either defining its sides or whole circumference. In many cases this margin is broad and dilated, but in others it is merely a thread or bead that separates the shield from the ora. Though generally terminating the upper surface, it sometimes, as in Staphylinus, dips below it. In many insects, however, as I just observed, the thoracic shield has no lateral margin whatever.

3. Various and singular are the appendages with which the prothorax of numerous insects is furnished. Many of these are sexual distinctions, and have been before described to you[1602]; but there are others common to both sexes, the most remarkable of which I shall notice.--Some are distinguished by a long horn which overhangs the head, as Membracis cultrata, ensata, &c.[1603]; in others it stands upright, as in Centrotus spinosus[1604]; C. Taurus has a pair of thoracic horns like those of a bull, only dorsal[1605]; in Ledra aurita they are flat, and represent ears[1606]; in some species of Tingis (T. Echii, Pyri, &c.) a kind of reticulated hood, resembling lace, is elevated from the anterior part of the prothorax, which receives and shelters the head[1607]. In Centrotus globularis and clavatus F., especially the former, the part in question is armed by a most singular and wonderful apparatus of balls and spines,--in one case standing erect[1608], and in the other being horizontal[1609],--which gives these animals a most extraordinary appearance. In many of the species here quoted the prothorax is producted posteriorly into a long scutelliform horizontal horn, which more or less covers the wings and abdomen; a circumstance which also distinguishes the genus Acrydium F. (Tetrix Latr.). This horn seems to have been sometimes regarded by Linné and Fabricius as a real scutellum, and sometimes only as a process of the prothorax: but that it is merely the latter will be evident to you, if you examine carefully any insect furnished with this appendage; for if you remove that part, you will discover the true scutellum and other parts of the trunk concealed beneath it. A very remarkable prothoracic appendage is exhibited by some species of Mantis. In general the part we are treating of in this tribe is very slender; but in M. strumaria, gongyloides, &c., it appears dilated to a vast width, and assumes, either partially or generally, a subrhomboidal form; but if it is more closely examined, it will be found that the form of the prothorax is really similar to that of the rest of the tribe, but that this part is furnished on each side, either on its whole length or anteriorly, with a large membranous flat subtriangular appendage resembling parchment[1610]. Perhaps this kind of sail may be useful to the animal in flight. In Prionus coriarius &c. its sides are armed with teeth, and in many Lamiæ, Cerambyces, and other Capricorn beetles, and often in various bugs (Pentatoma Latr.) with sharp fixed spines. But the prothorax has moveable as well as fixed appendages; of this kind are those spines (umbones), whose base is a spherical boss moving in an acetabulum of the thoracic shield of the Capricorn subgenus Macropus Thunb. If I might hazard a conjecture, I should say that these organs were given to this animal by an all-provident CREATOR, to enable it to push itself forward, when in the heart of some tree it emerges from the pupa, that it may escape from its confinement. Another kind of moveable appendages are attached to the thorax of Lepidoptera, usually in the form of a pair of concavo-convex scales covered externally with a tuft of hairs[1611]. M. Chabrier, who examined these scales in recent insects, describes them as vesicles, which appeared to him full of a liquid and of air, and capable of being alternately inflated and rendered flaccid; he regards them as accessories to a pair of spiracles, which he looks upon as vocal[1612], opening into the manitrunk just above the insertion of the arms. These organs are quite distinct from the tegulæ that cover the base of the primary wings of insects of this Order[1613], and are what, borrowing a term from Mouffet[1614], I have called in the table patagia, or tippets. Under this head I may include the caruncles at the anterior angles of the prothorax of a genus of beetles with soft elytra, named by Fabricius Malachius. When pressed, says De Geer of these insects, a red inflated soft vesicle, of an irregular shape, and consisting of three lobes, emerges from the thorax and from each side of the anterior part of the abdomen, which re-enters the body when the pressure is removed[1615]. M. Latreille seems to think that these vesicles have some analogy with the poisers of Diptera and the pectens of scorpions; and that they are connected with the respiration[1616].

4. We are next to say something upon the shape of the prothorax. The forms of the thoracic shield, especially in the Coleoptera, are so various, that it would be endless to aim at particularizing all; but it may be useful to notice a few of the most remarkable. The prothorax of Moluris, a darkling-beetle, approaches the nearest of that of any insect to a spherical form, from its remarkable convexity; in the wheel-bug (Reduvius serratus) it is compressed, and longitudinally elevated into a semicircular serrated crest: it is crested, also, in many Locustæ and Acridæ, in some having two parallel ridges; but, generally speaking, its surface is more depressed. In Necrodes it is nearly circular, in Blatta petiveriana semicircular, in Nilion and some Coccinellidæ crescent-shaped, in Carabus obcordate, in Cantharis and Sagra approaching to a square, in Languria to a parallelogram; in many Cimicidæ, Belostoma, &c., it is triangular, with the vertex truncated; it is trapezoidal in Elater, in Ateuchus rather pentagonal, and exhibiting an approach to six angles in some other beetles[1617]: but the prothorax most singular in form is that of some species of M. Latreille's genus Helæus[1618], as H. perforatus, Brownii, &c.: in these its anterior angles are producted, and curving inwards, lap at the end one over the other, so as to form a circular orifice for the head, which otherwise would be quite covered by the shield. Thus the upper portion of the eyes can see objects above, as well as their lower portion those below. I might enumerate many other forms, but these are sufficient to give you some notion of the variations of this part.

5. The prothorax is equally various in its sculpture; but since in the Orismological table almost every instance of it has its place, I shall here only notice it as far as it is common to the whole tribes, genera, or subgenera. The Scarabæidæ of Mr. W. S. MacLeay are distinguished by a small excavation on each side of this part, which, as has been before remarked[1619], furnishes an elevated base for an internal process with which the anterior coxæ ginglymate. In Onitis and Phanæus, to these excavations are superadded a pair impressed in the base of the prothorax, just above the scutellum; in Carabus L. a longitudinal channel divides the thoracic shield into two equal portions; and many genera of that great tribe have in addition, at the base on each side, one or two excavations or short furrows. Elophorus F. has on this part several longitudinal channels, alternately straight and undulated. Generally speaking, in Carabus L. the prothorax has no impressed points; but in one or two subgenera of Harpalidæ (Chlænia &c.) it is thickly covered with them. In numbers of Locusta Leach, the part we are considering is what Linné terms cruciate, being divided into four longitudinal portions by three elevated lines, the intermediate one being straight, and the lateral ones diverging from it both at their base and apex, so as to form a sinus or angle[1620]. In certain Acridæ K. (Locusta F.) there are only two of these lines or ridges, but notched or toothed; and in some of the genus first named only one[1621]; in Locusta Dux and affinities the prothorax has several transverse channels or rather folds[1622], with corresponding ridges on its internal surface.

6. With respect to the clothing of the prothorax, I have not much to say: in Coleopterous insects this part is commonly naked; but in some genera, as Byrrhus, Anthrenus, Dermestes, and many weevils (Curculio L.) it is partially or totally covered with hairs or scales. In the other thoracic Orders it is usually naked, but in some Neuroptera, the Myrmeleonina, &c., it is hairy; and in the Libellulina it is fringed posteriorly with hairs.

7. As to its relative proportions, the prothorax is sometimes rather wider than the rest of the trunk and the head, as in Onitis, Pasimachus, &c.; it is considerably narrower in Collyuris and Odacantha; and of the same width in those Scaritidæ with striated elytra[1623]. Again, it is sometimes of the same width with the elytra, but wider than the head, as in Hydrophilus, Dytiscus, &c.; in some instances it is of the same width with the head, and narrower than the elytra, for instance in Anthia and Brachinus. In most Coleoptera it is longer than the head and shorter than the elytra; but in Manticora, the vesicatory beetles, &c., it is shorter than either. In Gnoma longicollis[1624], it is nearly as long as the elytra; in many Staphylinidæ, Atractocerus, &c., longer; in Phanæus carnifex, bellicosus, &c., it is longer than the elytra and the rest of the body. With regard to itself, it is sometimes very wide in proportion to its length--Dytiscus, Helæus; at others very long in proportion to its width--Colliuris, Brentus, Mantis, &c. In Flata, and many other Homopterous Hemiptera, it is extremely short; extremely long in Gnoma; in Sagra and Donacia its width about equals its length; in Elater, Dytiscus, and many Heteropterous Hemiptera, it is narrowest before; in Languria it is every where of equal width; in Anthia, Carabus, &c., it is widest before; and, lastly, in the Scarabæidæ MacLeay it is usually widest in the middle.

ii. Antepectus[1625].--The antepectus, as was before observed[1626], in some tribes forms one piece, without any kind of separation, with the prothorax; but very often this is not the case. In Carabus L. it occupies almost the whole under-side of the manitrunk; but in Elater, in which the ora is very wide, the antepectus is merely the middle portion of that part. In Carabus F. &c. between the ora and the base of the arms is a convex triangular piece, distinguished from the rest of the antepectus by a spurious suture; and in Pentatoma and other Heteropterous Hemiptera a similar piece is observable, which terminates in a convex bilobed subtriangular sheath, receiving the base of the clavicle[1627]. This piece seems a prop to that part, and analogous to the scapula of the medipectus and parapleura of the postpectus. I shall say no more upon the antepectus, as it is seldom remarkable. In the mole-cricket, however, one peculiarity distinguishes it: it is in this of an elastic leathery substance, while the prosternum is hard, resembling a bone. In other instances these parts are both of the same substance.

1. The sternum or breast-bone of insects consists mostly of three distinct pieces; in this resembling the human sternum, which is described by anatomists as composed originally of three bones[1628]. Each of these pieces is appropriated to a pair of legs, and each of them at times has been called the sternum: thus in Elater the prosternum, in the Cetoniadæ the mesosternum, and in Hydrophilus the metasternum, have been distinguished by this name. Our business is now with the first of these pieces, the sternum of the antepectus or prosternum[1629]: this is the middle longitudinal ridge of the fore-breast, which passes between the arms, when elevated, extended, or otherwise remarkable. It is most important in the Coleoptera Order, to which my remarks upon it will be chiefly confined. In these it is sometimes an elevation, and sometimes a horizontal process of the fore-breast. If you examine the great Hydrophilus (H. piceus), at first you will think that there is only a single sternum common to all the legs; but if you look more closely, you will perceive between the head and the arms a triangular vertical process, with a longitudinal cavity on its posterior face, which receives the point of the mesosternum that passes between the arms[1630]: this vertical piece is the real prosternum, and not the other, which really belongs to the alitrunk. In this case the elevation of the prosternum is before the arms; in others it is between them, as you may see in a Chinese chafer (Mimela K.), which imitates the external appearance of a quite different tribe[1631]; in others again it is behind them, as in most of the Lamellicorn beetles. In the common dung-chafer (Geotrupes stercorarius), it is a hairy process, which, when the head is bent downwards, is received by a deep cavity of the mesosternum. The Dynastidæ MacLeay may always be known by a columnar prosternum rising vertically between the arms and the medipectus. Lastly, in other tribes there is a prosternal elevation both before and behind the arms, as in Cerambyx thoracicus, dimidiatus, and affinities. Of the second description, those that have a less elevated horizontal prosternum, the point in most is to the anus, but in some to the head: thus in Carabus L. it is generally a subspathulate flat piece, the point of which slides over the mesosternum, or covers it; but in Harpalus megacephalus Latr.[1632], one of this tribe, though similarly shaped, its point is to the head. These horizontal prosterna vary in their termination. In that of Carabus L. the apex is obtuse; in that of Elater, above described[1633], and Dytiscus it is acute; in Prionus lineatus, Spencii K., &c., it is bilobed; and in Buprestis variabilis, attenuata, &c., obsoletely trilobed. With regard to the other Orders no striking features of this part are observable, except in some Orthoptera. In Acrida viridissima K. (Locusta F.) it is represented by two long filiform vertical processes; and in Locusta Leach by a single conical horn[1634], mistaken by Lichtenstein for a process of the throat[1635]. In one instance, Gryllotalpa, this part is a long piece between the arms, shaped like the human thighbone or tibia, being more slender in the middle and widest at the ends, and which is of a much harder substance than the rest of the antepectus, and forms the lower termination of a singular machine which will before long be noticed. In many bugs (Cimicidæ), instead of being elevated, the three portions of the sternum are hollowed out into a longitudinal groove, in which the promuscis when unemployed reposes.

The most conspicuous and remarkable appendages of the manitrunk, are the brachia or arms. I shall not, however, enter into the full consideration of these, as they consist numerically of the same parts, till I treat of the legs in general. Here it will only be necessary to assign my reasons for calling them by a distinct denomination. In this I think I am authorized, not only by the example of Linné, who occasionally found it necessary to do this[1636], and more particularly by the ancient notion that this pair of organs in insects were not to be reckoned as legs[1637], but likewise from their different position and functions. They are so inserted in the antepectus as to point towards the head, whereas the other two pair point to the anus. With regard to their functions, besides being ambulatory, and supporting the manitrunk in walking, they are applied to many other purposes independent of that office,--thus they are eminently the scansory or climbing legs in almost all insects; in most Carabi L., by means of the notch and calcar[1638], they are prehensory legs; in Scarites belonging to that tribe, the Lamellicorn beetles, and the mole-cricket, they are fossorious legs, or proper for digging[1639]; in Mantis, Nepa, and some Diptera, they are raptorious, or fitted to seize and dispatch their prey[1640]: they are used also by many insects to clean their head, eyes, and antennæ, &c. For many of these purposes they cannot be fit without a structure different from that of the other legs, which renders it a matter of as great convenience in descriptions to speak of them and their parts under different names from those of the legs, as it is of the arms of man; on this account it is that I propose to give to the fore-leg and its part the names by which the analogous parts, or what are so esteemed, in the human species are distinguished;--when spoken of in common with the other legs, they may still be called the forelegs.

* * * * *

** Alitruncus. The alitrunk is the posterior segment of the trunk, which below bears the four true legs, and above the organs for flight or their representatives. In treating of this part we may consider its insertion or articulation, its shape, composition, substance, motions, and organs.

i. With regard to its insertion, or articulation with the manitrunk and abdomen, it may be observed that it is attached to both by its whole circumference by means of ligament; in the Coleoptera, Orthoptera, and Heteropterous Hemiptera being received by the posterior cavity of the prothorax, the shield of which in these Orders, especially the last, almost covers and conceals it; but in the remaining ones it is merely suspended to it. In the former also, especially in the Coleoptera, it seems more separate and distinct from the manitrunk than from the abdomen, and more independent of its motions than of those of the latter part: but in the Hymenoptera and Diptera its greatest separation is from the abdomen in both respects. In many insects, as in the Lamellicorn beetles, the mole-cricket, &c., the manitrunk terminates posteriorly, drawing a line from the base of the prothorax to the antepectus, in an oblique section; in other tribes, as in the Cerambyx L., the Predaceous beetles, &c., the section here is often vertical, but in the alitrunk the anterior one is always vertical, while the posterior, by which it articulates with the abdomen, in the Orders with an ample thoracic shield, is oblique, so that the pectoral portion is more ample than the dorsal.

ii. As to its composition, the alitrunk is usually much more complex than the manitrunk; for, besides the instruments of motion, it consists of numerous pieces. It may be regarded as formed of two greater segments, the first bearing the elytra, or the primary wings, and the intermediate legs; and the second, the secondary wings and the hind legs.

1. Collare[1641]. The first segment of the alitrunk is the middle piece of the whole trunk, and therefore, when spoken of per se, may be called the meditruncus. It consists primarily of an upper and lower part, which in the table are denominated the mesothorax and the medipectus. The first piece in the former that requires notice is the collar. I formerly regarded this piece, which is peculiar to the Hymenoptera, Diptera, and one tribe of the Neuroptera, as the representative of the prothorax in the other Orders, and this opinion seems at this time very generally adopted, but subsequent observations have caused me to entertain considerable doubts of its correctness. Many other Entomologists have thought it improper to distinguish these parts by the same name[1642]. Much, however, may be said on both sides of this question, and I shall now lay before you the principal arguments that may be adduced in defence of each opinion, beginning with those that seem to prove that the collar is the analogue of the prothorax. First, then, the collar, like the prothorax, is placed precisely over the antepectus, and being placed in the same situation, on that account seems entitled to the same denomination; especially as in some genera, for instance Chlorion F., it assumes the very semblance and magnitude of a thoracic shield, and is separated from the mesothorax by a considerable incisure. Again, in some cases that have fallen under my own observation, the collar is endued with some degree of motion distinct from that of the alitrunk, since in Pompilus and Chrysis the animal can make the former slide over the latter in a small degree. A third and last argument is, that no prophragm is formed from the collar: insects that have a thoracic shield are generally distinguished by having the anterior margin of the dorsolum deflexed so as to form a septum, called in the table the prophragm, which enters the chest and separates the cavity of the mesothorax from that of the prothorax; now in Hymenoptera this septum is a process of the piece behind the collar, and excludes it from having any share in that cavity. These arguments at first sight seem to prove satisfactorily the identity of the collar and prothorax. But audi alteram partem, and I think you will allow that the scale containing the claims of the collar to be considered as a piece sui generis, dips much the lowest. And, first, I must observe, that though in Hymenoptera the collar seems to replace the prothorax by its situation, yet it is in fact a part of the alitrunk; for, if the manitrunk be separated from the latter, the collar remains, in most cases, attached to it[1643], while the antepectus and arm, with the ligament that covers its cavity above, the real representative of the prothorax, are easily removed, and this in recent individuals: as a further proof of this, I must request you will examine a neuter Mutilla; you will see that in this the collar is not separated from the alitrunk in any respect, but forms one piece with it, while the antepectus is distinct and capable of separate motion: further, the action of the collar is upon the alitrunk, it being of essential importance in flight, whereas the prothorax is of no other importance than as a counterpoise to that part[1644]. A further argument to prove the distinction of these parts may be drawn from the case of Xylocopa, a kind of bee. In this genus the collar forms a complete annulus or segment of the body: now, if it really represented the prothorax, the under side of the segment, as in those Coleoptera in which no suture separates the upper from the lower part of the manitrunk[1645], should represent the antepectus, and have the arms inserted in it; but in the case before us there is a distinct antepectus bearing the arms received by the socket formed by this annulus. But the most powerful argument is the fact that some insects have both the prothorax and collar, a circumstance that completely does away every idea of their identity. If you examine the common hornet (Vespa Crabro), or any saw-fly (Tenthredo L.), you will find, as was before intimated, that the real covering of the cavity of the manitrunk is a ligamentous membrane, which properly represents the prothorax. In another genus of the same order (Xiphydria Latr.), the sides of the antepectus turn upwards and nearly form a horny covering distinct from the collar[1646], the ligamentous part being reduced to a very narrow line, and in Fœnus the dorsal fissure is quite filled up, so that in this the manitrunk is perfectly distinct, and exhibits both prothorax and antepectus of the usual substance. In Nomada likewise, N. Goodeniana K. was the species I examined, there is a short minute prothorax besides the collar. Next let us turn our attention to the Diptera; if you examine the common crane-fly (Tipula oleracea), you will find, first, a regular short prothorax, to which the antepectus, with the arms, is attached; and behind this also is a short collar embracing the alitrunk anteriorly. The next insects that I shall mention, as exhibiting both prothorax and collar, are the Libellulina. These are generally admitted to have the former of these parts[1647], but besides this they have also the latter, which is the most ample and conspicuous piece in the whole trunk[1648]; intervening, as the collar should do, between the prothorax and those parts of the trunk to which the wings are attached. There is one circumstance connected with the subject which should not be overlooked. In the Hymenoptera, usually under a lateral process of the posterior part of the collar, is a spiracle or respiratory apparatus; in the Diptera there is also one, though not covered by the part in question, in the same situation; now this you will find precisely so situated with respect to the second piece in the thorax of Tipula oleracea, proving that this piece is the real representative of the collar. Enough, I think, has been said to satisfy you that I have not changed my sentiments on this subject upon slight grounds. Probably traces of the part in question might be detected in the thoracic Orders in general, in connexion with some vocal or respiratory organ[1649]; but having had no opportunity, by an extended examination of living subjects, to verify or disprove this suspicion, I shall merely mention it, and conclude this head by observing, that the collar varies most in the Hymenoptera order, and that its most remarkable form is in Vespa, Cimbex, Dorylus, &c., in which it bends into an ample sinus that receives the dorsolum[1650].

2. Dorsolum[1651]. Where there is no apparent collar, the dorsolum (dorslet) is the first piece of the mesothorax, and where there is one, the second; it bears the elytra or other primary organs of flight. It varies in the different Orders, particularly with respect to its exposure. In Coleopterous insects it is most commonly, but not invariably[1652], covered entirely by the shield of the prothorax, the scutellum alone being visible; as it is also in the Orthoptera (with the exception of Mantis and Phasma, in the first of which it is partially, and in the latter intirely exposed), and the Heteropterous, and most of the Homopterous section of the Hemiptera. The scutellum is likewise covered in Gerris, Hydrometra, and Velia, and the whole of the back of the alitrunk by a process of the prothorax in Acrydium F., Centrotus, &c. But in the remaining Orders, and the tribe of Tettigonia in the Homopterous Hemiptera, the dorsolum is not hidden by the thoracic shield. It is usually less elevated than the scutellum; in Necrophorus, and some other beetles, however, the latter is most depressed. With regard to its substance, it is generally not so hard and rigid as the scutellum, but in most Coleoptera harder than in the other Orders in which it is covered; in the Hemiptera, except in Tettigonia, it approaches to membrane. As to shape and other circumstances, it varies in the different Orders. In the beetle tribes it has generally a sinus taken out of its anterior margin, and it approaches more or less to a trapezium; in Blatta it is transverse and somewhat arched; in Gryllotalpa it is nearly square, and distinguished besides on each side by a minute aperture, fitted with a tense membrane, which perhaps covers a respiratory apparatus. In the locusts it is more or less triangular, and in Mantis and Phasma long and slender. In the Hemiptera the dorsolum appears to consist of several pieces, variously circumstanced, separated by sutures, corresponding with which are as many ridges on the inside of the crust[1653]. In the Libellulina it is rhomboidal[1654]; in Panorpa nearly hexagonal; in the Ephemerina it is ample and oblong; in Sialis and the Trichoptera this part is represented by three subtriangular pieces, the scutellum constituting a fourth, with the vertices of the triangles meeting in the centre[1655]; in the Lepidoptera the part in question is large, and receives the scutellum into its posterior sinus[1656]. The Hymenoptera usually exhibit a very ample dorsolum, mostly subtriangular with the vertex rounded or truncated, and pointing in some (Vespa L.) to the head[1657], and in others (Apis) to the anus; in the Diptera, except in Tipula, the parts of the mesothorax are not separated by any suture, but only indicated by impressed lines or channels; in the genus last mentioned, however, the dorsolum is distinct, subrhomboidal, and received by an angular sinus of the scutellum, which last, I think, is not the part that has usually been regarded as entitled to that denomination; for this opinion I shall soon assign my reasons.

3. Scutellum[1658]. Some writers on the anatomy of insects, looking, it should seem, only at the Coleoptera and Orthoptera, have regarded the dorsolum and scutellum as forming only one piece[1659], and others have affirmed that the Lepidoptera and subsequent Orders have no scutellum[1660]. But as we proceed in considering the scutellum in all the Orders, we shall see that both these opinions are founded on partial views of the subject, and that all winged insects have a scutellum, more or less distinctly marked out or separated from the dorsolum. In the Coleoptera the scutellum is usually the visible, mostly triangular, piece that intervenes between the elytra at their base[1661], and which terminates the dorsolum. Some Lamellicorn beetles, &c. (Scarabæidæ MacLeay) are stated not to have the part in question (exscutellati): but this is not strictly correct, for in these cases the scutellum exists as the point of the dorsolum covered by the prothorax, though it does not intervene between the elytra: in others of this tribe, as Cetonia chinensis, bajula, &c., it separates these organs at their base, though it is covered by the posterior lobe of the prothorax: in Meloe F., the elytra of which are immoveable, there seems really to be no scutellum. Generally speaking, as was lately observed, but not always, it is distinguished from the dorsolum by being more elevated: this is particularly conspicuous in the genus Elater, in which it is a flat plate elevated from the dorsolum by a pedicle; in Sagra the latter part is horizontal, while the scutellum is vertical: and even in cases where the distinction is not so striking, these parts are separated either by a line, or some difference in their sculpture and substance. In this Order this part varies greatly, and often in the same tribe or genus, both in size and shape; being sometimes very large[1662], and sometimes very minute; sometimes very long, and sometimes very short; sometimes nearly round, at others square; now oval or ovate, heart-shaped, triangular, acuminate, intire, bifid, &c. In the Orthoptera, though less conspicuous, it still is present as a triangular elevation of the middle of the posterior part of the dorsolum, with the vertex either pointing towards the head, as in Blatta, or towards the tail, as in Locusta Leach[1663]. In the Heteropterous section of the Hemiptera (which, in columns of Mandibulata and Haustellata, appear to bear the same reference to the Coleoptera, that the Hymenoptera do to the Diptera, and the Homopterous Hemiptera to the Orthoptera[1664]) the part we are considering is mostly very large and conspicuous, quite distinct from the dorsolum, and in some (Tetyra F.) covering the whole abdomen, as well as the Hemelytra and the wings; it is most commonly, as in the Coleoptera, obtriangular[1665], but in the last-mentioned genus it often approaches to a pentagonal shape. Though usually so striking a feature in this tribe, in the aquatic bugs (Gerris &c.) it is covered by the prothorax. In some species of Reduvius F. (R. biguttatus, mutillarius, lugens, &c.) it is armed with one or more dorsal or terminal spines. In the Homopterous section, where the dorsolum, as in Tettigonia F., is not covered by the prothorax, the scutellum, which is merely a continuation of that part, bears some resemblance to a St. Andrew's cross, and terminates in a fork[1666]; in Fulgora, in which it is partly covered, it is merely the triangular point of the dorsolum: in the Cercopidæ, &c., whose dorsolum is wholly covered, the triangular scutellum is distinct from it; in Centrotus, Darnis, and Membracis, in which the prothorax is producted, and covers the abdomen more or less, the scutellum is a short transverse distinct piece. In the Lepidoptera, from the difficulty of abrading sufficiently the scales and hairs without injury, it is difficult to obtain a correct idea of the part in question; in the cabbage butterfly (Pieris Brassicæ) it appears to be triangular: in the humming-bird hawk-moth (Macro-glossum Stellatarum) it approaches to a rhomboidal shape[1667]; and in the eggar-moth (Lasiocampa Quercus) it is completely rhomboidal. In the Libellulina, in the Neuroptera Order, it seems to be represented by the posterior point of the dorsolum, which terminates in something like a St. Andrew's cross[1668]. In most of the other tribes of this Order the scutellum is a triangular piece, with the vertex to the head, received between two pieces of the dorsolum; in Psocus it is nearly like that of Tettigonia before described. In the Hymenoptera the scutellum is separated from the dorsolum, which it often embraces posteriorly, as the collar does in front, by a suture; it varies occasionally in shape in the different tribes, most commonly it is crescent-shaped, but in many Ichneumonidæ and others it is triangular[1669]; in the hive bee, &c., it overhangs the succeeding piece of the alitrunk; in Melecta, Crocisa, &c., it is armed with a pair of sharp teeth[1670]; in others (Oxybelus uniglumis, &c.) with one or more spines, and in some with a pair of long horns[1671]. Before I describe this part in the Diptera, it will be proper to assign my reasons for considering a different piece as its representative, from what has usually been regarded as such, and which at first sight seems the analogue of what I admit to be the scutellum in the Hymenoptera. The dorsolum, and its concomitant the scutellum, belong to the first pair of the organs of flight, which are planted usually under the sides of the former, and in the case of wings, by their Anal Area, connected either mediately or immediately with the latter. Now, if you trace the sides of the piece that I have considered as the part in question in Hymenoptera, you will find that they lead you not to the base of the lower but to that of the upper wings[1672], and in the saw-flies (Tenthredo L.) you will see clearly that the Anal Area of these wings is attached to a process of it, a proof that it belongs to the mesothorax, or region of that pair. But in the Diptera, the part that has been usually called the scutellum is not at all connected, either by situation or as a point of attachment, with the wing itself, but with the lower valve of the alula, which is with reason thought to be the representative of the secondary wing of the tetrapterous Orders. You may see this even in the common crane-fly (Tipula), in which there is a real alula, connected by means of a lateral process, terminating in ligament, with this supposed scutellum. If you examine further the same insect, you will easily find what I regard as the true one in the bilobed piece which receives the dorsolum, situated between the wings, and to the sides of which they are attached. In Asilus, Tabanus, &c., this part is transverse, and only distinguished on each side by an oblique impressed line; in the Muscidæ it is square, and marked by a straight transverse one.

4. Frænum[1673]. This appendage to the scutellum and dorsolum varies considerably in the different Orders, and in many cases, as you will see, is a very important part, being the process by which the former is mostly connected with the elytra or upper wings. In the Coleoptera, the elytra of which are nearly stationary in flight, and therefore less require any counteraction to prevent their dislocation, this part is commonly merely a process or incrassation of the under margin of the scutellum, which towards the base of the dorsolum is dilated to form the socket for the elytra. Its use as a countercheck in this Order is best exemplified in the common water-beetle (Dytiscus marginalis). This at the inner base of the elytra has a membranous fringed alula resembling those of Diptera; to the lower fold of this the extremity of the frænum is attached, which forms a right angle with the scutellum, and the upper fold is attached to the base of the elytrum[1674]. The object of this appendage is probably to prevent the dislocation of these organs, which seems to indicate that they are used more in flight than those of other beetles. The Blattæ also, in the next Order, have a winglet attached to the anal area of the tegmina. The frænum, as in the preceding Order, lies under the margin of the scutellum and dorsolum, but which here forms one uninterrupted transverse line; it is nearly vertical, and is attached to the alula. The structure is not very different in the other Orthoptera[1675], but the frænum is surmounted or strengthened by one or two ridges; in Mantis it runs from the scutellum in an angular or zigzag direction--but in all it is attached immediately to the tegmen. In the Heteropterous Hemiptera it is represented by the narrow bead adjacent to the scutellum on each side[1676], which dilates into a flat plate as it approaches the Hemelytrum, with the Anal Area of which it is connected. But the Homopterous section of the Order in question furnishes examples of the most remarkable structure of this countercheck, which proves that it is really, what its name imports, a bridle. If you examine the great lanthorn-fly (Fulgora laternaria), or any species of Tettigonia, &c., you will find adjacent to the scutellum or parallel with it, on each side a flat plate; and from the angle of that part in the first case, and from one of its processes in the last, you will further perceive a ridge or nervure which runs along this plate, in one forming an angle, and in the other being nearly straight, to the base of the tegmen, where it becomes a marginal nervure to a membrane that is attached to the posterior part of the base of the Anal and Costal Areas; and that this marginal nervure, like a trachea, consists of a spiral thread, or rather of a number of cartilaginous rings connected by elastic membrane[1677], and consequently is capable of considerable tension and relaxation, as the tegmen rises and falls in flight. In the Lepidoptera it appears to be a short piece overhung by the scutellum, which as it approaches the base of the wing is dilated. In the Libellulina, to go to the Neuroptera, it has the same kind of elastic nervure connected with the Anal Area of the wing which I have just described in the Homopterous Hemiptera; another nervure, in Æshna at least, appears to diverge upwards from the scutellar angle to the Intermediate Area[1678]: a structure little different distinguishes the rest of the Neuroptera, and even the Trichoptera. In the Hymenoptera this part varies somewhat; in the majority perhaps of the Order, as well as in the Diptera, it appears to be merely the lateral termination of the scutellum where it joins the wing; but in some tribes, as in Tenthredo L. (especially Perga Leach), Sirex L., and the Ichneumonidæ, a ridge, and sometimes two, runs from the scutellum to the wing; the upper one, where there are two, as in Perga, being the stoutest, and connecting with the Costal Area, and the lower one with the Anal.

5. Pnystega[1679]. We learn from M. Chabrier, that in the common dragon-fly, a space, consisting of three triangles, which immediately succeeds the frænum, affords attachment to no muscles, but merely covers aërial vesicles[1680]. This is the part I have called the pnystega[1681]. An analogous piece may be discovered in Phasma and Mantis in a similar situation; but I cannot trace it in Locusta Leach, or in the other Orders.

* * * * *

Having considered the parts that constitute the mesothorax, we will next say something upon those, as far as they require notice, that compose the medipectus or mid-breast. But first I must observe, in general of the medipectus and postpectus taken together, or the whole underside of the alitrunk, that though usually they are in the same level with the antepectus or under side of the manitrunk, yet in several instances, as the Scarabæidæ MacLeay, the Staphylinidæ, &c. they are much more elevated than that part; they are also usually longer, very remarkably so in Atractocerus, but in Elater sulcatus and many others they are shorter. These parts are also commonly rather more elevated than the abdomen,--much so in some, as Molorchus; but scarcely at all in others, as Buprestis, the Heteropterous Hemiptera, &c. In some of the latter (Tetyra F.) the abdomen seems the most prominent. Another observation relating to this part must not be omitted, namely, that though in many cases the medipectus and postpectus are perfectly distinct and may be separated, yet in others, as for instance the Lamellicorn beetles, the Hymenoptera and Diptera, &c., no suture separates them; so that though the upper parts, the mesothorax and metathorax, are separable, the lower ones just named are not so.

6. Peristethium[1682]. The first piece of the medipectus is what I have called, after Knoch, the peristethium[1683]. This immediately follows the antepectus; on each side it is limited by the scapulars, and behind by the mid-legs and mesosternum. Its antagonist above is usually the dorsolum. In the Coleoptera Order it varies occasionally, both in form and magnitude, but not so as to merit particular notice, except that both are regulated by the scapulars--if these are small, the peristethium is ample; and, vice versa, if they are large it is small. In all the following Orders, except the Hymenoptera, it is equally inconspicuous, but in them it is often more remarkable. I have a Brazilian species of Cimbex (C. mammifera K. MS.) which appears undescribed, in which this part swells into two breast-like protuberances, terminating posteriorly in membrane, as if it had separate motion: in the golden-wasps (Chrysis L.) it is anteriorly concave to receive the coxæ of the mid-legs; and in Stilbum, of the same tribe, it is armed with one or more conical obtuse teeth.

7. Scapularia[1684]. The scapulars are situated between the coxæ of the mid-legs and the base or axis of the upper organs of flight, and they seem to act as a fulcrum to each. In the Coleoptera Order they are most commonly quadrangular or subquadrangular, often divided diagonally, and sometimes transversely, by an impressed line; the posterior part, which is usually the most elevated and often has an uneven angular surface, is that which intervenes between the coxæ and elytra: where the former are short, as in the Capricorn beetles, the scapulars are long; and where they are long, as in the Petalocerous ones, the latter are short. The anterior part is that which forms the lateral limit of the peristethium, upon which it often encroaches: this part, in conjunction with the dorsolum above, and the last-named part below, forms the kind of rotula that plays in the posterior acetabulum of the manitrunk, as the head does in the anterior one. In the flower-chafers (Cetonia F.) the scapulars are very thick and elevated, and interpose between the posterior angles of the prothorax and the shoulders of the elytra, which is one of the distinguishing characters of that tribe: in this case the lower angle of the scapular connects with the coxa of the mid-leg, and the upper angle with the axis of the elytra; and the most elevated and thickest part of the scapular is about midway between the two. This robust structure seems to indicate that the scapular has to counteract a powerful action both of the leg and elytrum. In the Orthoptera the scapulars are usually divided into two parallel pieces, corresponding probably, though more distinct, with the two parts lately noticed of those of the Coleoptera: the upper side of the socket of the mid-leg is common to the base of both these pieces, but the articulation of the tegmen is chiefly with the anterior one. In the grasshoppers, locusts, &c. (Gryllus L.) in which tribe this leg is nearly opposite to that part, the scapular inclines but little from a vertical position[1685]; but in the praying-insects (Mantis), spectres (Phasma), and cockroaches (Blatta), in which the insertion of the mid-legs is behind that of the tegmina, it is nearly horizontal. In the Heteropterous Hemiptera the anterior part of the scapular is covered by the antepectus, and separated by a ridge, more or less pronounced, from the open part; the whole is of an irregular shape, and nearly parallel with the parapleura. In the Homopterous section it likewise consists of two pieces, and sometimes of more. Thus in Tettigonia F. it is bilobed, and between it and the coxa two small pieces are inserted[1686]. In some others, Iassus Lanio F., &c., it is not very unlike the scapular in Coleoptera, being subquadrangular and divided diagonally. In the Neuroptera this part and the parapleura are parallel, and placed obliquely[1687]. In the common dragon-fly (Æshna viatica) the former forms nearly a parallelogram[1688], which is not divided by any ridge or channel, but its lower half is separated into two unequal parts by a black longitudinal line, opposed to which on the inside is a ridge. The mid-leg in these is connected with the scapular by the intervention of a triangular transverse anterior piece, which in fact seems only marked by a black channel, to which also interiorly a ridge is opposed[1689]. In the rest of the Order it is divided longitudinally into two parallel pieces. In Panorpa the posterior piece is longer than the anterior and props the coxa behind; in Myrmeleon and Perla, &c., it appears to consist of three pieces. I have not been able to obtain a clear idea of them in the Lepidoptera, except that they have more than one piece. Hymenopterous and Dipterous insects for the most part have no scapular distinct from the peristethium; but in Cimbex, Perga, and other saw-flies, it seems represented by its posterior depressed and sometimes membranous part: in Vespa, &c. a small subtriangular piece, just below the base of the upper wing, is probably its analogue[1690].

8. Mesosternum[1691]. The central part of the medipectus, or that which passes between the mid-legs when elevated, protended, or otherwise remarkable, is called the mesosternum or mid-breast-bone. In the Coleoptera Order it exhibits the most numerous variations, and is usually the most strongly marked of any of the three portions of the sternum, affording often important characters for the discrimination of genera and subgenera. It may be said to be formed upon three principal types--the first is, where it is a process of the posterior part of the peristethium, and points towards the anus or the head;--the second, where it is a process of the anterior part of the mesostethium, and points only towards the head: in this case there is no suture to separate the medipectus from the postpectus;--the last type is where it is a ridge formed by a process both of the peristethium and mesostethium meeting between the legs; an example of this you will see in the common dung-chafer (Geotrupes Latr.). Upon the two first of these cases I shall offer a few remarks;--the last affording no variation need only be mentioned.

If you examine the terrestrial Predaceous beetles (Cicindela and Carabus L.) you will find that the peristethium is usually flat, terminating towards the postpectus in a kind of fork, the sinus of which receives the anterior point of the mesostethium--this is the mesosternum; but in the aquatic insects of this tribe, at least in Dytiscus marginalis, &c. the structure at first sight seems different, for apparently the prosternum is received by the anterior fork of the mesostethium; but if you proceed to separate the manitrunk from the alitrunk, you will find that the true mesosternum of the usual form is quite covered by this point, which curves towards the breast, is longitudinally concave to receive the point of the prosternum, and permit its motion in the groove. In some Heteromerous beetles, as the Helopidæ, &c. this part is anteriorly bilobed, so as to form a cavity which receives the point of the prosternum when the head is bent down: in Helops nitens (Tenebrio Oliv.) this sinus represents a crescent; in Cistela Ceramboides it is shaped like the Greek letter γ; in the Lady-bird (Coccinella L.) it assumes nearly the shape of a Saint Andrew's cross; in Spheniscus K.[1692] the mesosternum is wide, concave and wrinkled, with an anterior and posterior sinus; while in the analogous genus Erotylus[1693] it is convex anteriorly, and posteriorly more or less rounded; in Doryphora it is a long, robust, subconical horn, often standing at an angle of about 45°, overhanging the prosternum.

In the genus last named, though its mesosternum in its direction and appearance resembles that of many Petalocerous beetles, yet it is separated by an evident suture from the mesostethium; but in the last-mentioned tribe its representative is a process of the latter part: yet as the peristethium and mesostethium are separated by no suture, though in some cases a transverse channel, and in others merely a coloured line, marks the point where they may be considered as soldered together, in these cases the mesosternum may perhaps be said to be common to both. In this great family, which includes within its limits some of the most singular and wonderful in their structure and armour, as well as some of the most brilliant and beautiful of the beetle tribes,--the part in question, in a vast number of cases, will enable the Entomologist satisfactorily to trace its numerous groups, not only where it rises or stretches out into a horn or ridge, but even often where it is merely a flat space between the mid-legs. I shall notice some of its most striking variations in this tribe. In Phanæus festivus, and in Macraspis and Chasmodia MacLeay, it is elongated horizontally, with the apex curving upwards; in Anoplognathus it is horizontal, straight, and figures an isosceles triangle; in Cetonia suturalis, vitticollis, &c. it is very long, passing between the arms and nearly reaching the head; in C. marmorea, Lanius, &c. it is a lofty, robust, conical prominence; and in many Rutelidæ, especially those with striated elytra, it is pyramidal or four-sided; it varies also in its termination, particularly in the Cetoniadæ; and even where there is little or no elevation of it, as in the Scarabæidæ MacLeay, it is often terminated anteriorly by lines that vary in their angle or curvature. The genus Copris, as restricted by Mr. W. S. MacLeay, may from an inspection of this circumstance be divided into several families. Thus in C. Molossus and affinities its termination represents the letter ⅄ reversed, or a triangle surmounted by a mucro; in C. orientalis, &c., it ends in an acute-angled triangle; in C. lunaris, &c. in an obtuse-angled one; and in C. Iacchus, &c., in the segment of a circle.

The part we are considering is not so important in the other Orders. In the Orthoptera, however, it is occasionally remarkable. In Acrida viridissima (Locusta F.) attached to the anterior margin of the peristethium are two long triangular pieces which appear to represent this part; in the kindred subgenus, Conocephalus[1694], it is a single piece bifid at the apex; in Gryllotalpa it is a very elevated hairy ridge; and in Locusta Leach, it is a flat anterior process of the mesostethium. In the Heteropterous Hemiptera this part is often merely a portion of the channel in which the promuscis reposes; but sometimes, as in Edessa F., it is an elevated piece varying in its termination. In the remaining Orders, as far as I have had an opportunity to examine them, it can scarcely be said to exist separately from the medipectus, except that in Tipula Latr. a bipartite subtriangular membranous piece seems to be its analogue.

* * * * *

We are now to consider the last segment of the alitrunk, which, as a whole, may be denominated the potruncus; it bears the second pair of the organs of flight, and the last pair of legs. The upper side of this is the metathorax, and its lower side the postpectus.

9. Postdorsolum[1695]. The first external piece of the metathorax is the postdorsolum, which presents itself under very different forms and circumstances in the different Orders. In the Coleoptera it is intirely covered by the dorsolum and scutellum; it is generally more or less of a membranous substance, or partly membranous and partly corneous, which enables it to yield more to the action of the wings in flight; it is usually an ample transverse piece with tumid sides[1696]; but in the Scarabæidæ MacLeay, it is short though very wide; and in Cychrus, and probably other apterous beetles, it is extremely minute and almost obsolete. In the Orthoptera Order, I observe once for all, the part in question, as well as the postscutellum and postfrænum are mere counterparts of the dorsolum, scutellum, and frænum, except that in some cases they are larger[1697]. In the Heteropterous Hemiptera at first sight it would appear that all the parts of the metathorax were altogether wanting or absorbed in the ample scutellum; but if you remove this with care, you will find under it their representatives, its lower surface being hollowed out to receive them. The postdorsolum appears in these as a transverse obtusangular band; in the Nepidæ, Notonectidæ, &c. the three parts of the metathorax seem united into a single plate, emerging laterally from under the scutellum below the frænum; in which, however, some traces of a distinction between them may be discovered. In the Homopterous section the Fulgoridæ exhibit these pieces very distinctly, covered only at the base by the mesothorax: but in Tettigonia they are not so easily detected; they exist however as a narrow strip or band, almost concealed by that part. As to the Lepidoptera Order, in Pieris Brassicæ at least, the postdorsolum is represented by a pair of nearly equilateral triangles whose vertexes meet in the centre of the metathorax, and between which and the scutellum is a deep cavity; but in Macroglossum Stellatarum and Lasiocampa Quercus, there appears to be also a central transverse piece between them. In the Neuroptera there is no material or striking difference between the parts of the mesothorax and metathorax[1698]. In the Hymenoptera more variety occurs in this part. In the saw-flies, &c. (Tenthredo L.) the postdorsolum is a transverse piece covered by the scutellum; in the Ichneumonidæ it is smaller, but not covered; in the Vespidæ it is apparent, transverse, and with the postscutellum obtusangular[1699]; in Apis it is overhung by the scutellum. The Diptera exhibit some variations in this part. In Tipula it consists of three pieces placed transversely, the central one quadrangular, and the lateral ones roundish; in the Asilidæ and most others of this Order, with the postscutellum, it forms a segment of a circle[1700], sometimes armed with a pair of spines, as in Stratyomis F., and is what has been usually regarded as the real scutellum, though, as I have endeavoured to show, not correctly[1701].

10. Postscutellum[1702]. The postscutellum bears the same relation to the postdorsolum that the scutellum does to the dorsolum, but it is seldom, if ever, a distinct piece. In the Coleoptera it is represented by the longitudinal narrow channel that terminates the postdorsolum towards the anus[1703]: this usually figures an isosceles triangle with the vertex truncated or open; but in Copris the triangle is equilateral. In the other Orders it is little more than the central posterior point of the postdorsolum[1704].

11. Postfrænum[1705]. The part now mentioned is much more important than the preceding one, and must not be passed over so cursorily. In the Coleoptera it usually presents itself under the form of two large and usually rather square panels, the disk of which is convex, but the rest of their surface unequal, which are situated one on each side of the postscutellum[1706]; under the anterior outer angle of these is the socket or principal attachment of the secondary wings, and their basal margin is attached to their outer side; posteriorly behind the vertex of the postscutellum the postfrænum is crowned with a ridge or bead, below which it descends vertically or obliquely to the abdomen; this ridge often turns upwards, and proceeds towards the middle of the basal margin of the wing. In the Petalocerous beetles the part in question is usually more or less hairy; but in many others, as the rose-scented Capricorn (Callichroma moschatum), &c. it is naked. At its side you will commonly observe several plates and tendons (osselets Chabr.) connected inter se and with the base of the wing by elastic ligaments, which are calculated to facilitate the play of those organs. In the Orthoptera, Neuroptera, and Homopterous Hemiptera, the postfrænum does not differ materially from the frænum[1707]. In the Heteropterous section of the last Order it is usually a transverse ridge terminating the postdorsolum, with a bifurcation where it unites with the wing; but in Tetyra F. (at least so it is in Tetyra signata,) it is a nearly vertical piece, marked in the centre with an infinity of very minute folds, which probably by their alternate tension and relaxation let out and pull in the wings. Amongst the Lepidoptera it is not remarkable. In the Hymenoptera Order it is mostly represented, I think, by a double ridge or fork, sometimes however obsolete, but very conspicuous in the saw-flies, which laterally terminates the postdorsolum; the upper branch, usually the thickest, going to the anterior part of the base of the underwing, and the lower one to the posterior. You may observe something similar in the crane-flies (Tipula Latr.) and Asilidæ. A tendon proceeding from the point of the postscutellum forms a fork near its end, the upper branch of which connects with the anterior and the lower with the posterior valve of the winglet; the structure is a little, but not essentially, different in other Diptera.

12. Pleura[1708]. By this name I would distinguish the part which laterally connects the metathorax and postpectus. It includes in it the socket of the secondary wings. In the Coleoptera this is a two-sided piece lying between the postfrænum and the parapleura, with the upper side horizontal and the lower vertical[1709]--a tendon usually proceeds from its anterior extremity to the base of the wing. In the Orthoptera, Neuroptera, and other Orders, it is merely the longitudinal line of attachment of that part; but in the genus Belostoma Latreille, related to the water-scorpion, it presents a peculiar structure, being a deep channel or demitube, filled at its posterior extremity by a spiracle and its appendages[1710].

13. Metapnystega[1711]. This part, although in the table I have placed it as an appendage of the pleuræ, is not always confined to them, as you will soon see. It either covers aërial vesicles, or is the seat of a spiracle. In the Order Coleoptera it is of the former description. If you examine the metathorax of the common dung-chafer (Geotrupes stercorarius), in the horizontal part of the pleura you will see a sublanceolate or subelliptical rather membranous silky tense plate, with its point towards the head,--this is the part we are considering; something similar you will find in most beetles; but in some, as Callichroma moschatum, it is less conspicuous. This part, as far as I have observed, is not so situated in any other Order, except in some Heteropterous Hemiptera: in Belostoma the channel lately mentioned is filled up at its posterior end by a red organ with an anterior vertical fissure, terminating behind in a conical bag: in Notonecta the pleura has something of a plate like that of Coleoptera, but of a horny substance. In the Orthoptera and Neuroptera this part changes its situation, if it be indeed synonymous; and as the pnystega follows the frænum, so the metapnystega succeeds the postfrænum. In the Libellulina M. Chabrier found that this as well as the other covered aërial vesicles[1712], and it probably does the same in the other cases in which it occurs. In Mantis and Phasma in the Orthoptera it is very minute; but in Locusta Leach, it is more conspicuous under the form of a tense membrane, the surface of which is depressed below that of the abdomen: in Acrida viridissima K. it fills the sinus of the postfrænum, and is vertical, as it is in Æshna. It is worthy of remark that this piece bears some analogy to that below the ridge of the part just named in Coleoptera, which descends either vertically or obliquely to the abdomen[1713]. A similar space, though often nearly obsolete, may be seen in the Hemiptera and Lepidoptera. But the Orders in which this part is most conspicuous are the Hymenoptera and Diptera, and in these its aërial vessels are connected with a spiracle. In Tenthredo L. and Sirex L., what Linné named grana, from their situation, should be regarded as belonging to the pnystega, and whether there is any part representing the metapnystega I am not quite satisfied; perhaps the membrane at the base of the abdomen in Tenthredo, and the bipartite piece, apparently its first segment, in Sirex[1714], may be its analogues: but in the great majority of the Order, the convex or flat piece that intervenes between the postdorsolum and its adjuncts and the abdomen, and which bears a spiracle on each side, is the metapnystega[1715]. This part is often remarkable, not only for its size, but for the elevated ridges that traverse it, as in Ichneumon, Chlorion, &c. In the last genus it is of a pyramidal shape, with the anterior part horizontal and the posterior vertical; it is altogether vertical in Vespa, Apis, &c. Amongst the Diptera, in Tipula it is nearly horizontal, and shaped like a cushion; but in general in this Order it is vertical, and concealed under the postdorsolum[1716].

* * * * *

We are now to consider the parts that constitute the postpectus or under-side of the metathorax, and which bears the posterior pair of legs.

14. Mesostethium[1717]. This part in Coleoptera is terminated anteriorly by the peristethium, scapulars, and mesosternum, laterally by the parapleuræ[1718], and behind by the coxæ of the posterior legs[1719], which generally are inserted transversely between it and the abdomen. It is commonly very wide; but in Dytiscus L., Carabus L., &c., in which the coxæ and parapleuræ are dilated, it is proportionally reduced: its length is regulated by the distance of the intermediate and posterior legs; where these are far asunder, as in the rose-scented Capricorn (Callichroma moschatum), &c. it is long: but where they are near each other, as in the Scarabæidæ MacLeay, it is short; its width, however, generally exceeds its length. In shape it is generally subquadrangular[1720], though sometimes rhomboidal, and other forms of it occur. Between the hind-legs it generally terminates in a notch or bifurcation distinct from the metasternum, as in Hydrophilus, &c.; in Hister there is no notch, and in many Scarabæidæ it projects between the hind-legs in a truncated or rounded mucro; in the Vesicatory beetles, Meloe L., it is more elevated than the medipectus, towards which it descends almost vertically; in Dytiscus L., Carabus L., &c., this part is usually divided into two by a transverse sinuous channel, and in Elater by a longitudinal straight one. In many Orthopterous genera, Gryllotalpa, Acrida K., Locusta Leach, &c., the mesostethium consists of two pieces[1721]. It is remarkable that in many of these genera, in this part, as likewise in the medipectus and antepectus, are one or more perforations which appear to enter the chest, the use of which I shall explain hereafter. In the Libellulina, as I shall soon have occasion to shew, there is a peculiar arrangement of the legs and wings, in consequence of which this part is placed behind the posterior ones. In the remaining Orders, the mesostethium, though it exists, exhibits no peculiarities worthy of particular notice, except in some Aptera and Arachnida: thus, in Nirmus Anseris it is terminated posteriorly by a pair of transverse membranous appendages which cover the base of the posterior coxæ; in Scorpio it consists of two pieces, the pectines[1722] being attached to the sides of the posterior one.

15. Parapleura[1723]. The parapleura, speaking generally, is that piece of the postpectus which, intervening between the pleura, mesostethium, and scapulars, is attached by its posterior extremity to the coxæ of the hind-legs; by means of the pleura, from which it does not appear to be separated by any suture, it connects the secondary or under-wings with the hind-legs, as the scapular does the primary ones with the mid-legs; so that the direction of the parapleura depends upon the relative situation of the legs and wings. In Coleopterous insects its direction is horizontal, it being generally a narrow subquadrangular piece that runs straight from the posterior coxæ to the scapular[1724], and usually divided into two unequal portions by an elevated or impressed line. In the palm-weevil (Calandra Palmarum) this part is wider than usual; in Dytiscus marginalis,--in which genus, as likewise in Carabus L., the coxæ are incapable of separate motion,--it is nearly a right-angled triangle, and is divided longitudinally into two unequal portions. In the Orthoptera Order this part usually consists of two equal portions, and its direction is sometimes nearly horizontal, as in Mantis and Phasma; sometimes forming an angle with the horizon, as in Blatta; and sometimes nearly vertical, as in Locusta Leach. In the two first cases the wings are before the legs, and in the last their position is over them. In the Heteropterous Hemiptera it is parallel with the scapular, is divided into two unequal portions, and its direction is more or less inclined to the horizon[1725]. As to the Homopterous section--in Fulgora it is of a very irregular shape with an angular surface, and its direction from the leg to the wing is first nearly vertical and then horizontal: in Tettigonia it is almost vertical, and consists of two nearly equal portions. To come to the Neuroptera--in the Libellulina it consists of two pieces, like those of the scapulars, but smaller[1726], and its inclination is towards the head: in Panorpa also it resembles the scapulars both in form and other circumstances[1727]. In the remaining Orders it exhibits no very remarkable features.

16. Metasternum[1727]. The central part of the mesostethium when elevated or porrected, or otherwise remarkable, is called the metasternum. In the Coleoptera, in those cases, as we have seen above[1728], in which the medipectus and postpectus form one piece, its anterior point becomes the mesosternum; but in others, as the Predaceous and Capricorn-beetles, &c., it is received in a sinus or fork of that part, or meets it. It is usually neither so remarkable nor important as the mesosternum. In Bolbocerus K. it is a rhomboidal elevation: in Gyrinus a ridge; as also in many Hydrophili, in which it passes between the hind-legs to the abdomen, and terminates in a sharp point[1729]; and in Dytiscus its two diverging lobes cover the base of the posterior trochanters[1730]. In the Orthoptera Order this part is not remarkable; but in Acrida viridissima K. it consists of three triangular pieces, the lateral ones being erect, and the intermediate one horizontal: in Locusta Leach it resembles the mesosternum[1731]. In the Heteropterous Hemiptera the whole mesostethium is elevated, and terminates at both ends in a fork, the anterior one receiving the point of the promuscis, and the posterior one that of the epigastrium: in the Homopterous section, the Tettigoniæ F. have usually a distinct metasternal point between their hind-legs. In the remaining Orders there is no metasternum, or no remarkable one, except in one singular Hymenopterous genus, Evania, the parasite of the Blattæ[1732], in which there is a forked posterior process of the mesostethium with recurved points.

17. Opercula[1733]. By this term I distinguish those plates, before largely described[1734], which cover the drums of male Tettigoniæ F.; and likewise those called also by the same name by M. Chabrier[1735], which cover, in many cases, the vocal apparatus of the trunk of insects: those of Melolontha vulgaris he describes as situated below the wings, and between the two segments of the alitrunk[1736]; and if you take this insect and remove the elytra, the mesothorax and scapulars, under the latter and below the wing you will find an oval convex plate, which is probably the part he is speaking of;--but it is better exemplified, I think, in the common Dytiscus marginalis, in which it is very distinct as a convex subtriangular plate connected with the metathorax by membranous ligament, covering a kind of pouch, and appearing to open and shut at the vertex[1737].

* * * * *

I must here observe, with regard to the Aptera and Arachnida, that the trunk in them is much more simple than in those insects that are furnished with wings. In the hexapods, in the former Orders, though there are usually three pedigerous segments, there is no distinction of dorsolum, scutellum, &c. In the Scolopendridæ and Scutigera amongst the Myriapods, according to the acute observations of M. Savigny[1738],--on which, however, some doubt at present rests,--there is a remarkable formation, the whole thorax being represented by the single plate that follows the head, to the under-side of which are attached the first and second pair of palpi or pedipalpi, and the first pair of legs, representing the three pairs of legs of hexapods. In the Iulidæ the three segments that follow the head, each bear a single pair of legs, while all the rest bear a double one: from whence it should seem to follow, that these segments and their legs represent the trunk and legs of Hexapods. In the Octopod Aptera and the Arachnida the trunk consists of a single piece, not separated from the head, and sometimes not distinct from the abdomen.

V. Internal processes[1739]. Perhaps you will think that this head would be better considered when I treat of the Internal Anatomy of Insects; but as the parts included under it are really processes of the external integument of the trunk, it seemed to me best to treat of them under that head. They are of two descriptions; processes of the thorax or upper part of the trunk, and processes of the breast or its under part.

i. Processes of the thorax[1740]. These are the phragma, prophragma, mesophragma, and metaphragma. The first belongs to the prothorax, the second to the mesothorax, and the two last to the metathorax; each forming a kind of chamber of the under-side of each segment of the thorax.

1. Phragma. The phragm, or septum of the prothorax, is most conspicuous in the mole-cricket (Gryllotalpa), in which it is a hairy ligament attached to the inside of the upper and lateral margins of the base of that part: inclining inwards, it forms the cavity which receives the mesothorax. It is not, however, without a representative in many Coleoptera, though in these it is less striking, from its being smaller and taking a horizontal direction. In Elater, by means of some prominent points received by corresponding cavities of the vertical part of the base of the elytrum, it forms a kind of ginglymous articulation, which probably keeps them from dislocation in repose, and, by the sudden disengagement of these points from the cavities, assists the animal in jumping[1741].

2. Prophragma[1742]. This is a piece usually almost vertical, but in Elater horizontal; of a substance between membrane and cartilage, descending anteriorly from the dorsolum, and forming the first partition of the chest of the mesothorax; it is generally much shorter than the mesophragm. Though very visible in Coleoptera and the Heteropterous Hemiptera, in the other Orders it is less easily detected, and is sometimes obsolete. It may be observed here, that in the Hymenoptera, at least in the wasp, the hive-bee, the humble-bee, and the Diptera mostly, the interior of the upper-side of the alitrunk, instead of two, seems at first to be divided into four chambers, formed by septula: but as these ridges merely mark out the internal limits of the dorsolum, scutellum, postdorsolum, and metapnystega, the last but one of these being usually less distinct, they seem not analogous to the three partitions of the alitrunk in other Orders; so that in these the mesophragm at least seems to have no representative, and the prophragm and metaphragm include between them only one ample chamber. In the Diptera, wherever there is an external depression or suture there is a corresponding internal ridge or seam, so that the parts seem more distinctly marked out on the inside than on the outside of the crust.

3. Mesophragma[1743]. This piece also, which forms the middle partition of the upper part of the cavity of the alitrunk, dividing it into two chambers, is most conspicuous in Coleoptera. It is usually in them a vertical piece, resembling the prophragm in substance, but twice its height, of a quadrangular shape with a notch in the middle; it fills the sinus of the postdorsolum, the sides of which sometimes descend below it[1744]. In this Order the chamber that it forms with the prophragm is very small[1745], the motions of the elytra requiring no powerful apparatus of muscles; but that which it forms with the metaphragm, which is appropriated to the muscles moving the wings, is very large[1746]. In the Orthoptera the anterior chamber is larger than in the preceding Order, which proves that tegmina are more moved in flight than elytra. In the Heteropterous Hemiptera a remarkable variation takes place--the anterior being larger than the posterior chamber; which last, in fact, consists of two, one for each wing: in these the mesophragm towards the abdomen forms an angle, which in Pentatoma, &c., is acute; in Belostoma a right angle, and in Notonecta an obtuse one. In the two first the angle of the mesophragm sends two short diverging ridges to the metaphragm; and in the last only a single one: in this also the posterior chambers together are nearly as large as the anterior. From this structure it should seem that in flight the Hemelytra are more important than the wings. In the Homopterous section the anterior chamber is the smallest, at least in Fulgora candelaria; and the mesophragm is lofty and bipartite. In the Lepidoptera the anterior chamber is the largest, and the part in question conspicuous[1747]. In the Libellulina and Hymenoptera it is merely represented by a low ridge, and in the Diptera it seems evanescent.

4. Metaphragma[1748]. This, in many cases, is the largest and most remarkable of the three partitions of the upper portion of the cavity of the alitrunk, which separates it from that of the abdomen; it is attached to the posterior margin of the metathorax, and is nearly vertical: in substance it may be stated as rather firmer than the two preceding partitions. In the Coleoptera it is commonly of the width of the posterior orifice of the alitrunk; and its centre is cleft so as to form a deep sinus[1749] for the transmission of the intestines,--a circumstance which also, though less conspicuously, distinguishes the mesophragm[1750]: from this sinus it slopes gradually towards the sides, and is sometimes armed with an intermediate process on each side[1751]. This structure you will find exemplified in the common cock-chafer and many others of the Order. I have not, however, discovered traces of it either in the Silphidæ, Staphylinidæ, or the vesicatory beetles (Meloe L.); or even in such species of Carabus L. and Cicindela L. that I have examined; while in Dytiscus it is very visible. In the Orthoptera it is nearly obsolete; but in Locusta Leach, under the metapnystega, one on each side, is a pair of seemingly pneumatic pouches which may be mistaken for it. It is almost equally inconspicuous in both sections of the Hemiptera. As to the Lepidoptera,--in Pieris Brassicæ, it resembles in some degree, though in miniature, the metaphragm of the Coleoptera; but in Sphinx Stellatarum and Lasiocampa Quercus it has a sinus on each side, but no middle one. In Panorpa it nearly closes the posterior orifice of the trunk, but in the Libellulina it is a mere ridge. In some Hymenoptera, as Cimbex sericea, the drone-bee at least, &c., it is a large convex bifid piece. In the wasps, under the spiracle of the metapnystega on each side, as in the Locusta, is what I also take to be a pneumatic pouch, which might easily be mistaken for a metaphragm. In the Diptera Order this part is very conspicuous. If you remove the abdomen of any common Tipula, you will find that the posterior orifice of the trunk is closed above by a pair of oblong, vertical, convex, diverging plates;--do the same by any fly (Musca L.), and you will detect in the same situation a very large convex or gibbous one notched below, which occupies almost the whole orifice: this is the metaphragm.

5. Septula[1752]. These are the smaller ridges of the interior of the alitrunk, which afford a point of attachment to many muscles, and run in various directions both on the interior of the crust and of the metaphragm. These little seams are not to be found so generally in the other Orders; but very frequently, as has been before observed, where there is an exterior impression of the crust, or a suture, one of these forms its internal base.

ii. Processes of the pectus[1753]. We are next to consider the internal processes of the breast of insects: these consist for the most part of the endosternum, or internal sternum, and its branches. As the principal feature of this are the processes which rising from it serve as points of attachment to the muscles that move the legs, &c., I shall confine myself to them--they are, the antefurca, the medifurca, and the postfurca.

1. Antefurca[1754]. The first portion of the endosternum, or the internal prosternum, branches into the antefurca. In the Coleoptera a plate varying in shape and direction[1755] sends forth a pair of mostly vertical processes of a cartilaginous substance[1756], differing in height in different genera. In Carabus L. there is neither this plate nor its processes; but in Dytiscus the latter are very visible. A very singular and complex machine represents the part we are considering in that extraordinary insect the mole-cricket (Gryllotalpa Latr.). When we look at its prodigious arms and consider their office[1757], we may imagine that the requisite apparatus for moving them must be very powerful and peculiar. Their CREATOR has accordingly provided them with a machine for this purpose more than usually complex, extending from the prothorax to the prosternum; the former being its base, and the latter its vertex. The cavity of the manitrunk is divided longitudinally by a double cartilaginous partition surmounted by a bony frame, with an anterior condyle or tuberosity, with which the inner part of the base of the clavicle of the arm appears to ginglymate; and the manitrunk is preserved from the injury the powerful action of the arm might occasion, by the counteraction of this machine, to describe which fully, would demand more space than I can afford[1758]. I mentioned under the mesostethium, the apertures visible in the breast of Locusta Leach and Acrida K. Each of these apertures opens into an internal, tubular, horny, process, which arching off is attached at the other extremity to the sides of the trunk--a pair being appropriated to each segment; the first analogous to the antefurca, the second to the medifurca, and the last to the postfurca. In the medipectus and postpectus of Acrida viridissima there is only a single aperture, terminating in a single tube, which after rising vertically a little way sends off a branch on either hand to the sides of the trunk. Where there are three of these holes, as in the antepectus and medipectus of Locusta Dux, there are three of these processes, the intermediate one being vertical. In the subsequent Orders the processes of the endosternum are not sufficiently remarkable to require particular notice: my further observations upon them will therefore be confined to the Coleoptera Order.

2. Medifurca[1759]. This part, which belongs to the mid-legs, is in many cases more conspicuous than the antefurca. In Copris Molossus the endosternum of the medipectus is represented by a transverse zigzag ridge[1760] between the sockets of the mid-coxæ, from which proceeds a pair of branches wide at the base and growing gradually more slender to the extremity[1761], which is attached to the sides of the trunk; in Dytiscus marginalis a pair of slender, vertical, straight processes, fitted with a broad cartilaginous plate at their apex, rises from the endosternum, and sends forth a lateral one to the side of the medipectus: and lastly, in Carabus the medifurca is represented by a pair of subtriangular laminæ attached to the sides of the trunk.

3. Postfurca[1762]. This, which belongs to the hind-legs, is the most remarkable of the pectoral processes, and has been noticed by more than one writer[1763]. It is a kind of trident, the branches[1764] of which are acute, and on their upper surface longitudinally concave, elevated on a footstalk[1765] inclined towards the medifurca, consisting of two plates, a posterior one supporting the lateral branches, and an anterior or interior one forming a right angle with the other, supporting the intermediate one. This footstalk rises from between the posterior coxæ, which appear in the Lamellicorns to ginglymate with it at its base. The middle branch of the trident dips to the sinus of the medifurca. In Dytiscus marginalis the form is different; for the intermediate branch consists of two parallel pieces, and the lateral ones are dilated into broad vertical plates: the stalk of this is triquetrous, and a triple cartilaginous partition appears to go from its base anteriorly, the lateral ones diverging to the sides of the trunk, and the intermediate one running straight to the base of the medifurca.

It may not be without interest to state here some of the several objects and uses of this structure of the trunk. When our Saviour says to his disciples, "But even the very hairs of your head are all numbered"[1766]--he taught them that the attention and care of the DEITY were not confined to the mighty and the vast, but directed to every atom of his creation--that he not only decreed the number and magnitude of the planets and planetary systems, and of their various inhabitants, but that the most minute and apparently insignificant part of each individual, both as to its number and form, was according to the law by him laid down; and whoever studies them with attention will find that insects furnish a very interesting homily upon this text; since in various instances I think I have made it clear, that parts seemingly of the least importance--as a hair, a pore, or a slight impression--have their appropriate use[1767]. At first, it would seem that the various pieces of which we have seen the second primary segment of the trunk of these animals to be composed, would be of little importance; but when we reflect that this multiplicity of parts is usually not to be found in those that have no wings, whether they be apterous sexes or tribes[1768], a suspicion arises in the mind that they must be of more consequence than their prima facie appearance seems to warrant:--and this is really the case. The manitrunk, which is destined principally to incase the muscles that move the arms, did not require to be so complex as the part that had to support the action of wings as well as legs. In those that have a large prothorax, as the Coleoptera, it may, indeed, be useful in flight as a counterpoise to the abdomen; and since when the wings descend it rises, and vice versa, it may be of some service by its vibrations[1769]; but for this it required no complexity of structure. But not so the alitrunk: it consists of parts much more numerous, and this number of parts is of great importance to the animal in its flight. All of them are so put together, being lined by a common elastic ligament[1770], as to be capable of a certain degree of tension and relaxation, which enables the animal to compress or dilate the trunk as its necessities require. To cause the elevation of the wings, it must be compressed or have its longitudinal diameter increased, and its vertical and transverse diminished: this compression is produced by the condensation of the internal air, which parts with some of its caloric, and by the action of the levator muscles. To cause the depression of the wings, it must be dilated, or have its longitudinal diameter diminished, and its vertical and transverse increased, which is effected by the rarefaction of the internal air, and the action of the depressor muscles[1771]. In some Orders, the Coleoptera, &c., this effect is promoted by the segments of the trunk, which are attached by loose ligamentous membranes, and received, one or more of them, into each other, which facilitates the above action[1772]. Thus much for the general use of these parts. I shall further here mention a partial one of two of them which seems indicated by a particular circumstance, and upon which a theory may be built. In some insects the primary and secondary wings or their analogues are placed before the legs, in others over the legs, and in others behind the legs: but whatever their position, the pieces which I have named the scapularia and parapleuræ invariably connect the one with the other; the former, the primary wings with the mid-legs, and the latter, the secondary wings with the hind-legs. This circumstance seems to prove that the wings by the intervention of these pieces have an action upon the legs, and the legs upon the wings; and this is further proved in one case by an observation of M. Chabrier with regard to Melolontha vulgaris,--that the levator muscles of the wings, by means of a long tendon, are attached to the lower part of the posterior coxæ[1773]. Now, more than one medical friend has suggested to me, that what are called the coxæ in insects are really analogous to the thighs of vertebrate animals[1774]: consequently these parts must represent the coxæ; whence it would seem that the wings are really appendages of the legs. It must, however, be observed, that were this opinion admitted, in the Aptera, Hymenoptera, and Diptera, or even in the prothorax of other insects, there would scarcely be any analogue of the coxæ at all distinct from the trunk itself, of which even in the other Orders these pieces are component parts. An instance occurs in the Strepsiptera K., and in which the arms are furnished with an alary appendage, and the metathorax has none[1775].

VI. Organs of Motion. We are next to consider those organs attached to the trunk of insects which are instruments of motion. These are principally those by which they are transported through the air, and those by which they move on the earth or in the water--their wings and their legs. I shall begin with the first, the wings[1776]. These are not formed precisely after any type at present discovered in vertebrate animals: in some respects they have an analogy to those of birds[1777]; in others, to the dorsal fins of fishes: but, perhaps, altogether they approach the nearest to those of the dragon or flying-lizard (Draco volans L.), which do not, as in birds, replace the fore-legs, are kept expanded by diverging bony rays, and are connected with the hind-legs[1778]. As the Divine Creator appears in his works to proceed gradually from one type of structure to another, it has been supposed by a learned physiologist of our own country, that in winged insects, four of the legs of the Decapod Crustacea are represented by the four wings[1779]: this opinion, however, is not yet fully proved; a remark which may also be applied to a more recent one of a celebrated French writer, who seems to think their origin and structure aërostatic, that they are auxiliary to the legs, and borrowed in part from the respiratory organs[1780]. Were I disposed to enter into these subtile speculations, I might here recall your attention to the analogy that, in their metamorphoses, exists between the Saurian Reptiles or lizard tribe and insects, and conjecture that the wings of the Draco are really representatives of the mid-legs of Hexapods, thus preparing to disappear altogether; but I shall content myself with throwing out this hint, which you are welcome to pursue. The organs of flight in general may be considered as to their number, kinds, and composition.

i. Number. The most natural number is four, for this obtains in the majority. In almost every Order, indeed, there occur instances of insects that have solely a single pair or none[1781].

These, however, are only exceptions to the rule; but in the Diptera, unless we consider the alulæ, the representatives of the secondary wings[1782], as a distinct pair, there are never more than two wings, and one instance is known in which an insect of this Order has none[1783]. Certain genera or individuals of the Tetrapterous Orders are also furnished with alulæ: besides Dytiscus, Blatta, Phalæna hexaptera, which have been before noticed[1784], they may be detected in miniature in Ammophila K. and affinities; these all may be regarded in some slight degree as insects with six wings.

ii. Kinds. Under this head we may consider the organs of flight as to their situation and as to their substance. As to their situation, usually the first pair are attached to the mesothorax, and the second to the metathorax; but in one instance, as has been before observed[1785], in the Strepsiptera K., the anterior pair belong to the manitrunk, and the posterior to the mesothorax. As to their substance, they take the several denominations of elytra, tegmina, hemelytra, and wings, for the most part according to its variations, as will be seen more at large hereafter. Under this head I shall only further observe, that in many instances the organs of flight appear to be mere abortions or rudiments, which serve to exemplify what has been more than once stated, that the CREATOR has seen it good to approach to new organs gradually as well as to new forms. Thus elytra are mere rudiments that do not serve to protect the wings in Atractocerus; tegmina in some species of Phasma, Acrydium, &c.; hemelytra in the bed-bug[1786]; wings in many female moths, in Cryptus hemipterus a Hymenopterous insect, &c.

iii. Composition. The structure of wings has been before explained to you[1787], and I shall again have occasion to allude to it; but here I wish to call your attention to a circumstance that has not hitherto, that I recollect, been adverted to; I mean that all kinds of organs of flight, and it may be traced as we shall soon see even in elytra, are divided longitudinally into three areas or folds; the first or external one I call the Costal Area[1788] from its beginning with the costal nervure; the second is the Intermediate Area[1789]; and the third is the Anal Area[1790].

Having made these observations with respect to the organs of flight in general, I shall now proceed to consider more at large the elytra, tegmina, hemelytra, and wings.

i. Elytra. These are the wing-covers of the Coleoptera Order, distinguished from tegmina by the absence of nervures, from hemelytra by the want of the membrane at the apex, and from both by their uniting in almost every instance at the suture. I shall consider them as to their substance; articulation with the trunk; expansion; parts; shape; appendages; sculpture; clothing; colours, and uses.

1. Substance. The firmness of the substance of elytra is usually regulated by that of the crust of the insect to which they belong; in hard insects they are hard, and in soft ones they also are soft. The most impenetrable ones that occur to my recollection are those of Illiger's genus Doryphora, and the softest and most flexile those of Telephorus, Meloe and affinities. With regard to individuals, they are mostly as hard as the prothorax, and harder than the back of the abdomen. Elytra also, as far as my observation goes, are never diaphanous.

2. Articulation with the trunk. This is by means of a process of the base of the elytrum which I call the axis[1791] or pivot, attached by elastic ligaments, and certain little bony pieces (osselets Chabr.) in the socket under the side of the anterior angle of the dorsolum[1792]. You may easily remove the elytra attached to the mesothorax from Geotrupes stercorarius, which will enable you to see the mode of articulation with little trouble[1793].

3. Expansion. It is by means of the bony pieces just mentioned that the organs in question are opened and shut[1794] under the action of the antagonist muscles. In opening for flight the two elytra recede from each other, and are elevated so as not to retain their horizontal position, which would interfere probably with the play of the wings, but form an angle with the body. When they return to a state of rest, the sutures usually meet and coincide longitudinally; but in some cases when closed, as in Necydalis, &c., they diverge from each other at the apex; and in Meloe, like the Orthoptera, to which that genus approaches, one laps over the other.

4. Parts. The parts to be considered in an elytrum are the areas, the axis, the suture, the margin, the epipleura, the base and apex, the angles, and the hypoderma. At first it should seem as if an elytrum was not like other wings divided into areas; but I think upon examination it will be found that, though often nearly obsolete, these are represented in it; for the epipleura[1795] with the recurved part of the external margin seems to me analogous to the Costal Area; the inflexed part adjoining the scutellum and often going beyond it to the Anal, and the rest of the organ to the Intermediate. All this you may see in the dung-chafer, Geotrupes stercorarius. The axis[1796] or pivot by which the elytrum articulates with the trunk is generally placed about the middle of its base, but nearer the scutellar than the humeral angle, and varies in length and shape in the different tribes, but not so as to merit particular notice; it may be regarded as composed of three parallel pieces, one belonging to each area, that of the costal being the longest. In many these pieces are marked by no line of distinction, but in Macropus, &c., they may be readily traced[1797]. The suture[1798] is the internal margin of the elytrum from the point of the scutellum to the end. In many beetles the right hand suture, looking from the anus to the head, has a lower ledge or margin, and the other, one more elevated, which when they are closed lies upon the former; in some Dynastidæ there seems a kind of ginglymous structure in this part, each suture being fitted with a kind of ridge which is received by a channel of the other; in these the suture is generally marked out by an adjacent channel: but the most remarkable structure of this part distinguishes the genuine species of the genus Chlamys, in which both the sutures, except at their base, are armed with little teeth, alternating with each other like the cogs of a mill-wheel. In apterous beetles the elytra are often connate, or have both sutures as it were soldered together. The margin[1799] or external edge of the elytra is generally formed by a bead or ridge, which, except in the case of the truncated ones, in which it is straight, curves more or less from the base to the apex; this ridge is often recurved so as to form a kind of channel between it and the disk of the elytrum, as may be seen in the Dynastidæ; in some there are two parallel ridges, as in Copris; in Silpha the margin is dilated; in Helæus and Cossyphus it is remarkably so and recurved, so that, in conjunction with those of the prothorax which are similarly circumstanced, they give the animal some resemblance to a small model of a barge. Though the margin of elytra is most commonly intire, yet in some beetles, as Gymnopleurus Illig., a sinus is taken out of it; in Cetonia it often projects at the base, and in Cryptocephalus in the middle, into a lobe; in Phoberus MacLeay it is denticulated, and in many Buprestes more or less serrulated; sometimes it terminates before it reaches the apex of the elytrum in a tooth, as in many Carabi Latr. The epipleura[1800] or side-cover is that part of the organ in question, below the margin, with which it usually forms an angle, being more or less inflexed, that covers the sides of the body. It varies in different tribes, being sometimes obsolete, as in the weevils (Curculio L.); in the Capricorn beetles it is very narrow; in Carabus, &c., dilated at the base; in many Heteromerous beetles, as Blaps, Pimelia, &c., it is very wide and conspicuous; in Cossyphus it stands out a little from the abdomen, so as to form a kind of fence round it. Its shape generally approaches that of a scythe, being incurved and growing more slender towards the apex[1801]; but it is sometimes straighter and shorter. In Geotrupes and many other Lamellicorns, the base of the elytrum is nearly vertical, forming a right angle with the rest of it; it is usually transverse and straight; but in Calandra Palmarum and many Cassidæ it slants to the scutellum; in Chlamys it is sinuate, and in Elater it has a deep cavity above the axis which receives the points of the phragma mentioned before[1802]. The apex of elytra is usually acute, the angle being formed by the confluence of a curving and straight line: but there are many exceptions; for instance, in Mylabris it is rounded; in Hister obliquely, and in Necrophorus transversely, truncated; in many Capricorns it is emarginate; in others, as Macropus longimanus, it is bidentate; in some Prioni, P. cinnamomeus, &c., it terminates in a mucro at the internal angle; and in Cerambyx Batus, horridus, &c., at the external; and, to name no more, in some species of Necydalis it ends in a long acumen. The scutellar angle in insects that have a large scutellum, as Macruspis MacLeay, is obliquely truncated to admit it, but where it is small it is generally rectangular, with the angle rounded; in Buprestis vittata it is obtusangular; and in Dytiscus marginalis, &c., it is emarginate. In Cassida spinifex, perforata, &c., the humeral angle is producted into an acute lobe that stretches beyond the head, and in C. bicornis and Taurus it forms a horn at right angles with the elytrum. In general it is either rectangular or rounded, with a prominence of the elytrum within it. The sutural and anal angles exist only where the elytra are truncated at the apex. In this case the sutural is generally rectangular, and the anal rather obtusangular or rounded. The Hypoderma is the fine soft membrane before noticed[1803] that lines the underside of the elytra, the use of which is probably to prevent injury to the wings from friction with their usually hard substance; this membrane is commonly of either a pallid or brownish colour; but in some insects, as Staphylinus hybridus, murinus, &c., Buprestis grandis, it is of a beautiful green or blue; and it exhibits the puncta, striæ, and other modes of sculpture of the elytra very distinctly, the pores of which usually perforate this membrane[1804]. Just under the shoulders of these organs you may observe an oblong and sometimes roundish spot, occasioned by the hypoderma in that part being particularly tense, and covering a cavity or pocket which appears to be connected with the axis by the hollow part, which I regard as representing the Costal Area; this pocket is evidently the analogue of a part in the wings noticed by M. Chabrier[1805], and named by me the phialum: from its connexion with the axis by a channel, this part in elytra should also seem destined to receive a fluid to add to the weight of the margin and its means of resistance.

5. Shape. The shape of elytra is various; taken together, in which case, in describing insects, they are denominated coleoptra, their most common form is more or less oblong, or forming more or less a considerable portion of an ellipse; taken separately, it inclines to that of an isosceles triangle, with the exterior side curvilinear: truncated elytra are generally quadrangular, sometimes presenting a trapezium, at others nearly a parallelogram, and at others a square. With regard to their proportions they vary considerably, but the most general law seems to be that the length shall exceed twice the width; in some, as Buprestis grandis, it is more than thrice; in many Staphylinidæ they are as wide as they are long and sometimes wider; they are generally narrower at the apex than at the base, but in some species of Lycus, as L. fasciatus, &c., the reverse takes place; in Telephorus they are nearly of the same width every where: with regard to their surface they are sometimes very convex, as in Moluris; at others very flat, as in Eurychora, Akis, &c.

6. Appendages. These, though not so remarkable as those of the head and prothorax of beetles, ought not to be overlooked. In many Capricorns, as Lamia Tribulus, speculifera, &c., the disk and sides are armed with short sharp spines; in others (Stenocorus, &c.) the sutural and anal angles or one of them terminate in a spine or tooth; sometimes the whole surface, as in Hispa atra, &c., is covered, like a porcupine, with a host of slender spines, or its sides defended by spinose lobes, as in H. erinacea: the humeral prominence is armed with a spine pointing to the head in Macropus longimanus, and forming a right angle with the elytrum in some Curculionidæ, as Rhynchites spinifex; but the most remarkable appendage of this kind is exhibited by Cassida bidens and its affinities,--from the centre of the sutures of the elytrum rise perpendicularly a pair of long, slender, sharp processes internally concave, which both apply exactly to each other, so as together to form a single horn which rises, like a mast from a ship, from the body of the animal[1806]. Besides the appendages here mentioned, the elytra exhibit a variety of tubercles and other elevations of various form and size, which it would be endless to particularize.

7. Sculpture. The sculpture of the organs in question is very various and often very ornamental: but as almost every kind of it will be noticed in the orismological tables, it will not be necessary to enlarge upon it here, especially since I have endeavoured upon a former occasion to explain how it may be useful and important as well as ornamental to the animal[1807]. I shall therefore only notice a few instances, amongst many, in which a particular kind of sculpture distinguishes particular tribes. Amongst those that are Predaceous the Cicindelidæ have elytra without striæ or furrows, while the majority of the subsequent terrestrial tribes of this section are distinguished by them: the Dynastidæ in the Lamellicorn section are remarkable for a single crenated furrow next the suture; in the weevil tribes the numerous species of the genus Apion are ornamented by furrowed elytra with pores in the furrows, which give them the appearance of neat stitching; in many of those beetles that have soft elytra, as the glow-worms (Lampyris), the blister-beetles (Cantharis, Mylabris), and still more in Œdemera, two or three slight ridges generally run longitudinally from the base to the apex, and are visible also on the under-side; as the furrows probably lighten a hard elytrum, these ridges may serve to strengthen a soft one, and it is by these that the first approach is made to the reticular structure of tegmina or the wing-covers of Orthoptera: Lycus palliatus, &c., in its elytra exhibits a direct resemblance of the reticulations of nervures.

8. Clothing. To what I have before said on this subject in general[1808] I shall here add a few remarks, which, though they more properly belong to elytra, may in many cases be extended to the whole body of a beetle. In various instances it happens that the beautiful markings of these organs, as in Macropus longimanus, whose elytra when denuded are black, are produced by short decumbent hairs; in some these variegations are the effect of scales resembling those of Lepidoptera, often of a metallic lustre; from these scales is derived all the brilliancy of the diamond-beetle (Entimus imperialis, Germ.); in some the scales are so minute as to resemble the pollen of flowers, as the white marks observable on the green elytra of the rose-chafer (Cetonia aurata).

9. Colour. The organs of flight in the majority of the Orders with respect to colour are usually the most gaily decorated part of insects; I therefore deferred the notice of that subject till I came to treat of them. In general the colour of insects is either inherent in the substance of their crust, or produced by the hairs or scales that either partially or totally cover it. To confine myself to the Coleoptera, of whose elytra we are treating, it may be observed, I think, in general, that the majority of those that feed upon putrescent substances, the saprophagous tribes of Mr. W. S. MacLeay, are commonly of a more dark and dismal aspect and colour than those which feed upon such as are living and fresh, denominated thalerophagous by the same learned author; this you may see exemplified in his Scarabæidæ and Cetoniadæ. Again, in the Predaceous beetles a similar contrast of colours is often observable. How brilliant and gay are the fierce Cicindelæ! those tigers of insects, as Linné calls them; how black as to colour, how horrible in aspect is their near relation the Manticora: what difference exists in the economy of these animals is not known, except, as I learn from Mr. Burchell, that the latter is subterraneous, whereas the former seek the sunbeam and fly rapidly. I shall now point out a few instances in which the colours of their elytra distinguish tribes or families. Amongst the Predaceous beetles a large family of the Cicindelidæ are distinguished by a middle angular white band, and several white dots on their green or brown elytra, as in C. sylvatica; a family of Brachinus, and the majority of Mylabris, Lamia capensis and fasciatus, &c., by black elytra, with yellow or red bands; Carabus violacea and affinities by the violet margin of these organs; Calliochroma Latreille by their sericeous, and Eumolpus by their metallic, lustre. These instances will be sufficient to turn your attention to this subject, which though not of primary importance in discriminating genera &c., is not without its use in a secondary view.

10. Uses. I must not quit this subject without saying something upon the ends which elytra seem designed to serve. Their first and most obvious use is the protection of the wings when unemployed, that they may not be lacerated or soiled, and rendered unfit for flight in the various retreats to which these animals betake themselves either for food, repose, or to lay their eggs; to promote this purpose more effectually, the wings are usually curiously folded and laid up under them; and where the elytra are very short, as in the Staphylinidæ, these folds are very numerous and complex. In some instances, however, as in Molorchus F., Atractocerus, &c., the wings are only partially protected by the elytra and not folded under them; probably they are less in danger of laceration from their peculiar habits than the generality. Another use is to protect the upper-side of the alitrunk, which for reasons before assigned is usually softer than the under-side, and also of the abdomen, often above nearly membranous, from the injury to which they would otherwise be exposed; in the latter part also the spiracles in Coleoptera are not covered by the inosculations of the segments, as is the case in most other Orders, and therefore probably require some covering when the insect is not flying. In the Apterous beetles this appears to be their principal use; where these organs are connate, or as it were soldered together, the back of the abdomen is a thin membrane; the appearance of two elytra in these cases is given, doubtless, for the sake of symmetry and beauty, a subordinate attention to which may be traced in all the works of creation. If we consider the bulk and weight of many flying beetles, we may imagine that they want some assistance, more than the extent and dimension of their wings seem to promise, to support them in the air, and to enable them to move more readily in it; and although it seems clear from the state of their muscular apparatus that elytra do not move much in flight, yet by giving a broad and concave surface to the air, for then they are usually nearly vertical, they may assist in some measure as sails, and help them in flying traversely and before the wind[1809].

ii. Tegmina[1810]. By this name the learned Illiger has distinguished the upper organs of flight of the Orthoptera and Homopterous Hemiptera[1811]. They may be considered under the same heads nearly as elytra.

1. Substance. Tegmina differ very materially from elytra in their substance, being generally more or less diaphanous, though in Blatta Petiveriana the dark parts are as opaque as elytra, and those of the Mantes that resemble dry leaves are only semidiaphanous. These organs are also of a less dense substance than elytra, something between coriaceous and membranous, which I shall express by the term pergameneous, as somewhat resembling parchment or vellum. Another circumstance relative to this head also distinguishes them,--they are not lined with membrane. In some instances, as in B. Petiveriana just named, they approach nearly to the substance of elytra, and in B. viridis, some Mantes, and Tettigonia, &c., they are little different from wings in their substance; but this does not diminish their right to be considered as tegmina, since their structure is altogether the same.

2. Articulation with the trunk. I observed above that the axis of elytra may be regarded as formed of three parts, one appertaining to each of the areas or their representatives[1812]; in tegmina, and indeed in wings in general, these parts are separate and may be more distinctly traced, the axis of the Costal Area being generally the longest, and that of the Intermediate often the shortest; these axes are suspended in the wing-socket by elastic ligaments, intermixed with hard bony plates, the principal one of which, called by M. Chabrier the humerus[1813], is connected both with the tegmen and the trunk, and in some a little resembles the head and neck of a swan. This structure permits the animal to move the lateral areas in some degree separately, so that each, especially the anal, shall form an angle with the intermediate; as the motion of the latter is not wanted, its axis often falls short of the base, or is obsolete, as in Blatta.

3. Composition. The three areas, traces of which we had discovered in elytra, are particularly visible in tegmina. If you take any cockroach (Blatta), you will at first sight see that in it they are divided into three larger portions by stronger nervures or folds; and if you also take a Mantis, or Locusta Leach, a Fulgora or Tettigonia, the same circumstance will strike you, only you will see that in these the intermediate portion terminates also in an axis; these are what I call the three areas. The external one or Costal is usually the longest and narrowest[1814]; the Intermediate one is commonly triangular, with its inner side curvilinear[1815]; and the interior one, or Anal area, in the Orthoptera is rather oblong; in Fulgora angular, and in Tettigonia it presents an isosceles triangle; with its vertex to the apex of the wing[1816]. The first of these may be defined as that portion of the wing that lies between the costal and postcostal nervures; and perhaps, in some cases, as in Mantis, for there is the fold of the tegmen, the mediastinal may be regarded as its limit; the Intermediate Area is that which lies between the postcostal or mediastinal nervure and the anal fold of the wing; and the Anal Area is the remainder. These areas may perhaps best be made out by tracing each to its axis. To study them carefully in tegmina and hemelytra is of considerable importance; for in them we find the first outline of the general plan upon which the wings of insects are constructed, and which, as we shall see hereafter, more or less enters into the composition of them all.

4. Position, and folding in repose. With regard to their position when not expanded, tegmina vary somewhat in the different tribes. In the Coleoptera we have seen that, except in a few instances, the elytra unite at their suture. Something like this takes place in Fulgora, Cercopis and affinities, in the Homopterous Hemiptera; in these, though the union is not near so exact, yet the tegmina do not lap over each other; they are usually more or less deflexed, with scarcely any portion in a horizontal position: in Tettigonia F., Chermes, Aphis, &c., the middle part only of these organs meets, from which point they diverge both towards their base and apex[1817]. In the Orthoptera the position is quite different, for one tegmen more or less lies over the other. In Blatta, in which the tegmina are nearly horizontal, the left hand one covers almost half the other[1818]: in the other tribes of the Order, with little variation, the Anal Area of the tegmen is horizontal, and covers the back of the animal, and the Intermediate and Costal are vertical and cover its sides; the former, however, in some cases, only forms the angle between them. Sometimes in these the right-hand one is laid upon the left, as in Acheta; and sometimes the reverse of this takes place, as in Acrida K. With regard to the folding of the tegmina, the most remarkable instance that occurs is that of Acheta monstrosa, in which the ends of both these organs and the wings, in repose, are folded like a fan, and then rolled up like a serpent[1819].

5. Shape. The shape of tegmina is various. In the Blattæ and some Mantes they are more or less oblong; in Mantis precaria, strumaria[1820], and others, they incline to elliptical; in Phasma grandis and Acheta monstrosa they are rather panduriform[1821]; in M. gongyloides they are semi-cordate[1822]; in Pterophylla trapeziformis they are rhomboidal[1823]; in Conocephalus erosus they are sinuated; in Locusta Leach they are usually linear or linear-oblong[1824]; in Pterophylla K. they generally terminate in a short mucro[1825]; and in some of those Mantidæ whose tegmina simulate arid leaves, in a recurved one[1826]. In the Homopterous Hemiptera the shape of these organs is less various. In the Fulgorellæ Latr. they incline to a trapezium, sometimes to a pentagon[1827]; in the Tettigoniæ F. they approach to an obtuse-angled triangle; and in others of the tribe they are nearly wedge-shaped[1828].

6. Neuration. The circumstance that most strikingly distinguishes tegmina from elytra is their neuration or veining; which adds much to their strength, without increasing their weight so much as to render them unapt for flight. To look at these organs in Blatta Petiveriana, you would imagine them at first to be deprived of this distinction; but if you observe them attentively, particularly their white spots, you will soon detect their nervures; and if you further examine their lower surface, you will find them very visible. The gibbous Blattæ also, Blatta picta and affinities, the analogues of Erotylus amongst the Coleoptera, have tegmina which, except at their apex, exhibit but faint traces of the nervures of their tribe, and approach to elytra besides by the innumerable minute impressed points that cover them. In the Orthoptera and some Homopterous Hemiptera the nervures may be divided into longitudinal ones more or less ramified, and traversing ones. In the Blattæ the traversing nervures cut the longitudinal ones nearly at right angles, but not at regular intervals, so as to cover the tegmen with quadrangular areolets; in Mantis precaria and affinities the longitudinal nervures of the Anal Area diverge from the base, and are traversed nearly as in Blatta, while those of the Costal diverge from the mediastinal nervure, but the traversing ones form innumerable irregular reticulations; in Mantis sinuata K.[1829] the whole tegmen has such reticulations but less numerous; in Locusta Leach it is regularly reticulated at the base, but the areolets of the apex are quadrangular; in the Mantes, with oblong wings, all are quadrangular; in Pterophylla K. the longitudinal diverging nervures are not numerous, and the traversing ones cut them into quadrangular and triangular areolets, besides which they are covered by innumerable impressed points, so as altogether to exhibit a most exact resemblance of the leaf of some evergreen: in Gryllotalpa the longitudinal nervures of the Anal Area rather converge towards the apex, are traversed by few transverse nervures, and those of the Costal Area which diverge from the mediastinal nervure by still fewer; the neuration of Acheta F. has been before described[1830]; I shall only observe here, that the constructors of stringed instruments of music might, perhaps, from the tegmina of the male, the nervures of which probably modulate the sounds which it produces, take a hint for giving the strings in them a serpentine or convolute direction, and so might produce something new in that department, corresponding with the serpents and French-horns in wind instruments. Of the Homopterous Hemiptera in the Fulgorellæ Latr., which are most analogous to the Orthoptera of all that tribe, the longitudinal nervures are more numerous and branching, more especially toward the apex of the tegmen, and are traversed as much by transverse ones, sometimes reticulating the wing with roundish areolets, as in F. laternaria, and at others with quadrangular ones, as in F. candelaria; in some of these however, as Otiocerus K., Flata F., &c.[1831], there are no traversing nervures; and these lead to the Cercopidæ and others in which the longitudinal nervures become few, and some are without any[1832], and these terminate those of this section of the Order in which the nervures in question are continued to the margin of the wing. We next come to those, Darnis, Centrotus, Membracis, &c., in which they are circumscribed a little within the apex by a traversing nervure, so that the tegmen ends in a margin of pure membrane, and thus some approach seems to be made to the Hemelytra, from Tettigonia, the most conspicuous genus of this tribe, in which the areolets, few in number, like those of Lepidoptera, are not formed, except the terminal ones, by traversing nervures, but by the ramifications of the longitudinal ones; in Chermes the Intermediate Area, which is connected with the base of the wing by a single nervure, is the only part that has any areolets[1833].

7. Colour. Orthopterous insects are seldom remarkable for tegmina of brilliant colours; there is in them none of that gilding or metallic lustre which so often distinguishes elytra: they are also frequently less ornamented in this respect than the wings, with which they usually form an agreeable contrast. Their reticulations and nervures, which are sometimes of a different colour from the rest of the tegmen, decorate them considerably: a remarkable circumstance belonging to this head attends the black tegmina of Blatta Petiveriana; one has four white spots, and the other only three; but as one laps over the other, the symmetry of the arrangement is preserved: the Homopterous Hemiptera are more distinguished in this respect, and some of the Fulgoridæ imitate the Lepidoptera both by their ocelli and spots: Fulgora laternaria, Candelaria, serrata, and Diadema, sufficiently exemplify this remark, as do several Flatæ likewise[1834].

We may observe here--that tegmina are more calculated for flight than elytra, both from their thinner substance, and from the angle that their Anal Area, and often the Costal, forms with the rest of the tegmen; a circumstance which, in wings, M. Chabrier thinks presents some facilities in that kind of motion.

iii. Hemelytra[1835]. The next species of wing-covers, which though varying in the substance of their base, terminate in a part distinct from the three areas, consisting in almost every case of mere membrane, peculiar to the Heteropterous Hemiptera, are called hemelytra, or half-elytra:--this term was also formerly employed, but certainly incorrectly, to denote tegmina. I shall consider them with respect to such of the particulars noticed under the former heads as apply to them, but without repeating them formally.

1. As to their substance, they must be separately considered with regard to their base and apex. In various instances the base, or part consisting of the three areas, is almost corneous, as in Cydnus Morio and bicolor, bugs not uncommon with us, and many others[1836]; in these cases it is lined with a hypoderma like elytra; and in many the points, which are impressed upon it, also perforate the hemelytrum, and seem to act as pores: but in Lygæus, Reduvius, Capsus, Miris, and the majority of the Heteropterous Hemiptera, the organs in question being soft and flexible, may be stated as rather resembling leather than horn;--on this account this part of a hemelytrum is denominated the corium. In Scutellera the portion covered by the scutellum is membranous; and in Acanthia paradoxa, and the cucullated species of Tingis, the wing-covers are entirely so. The apex of these organs is almost universally either membranous or coriaceo-membranous, on which account it is called the membrana. I say almost, because in Aradus and the Hydrocorisæ Latr., this part, though rather thinner than the rest of the Hemelytrum, is also coriaceous; in the latter tribe usually with a very narrow membranous edge; and in many Reduvii and Zeli there is scarcely any difference in the substance of the base and apex.

2. As to the articulation of Hemelytra with the trunk, it seems not strikingly different from that of tegmina: the point or base of the Intermediate Area, which falls short of that of the lateral areas, seems connected by a slender ligamentous piece, with its axis, which is thick; and I do not discern Chabrier's humerus shaped like a swan's head and neck[1837].

3. The composition of these organs differs from that of tegmina in more respects than one: in the first place, they consist, as was lately observed, of four instead of three areas; in the next, they appear to have, at least several of them, a part, which I suspect to be analogous to that above described in Coleoptera, supposed to represent the phialum of wings[1838]. I shall first speak of the areas. In some apterous species related to the bed-bug, Lygæus brevicollis Latr.[1839], &c., there is no trace of the usual areas, and the membrana is a very narrow strip; in L. apterus the former are very faintly traced out, but they are present in all those that are furnished with wings; whence we may conjecture that they are of the same importance in flight with the folds observable in those organs[1840]. The three basal areas may be said most commonly to present three isosceles triangles, the Costal one being narrow and curvilinear[1841], the Intermediate the most ample[1842], and the Anal one the narrowest and shortest[1843], with its vertex towards the apex of the Hemelytrum, while in the two former it is at its base. In Lygæus compressipes (Rhinuchus K. MS.) the Anal Area is cultriform; and in most of the Hydrocorisæ it has an angle in the middle of its posterior margin. The proportion that the membrana or apical area bears to the rest of the wing varies in the different tribes. In some, as before stated, it is obsolete, in others nearly so; in the majority, perhaps, it occupies about a third of the hemelytrum; in Lygæus compressipes, cruciatus, &c., full half; in Alydus calcaratus, two-thirds; in Reduvius, nearly three-quarters[1844]; and in Aradus depressus the corium,--divided, however, though indistinctly, into the three areas,--is driven to the base of the wing: two ends are answered by this structure--as this insect lives under bark, its thin hemelytra take less room; and as it flies, though it has only rudiments of wings, they are more fit to supply their place: the part we are speaking of usually runs obliquely from the vertex of the Anal Area to the base of the Costal.

4. As to their position and folding in repose, Hemelytra are usually nearly or altogether horizontal; but in Notonecta and Plea they are deflexed and cover the sides of the body; and the apical area of one wing precisely covers that of the other; where the scutellum does not intervene, as in Scutellera, Pentatoma, &c., the vertical angles of the Anal Area meet in the middle of the back, so as to exhibit the appearance of a cross. In Notonecta, in which the hemelytra are deflexed, at the apex of the membrana is a fissure which permits the two sides to form an angle with each other, and to apply exactly to the body. In Plea, in which there is no apical area, the posterior margins of the tegmina, as they ought rather to be termed, unite, but do not lap over each other. With regard to the appearance of something like a phialum, if you examine the hemelytra of most species of bugs on the underside, you will see that the costal nervure at the base is inflexed and covers a kind of channel; if you next take one of Belostoma grandis, where the structure is most conspicuous, or even the common Nepa cinerea, you will find in the same situation, adjacent to the inflexed costal nervure, a hollow tube running from the base of the wing, and terminating, after proceeding about one-fourth of its length, in a hollow cavity, which, as it is covered by a membrane, appears to me to be a collapsed pouch. This circumstance is worthy of further and more general investigation.

5. In their shape, with few exceptions, hemelytra more or less represent a wedge, being wider at their apex, where they are usually obliquely truncated, than at the base; but in Plea Leach they are obtusangular, with the angle in the sutural margin; in Notonecta, on the contrary, an obtusangular sinus distinguishes that part; in Naucoris they are curvilinear and every where of equal width; in Ranatra they are linear and straight; in Aradus they are oblong, usually with an external lobe or dilatation at their base: a remarkable instance of the intention of this is observable in a nondescript Brazilian species, in which the head, prothorax, and abdomen, are edged with a number of broad foliaceous appendages; if the base of the hemelytrum had not been furnished with a similar appendage, the symmetry of the whole body would have been destroyed by the hiatus between the prothorax and abdomen, as may be seen by removing the hemelytra; but by this compensating contrivance of Providence, the gap is filled, the above lobe fitting exactly into it.

6. The neuration of these organs will not occupy us long, since the corium or harder part, though in some species there are traces of nervures, is often without them. Those of the cucullated species of Tingis resemble many tegmina in being ornamented by them with a kind of network, which looks like the finest lace; in several Lygæi, Edessa, and some Reduvii, there are a few diverging longitudinal nervures which occasionally by a ramification here and there form an areolet[1845], but there are seldom any traversing nervures. The Apical Area is usually most distinguished by nervures, in some forming several areolets, as in Aradus, in others running parallel to each other, nearly to the end of this area, as in Belostoma grandis, where they are met by a traversing nervure; the object of this is doubtless to strengthen the membrane.

7. Both tegmina and hemelytra are most commonly naked, yet very short hairs are found on those of some species of Cercopis, and in many more instances in those of the latter description, as in Notonecta, several Lygæi and Reduvii, &c.

8. Colours in hemelytra are very various, and in many instances are peculiar to families; in certain Lygæi (L. Hyoscyami, &c.) black and red; in Lygæus compressipes and affinities a dingy black; in some Reduvii black with a large white spot;--but it is needless to enlarge further on this subject.

9. That hemelytra are used in flight is evident not only from the large space allowed for their muscles[1846], but likewise from a circumstance noticed by M. Chabrier, that in flight, in the Pentatomæ Latr., the corium of the hemelytrum is fixed to the wing[1846]; in which case both must describe the same arc.

iv. Wings. We are next to consider organs which are exclusively appropriated to flight, and therefore are properly denominated wings. These in the Orders that have elytra, tegmina, or hemelytra, are the pair that correspond with the secondary wings of the other Orders. It may be said, indeed, that in several instances both tegmina and hemelytra do not differ at all in substance or use from the wings that they cover. This is true; but as their structure in other respects is the same with that of those that are more solid and less apt for flight, it was convenient to consider them under the same name.

1. To begin with the articulation of these organs with the trunk; in general it may be stated that this, as in tegmina and hemelytra, is usually by the intervention of three axes, formed by the conflux of the nervures of the three areas at the base of the wing, which either immediately or by other pieces are implanted in the trunk, so as to receive from it the aërial and other fluids, necessary for its expansion and motions[1847]. Having given this general statement, I shall next apply it to the wings in some of the different Orders. If you carefully extract one from the stag-beetle (Lucanus Cervus) or any large species of the Dynastidæ, in the Coleoptera; the first thing that will strike you, upon examining the base, will be the plate before mentioned called by Chabrier the humerus, which is a stout transverse corneous piece, with a deep sinus towards the wing, filled with ligament: if you again follow the costal, mediastinal, and postcostal nervures, you will find them unite to form an axis, consisting of three parallel pieces, which connects by its intermediate internal piece with one end of this plate. The nervures of the Intermediate Area terminate also in a corneous axis at a greater distance from the base than the other two, which connects with Chabrier's humerus by means of the ligament of the sinus just named. Those of the Anal Area are received by a ligament attached to a transverse plate, widest at its anterior end, which connects with the posterior part of the said humerus; and at its posterior end is united to the postfrænum[1848], with which it forms a right angle. In the Orthoptera Order the structure is not very different, but the axes and other plates of the base of the wing are less distinct and rather cartilaginous; the nervures of the Anal Area often terminate in a transverse one that there forms the segment of a circle[1849]; the inner base of this circle is ligament connected with the postfrænum[1850]. In the Homopterous Hemiptera the three axes may be readily traced, but the humeral plate, with which they all are connected, is more irregular in shape, and in Fulgora longitudinal, with an angular surface; in this Order the nervure, in some cases consisting of cartilaginous rings[1851], in which the frænum and postfrænum terminate in the tegmina and wings, is attached posteriorly to the ligament of the Anal Area. In the Heteropterous section the three axes are evident, but the humeral plate is not easily made out. In the Libellulina the axes of the Costal and Intermediate Areas are the coloured broad plates at their base, formed by the dilatation of their nervures; that, however, of the Anal is not dilated, but forms one nervure, in the primary wing, with the frænum, and in the secondary with the postfrænum. Having given you this clue to trace the axes in those tribes in which they are most conspicuous, it will assist you in searching for them in the remaining Orders, in all of which they may be traced, except perhaps in those minute Hymenoptera whose wings have solely the costal nervures; probably in these there is only one axis. In the Lepidoptera and Hymenoptera a circumstance connected with the present head is observable, which is not to be discovered in the other Orders: these are the tegulæ or base-covers, which appear intended to defend the base of the anterior wings. They are concavo-convex scales, which in the Lepidoptera are large and of an irregular shape[1852], but in the Hymenoptera are smaller and semicircular[1853].

2. Wings, with regard to their substance, may generally be termed membranous; but they vary in this respect, some being much thicker than others, either partially or totally: in spotted wings, as in those of many Libellulina, Tettigoniæ F., &c., the dark opaque parts are denser than those that are transparent: in several Orthopterous insects, as in Phasma, some Mantes, &c., the Costal Area or covering part of the wing is of a substance equally firm with that of the tegmen. This is a compensating contrivance, that where the latter is shorter and smaller than the former, its membranous part, when folded, may be protected from injury. Another similar contrivance of DIVINE WISDOM is exhibited by those Pterophyllæ K. (Locusta F.) whose tegmina resemble the leaves of plants (Pt. laurifolia, &c.); in these the tip of the wings when folded being longer, is not covered by the tegmina, and therefore exposed to injury; to prevent which this small piece, while the whole wing, as far as covered by those organs, is membranous, is of the same substance with them[1854]. The wings of most Coleoptera, Orthoptera, Hemiptera, and Thereva coleoptrata, in the Diptera, &c., are of a firmer substance than those of the other Orders; in many Locustæ Leach, Fulgoræ, &c., they are nearly as firm as the tegmina; and in Ascalaphus italicus, except at their base, the secondary wings are less membranous than the primary. M. Chabrier has observed[1855] that the wings of insects in general diminish in thickness from their base to their apex, and from their anterior to their posterior margin.

3. I should have had, it is probable, but little original matter to communicate under the head of the composition and neuration of wings, had M. Jurine, who has written so ably on those of Hymenoptera, undertaken a survey of the organs of flight in every Order of insects: but as his views were confined to only two of the Linnean Orders, it is not wonderful that his system and set of terms should fail where a generalization is necessary; and I may stand acquitted of presumption and conceit if I attempt to substitute a system and body of terms more universally applicable. Had the plan of this able Entomologist led him to pay attention to tegmina and hemelytra, their division into three longitudinal areas would have immediately struck him; and having acquired this outline of the greater natural divisions, he would have applied it to the Orders that have wings only, and having discovered that it is to be traced in all, the result would have probably superseded my labors. Had his life been longer spared, perhaps something of this kind would have been effected by him; but as he, alas! is gone, and no abler hand seems to have undertaken the task, I will do what I can to give you satisfaction on this subject[1856]. You have already got a tolerably good idea of these areas from what has been said upon the subject under tegmina and hemelytra; but I shall now more particularly state to you how they are circumstanced in wings. I shall first explain the general law as to their limits. The Costal Area[1857] is all that longitudinal portion of the wing that lies between the anterior margin and the postcostal nervure; the Intermediate Area[1858] is all that longitudinal portion of the wing that lies between the postcostal and the anal nervures; and the Anal Area[1859] is all that longitudinal portion of the wing that lies between the anal nervure and the posterior margin. But there are other helps to enable you to distinguish the areas in the different Orders. The Anal Area in all Orders forms the posterior fold of the wing; in Coleoptera turned under when in repose; in Orthoptera folded like a fan; in Lepidoptera, in some Papilionidæ, forming an arch over the abdomen. Again, in Blatta, the Costal Area is distinguished chiefly by longitudinal nervures; the Intermediate by oblique ones; and the Anal by radiating ones; and in both this tribe and the Mantidæ this last Area is marked out from the Intermediate by a marginal notch, which is not present in Phasma, but is found in both sections of the Hemiptera. In Locusta Leach the notch is between the Costal and Intermediate Areas: in Phasma the nervures of the Intermediate Area are branches of the externo-medial, while those of the Anal, as they do in all the Orthoptera, diverge from the base of the wing: in many, as in Pterophylla K., the part of the wing lately alluded to, that is longer than the tegmen, and of the same substance, points out the limit of the Costal Area; and in others this part terminates in a segment of a circle and is differently reticulated at the apex from the Intermediate: in the Homopterous Hemiptera and the Libellulina, in which the areas at first seem indistinct, they may generally be easily traced by following them from the axes. The separation of the Costal from the Intermediate in the remaining Orders seems less easy on account of the branching of the nervures: in the rest of the Neuroptera and the Lepidoptera, if the posterior branches of the postcostal nervure are not included, you will have a narrow Postcostal Area, which in most cases forms an angle more or less prominent, in Corydalis almost a right angle, with the Intermediate: in Hemerobius and affinities this part is distinguished by areolets formed by transverse nervures, while those of the rest of the wing are longitudinal[1860]: but if the posterior branches are included, the Costal Area will be more ample: a similar observation applies to the Hymenoptera and Diptera; in these, in all cases, the areolets adjoining the anterior margin, which follow the stigma, should be regarded as belonging to the Area in question[1861]. In those tribes of the former Order, whose wings are without nervures, the areas are often marked by folds.

M. Chabrier has observed that in Coleoptera the specific weight of the margin of the wing, and its means of resistance, are augmented by a liquid which is introduced, at the will of the animal, into a long pocket under the brachial, here called the costal and mediastinal nervures, covered by a supple membrane, which in a state of repose becomes flaccid[1862]: it is easily detected, being of a paler colour than the nervures between which it lies; this is what I call the Phialum; we have before seen that it exists also in Elytra and some Hemelytra[1863]; but I have not detected it in any other wings.

I have before given you a sufficiently full account of the alulæ or winglets of Diptera[1864]; and shall here only observe that they are not confined to one particular tribe, as has been usually imagined; but though sometimes extremely minute, simple, and not easily detected, are an universal distinction of the Order.

Having thus endeavoured to elucidate the larger Areas into which wings appear to be divided; I shall next say something on the smaller ones produced by the intersection or ramification of the nervures; these had been named areolets (areolæ) several years before M. Jurine's work, in which he calls them, I think improperly, cellules (cellulæ), was published; I therefore retain the prior term. The general structure of the nervures of the wings of insects having been before explained[1865], I shall not here repeat what I then said; but there is a curious circumstance connected with it, particularly visible in the wings of certain Hymenoptera, that I must not pass without notice. If you examine attentively with a microscope against the light the wing of any Nomada or Andrena, you will discover little transparent points in some of the smaller transverse nervures that form the middle areolets, in which the nervure becomes white and looks as if it was interrupted, though in substance it seems continued: these little points, somewhat resembling minute air bubbles detained in the tubes, are what M. Jurine, who first discovered them, has, on that account, named bullæ, which he thus further describes:--"When the tube (of the nervure) arrives at the spot where a bulla is to be formed, it extends itself on all sides in minute threads in the upper membrane of the wing, losing its colour and tubular structure, which it resumes immediately after the formation of the bulla[1866]." But if you look closely at them you will find that there is always a slight fold of the wing that cuts the nervure exactly at the bullæ, and if the fold changes its direction they accompany it; their object, therefore, is clearly to relax the tension so as to admit a little motion where the fold is; consequently, rather than bullæ (bubbles), they should be denominated articulations. A similar construction, but on a larger scale, may be observed in the wings of Coleoptera[1867] and some others, as Psocus, where the folds traverse the nervures. I shall next make a few observations on the principal nervures; and first a word upon their names. M. Jurine, being of opinion that a striking analogy exists between the wings of insects and those of birds, in which M. Chabrier seems to agree with him, has named the nervures in the anterior margin of the wings of the former, radius and cubitus, as corresponding with the bones so named in the fore-arm of the latter, and the plate which often terminates these nervures in Hymenoptera, he names the carpus; it may look like presumption to differ from two such weighty authorities, but as their observations seem to have been too limited, in one case to the Hymenoptera and Diptera only; and in various Orders there is nothing analogous to the stigma or carpus, and all the other nervures of an insect's wing have no analogue in that of a bird, but more especially as M. Latreille seems to think with me on this subject[1868], I have retained Linné's term for the marginal nervure, and for most of the others have adopted those of the great French Entomologist just mentioned. I shall here only further observe,--and it seems to me an observation of prime importance, in the determination of the question of the analogy of the wings of insects,--that they are not, as in birds, the fore-leg converted into an organ of flight, but, like the wing of the Draco, an organ superadded to the legs; and, further, that the connection is not with the fore-legs, but, as has been before observed[1869], with the two posterior pairs.

The Costa[1870] is usually the strongest of the nervures, and that upon which the wing seems to be built; but in some cases, as in Blatta, Scutellera, Cynips, &c., it is represented by the mere membrane of the anterior margin; in some Coleoptera, as in Geotrupes, Dytiscus, &c., its structure, except at the base, appears to be annular or nearly so, at least a vast number of corrugations, running transversely, are observable on its upper and lower surfaces; it is thus capable of greater tension and relaxation, and more flexile. The stigma or carpus[1871], though most conspicuous in the Hymenoptera Order, may be traced in some Coleoptera, Heteropterous Hemiptera, the Libellulina, &c.; but it has no representative in the Orthoptera, Lepidoptera, Trichoptera, &c. The mediastinal is usually a very slender nervure, placed between the costa and postcosta, sometimes terminating in the former[1872], and at others in the latter[1873]: in the Orthoptera, Lepidoptera, &c., however, and some others, it is a very conspicuous and principal one[1873]; in the Hymenoptera it is obsolete, merging in those nervures[1874]. The Postcosta is the principal nervure of the wing in Scutellera, but in Staphylinus it is wanting; in Chalcis sispes it is the only true nervure of that organ, the others being represented by spurious ones[1875]. The externomedial and internomedial are sometimes distinct at their origin, but more frequently are branches from a common stem.

Having made these general remarks, I shall now consider particularly the neuration of the wings in the different Orders, beginning with the Coleoptera. The first thing that strikes the physiologist in surveying a wing belonging to an insect of this Order, is the general arrangement of the nervures[1876]; which are so placed that the required degree of tension may be given to every part of this organ: thus some are nearly straight[1877]; others run in a serpentine direction[1878]; others are forked with one branch recurrent and another proceeding onwards[1879]; others again are insulated, or do not originate from the base of the wing, or from other nervures, but are merely placed to strengthen an open space of it[1880]: these nervures are also usually broader and more substantial than those of the wings of the subsequent Orders. Another striking circumstance with regard to them is that the nervures form few or no closed areolets, except in the Costal Area, where they are inconspicuous; in Dytiscus marginalis, indeed, and Tenebrio Molitor one or two may be found, but in general there are none. In many of this tribe the postcosta, which terminates at the joint of the wing, becomes recurrent, so as to form a hook, which perhaps represents the stigma, as in Dynastes[1881]; in Creophilus K., a rove-beetle, there is no hook but a broad plate adjacent to the costa. In the Strepsiptera Order the neuration is extremely simple, the nervures, except one insulated one, diverging from the base of the wing[1882]: in this respect, as well as in the form of that organ, an approach is made to the Orthoptera. In the Dermaptera this approach is still more evident; in the common earwig[1883], the diverging nervures become numerous; between each is an insulated one, taking its origin in the middle of the wing, and running to the margin; a little nearer to the latter all the nervures are dilated into a plate; those of the anal area are angular[1884], and the exposed part of the costal is as hard as the elytra. The neuration in the Orthoptera Order may be called radiate, the longitudinal nervures for the most part diverging from the base of the wing like rays: in some few instances[1885], but not often, I believe, an insulated nervure intervenes between each; traversing or connecting nervures, cutting the longitudinal ones in various directions, ornament these wings with an infinity of areolets, causing them to resemble fine gauze or beautiful lace or net-work; very often these areolets are quadrangular, sometimes rhomboidal, frequently nearly circular, and differing occasionally, as has been before observed[1886], in the different areas: it sometimes occurs that there are no traversing nervures[1887], when the wing of course is without areolets. In the Heteropterous Hemiptera the type of neuration, as to the wing, seems borrowed from the Coleoptera, a further proof that these are the analogues of that Order amongst the Haustellata Clairv. In these the nervures usually are few and dispersed, and seldom form any closed areolets. If you examine any Scutellera, Pentatoma, or Lygæus, you may trace the uncinated, forked, serpentine, and insulated nervures of Coleopterous insects; in Gerris and Velia there is an approach to the neuration of some Homopterous species, and in Belostoma &c. the wing is reticulated by spurious nervures. In the Homopterous section there are several types of neuration; thus the Fulgoræ resemble the Orthoptera in this respect; while the Tettigoniæ F., &c., approach nearer to the Hymenoptera and Diptera, and have their apical areolets circumscribed within the margin by a traversing nervure; in Flata, &c., the areolets are mostly formed, not by traversing nervures, but by the branching of the longitudinal ones; in this respect they are not unlike the Lepidoptera. In this last-named Order there are some variations with regard to their neuration--thus, amongst the butterflies in Urania, &c., there is no closed areolet in any of the wings, and almost all the nervures diverge from the base[1888]; in Morpho, &c., there is only one in the primary wing[1889]; in Heliconia, &c., there is one in both wings; amongst the moths, in the Bombyces L., this is divided into two, and in Cossus labyrinthicus Don. into three areolets: in some butterflies (Lycæna) there is one insulated nervure[1890], and in others (Hesperia) there are two[1891]; in these two last, and Heliconia, Urania, &c., the end of the Costal Area is divided into several areolets by oblique nervures[1892], which gives them some analogy to the wings of many Neuroptera; and at the base of this Area, in Morpho, is a roundish areolet[1893]. In this Order the externo-medial and interno-medial nervures coalesce into one, and are only represented separately by their first and third branches[1894]. In the Neuroptera Order the general type of neuration is borrowed from the Orthoptera; but in Osmylus, Termes, &c., there is an approach to that of Flata in the Homopterous Hemiptera, and in Psocus to others of that section; in the second of these genera the nervures, except those of the costal margin, are spurious.

I now come to the Order in which M. Jurine has laboured with so much success, I mean the Hymenoptera; and I only regret that his labours were directed to so small a portion of the Class Insecta, and in that portion only to a part of the upper wing; I say only a part, because all those areolets of the posterior part of the wing, in some cases amounting to five[1895], that lie behind his cubital cellules, are not employed by him as diagnostics, and are left without a name. By dividing the areolets of the Intermediate Area of these wings into three portions, the basal, medial, and apical[1896], I have endeavoured to remedy this defect, and by naming each set of areolets in the middle portion, as you will see in the Orismological Definitions, under the term Areolets, you will find it easy to describe any given areolet and its place in the wing; those of the base may be called the anterior, intermediate, and posterior, where three occur; and the first and last of these terms will suffice where there are only two; the apical areolets, or those that are open to the margin, may be called, first, second, and third in the order of their occurrence, reckoning from the anterior or costal margin.

In this Order it is curious to trace the progress of neuration in the wings of different genera. Thus in Psilus only the costal nervure and the stigma are to be traced[1897]; in Chalcis the postcostal and stigma[1898]; in Codrus and Leucospis the costal, postcostal, stigma, and a nervure representing the externo-medial and interno-medial coalescing into one[1899]; in Omalus the basilar areolets appear[1900]; in Crabro both basilar and medial[1901]; in Cynips basilar, medial, and apical[1902]; and in Hylotoma the wing is filled with its greatest complement of areolets[1903]. The medial areolets of the Intermediate Area, as you will see in the definitions, form three distinct series; these may be called the protomesal, deuteromesal, and tritomesal, reckoning from the postcostal areolets; the first of these corresponds with the cubital cellules of Jurine. These series may be expressed, according to the number of their areolets; by figures, the protomesal standing first. They vary much in this respect in the different genera. Thus in Cyclostoma K.[1904], reckoning the didymous areolet as two, the numbers will stand 4:2:1; in Hylotoma, &c., 3:2:1[1905]; in Aulacus, &c., 2:2:1[1906]; in Bracon, &c., 2:1:1[1907]; in Chelonus, 2:0:1[1908]; in Cynips erythrocephalus Jur., 2:0:0[1909]; in Formica, 1:1:1[1910]; in Oxybelus, 1:0:1[1911]; in Chrysis, 0:1:1[1912]; and in Cynips Rubi K., 1:0:0[1913]. The most natural number is 3:2:1. The next in importance to the medial areolets of the Intermediate Area are the apical, or those open to the margin; the most usual number of them, excluding the postcostal areolets which belong to the Costal Area, is three; but in Sirex there is an approach to four[1914]; in Evania there are only two[1915]; and in Philanthus there are none[1916]; in many, as Prosopis, Nomada, Andrena[1917], though there is the usual number, they are incomplete and do not reach the margin. The basal areas are of little importance in assisting to determine genera; they are most commonly two in number, but in Cynips, &c., there is only one[1918]. The shape and other circumstances of the areolets vary considerably in different genera and species: upon these however I shall not enlarge further, but proceed in the next place to consider very briefly the wings of the Diptera Order as to their neuration. These are not so easily made subservient to a general plan. The basilar areolets are now reduced considerably in length, occupying merely the base of the wing[1919]; the medial are become less numerous and important[1920]; and the apical, in a variety of instances, are the most conspicuous[1921]; in some wings, as in those of Penthetria, the Intermediate Area has no nervures or areolets, or only spurious ones; in Psychoda the nervures diverge from the base almost without branching, so as to form no closed areolets[1922]; in many, the lower medial areolets are very long, resembling the basilar in Hymenoptera[1923]; these are often crowned by a single small one, as in the Stratyomidæ, Tipula, &c., from which numerous branches proceed to the margin[1924]; but in Musca two large ones approach the margin, the anterior one having an angle open to it[1925]; in the Hippoboscidæ almost the whole of the wing is occupied by the apical areolets[1926]; though in some cases they are incomplete[1927].

4. I am next to consider the position of wings in repose and their folding. The most important object of this is that when unemployed they may occupy less space, be less in the way of the insect, and be most effectually protected from injury. Another end is also served by this structure,--that wings can thus be very ample, and present a large surface to the action of the atmosphere without incommoding the insect when it has not occasion to use them.

With respect to this head, insects may be divided into two classes--namely, those whose wings in repose are covered by wing-cases harder than the wings themselves, and those that have no such protection. In the former the wings, though the rule admits several exceptions, have more folds than in the latter. As the different mode of folding the wings has been assumed for a characteristic of the earlier Orders, I shall explain to you with as much brevity as possible how each is circumstanced in this respect, beginning as usual with the Coleoptera.

There are two principal folds of the wing in this Order, which may be named the anal and the apical: the former is when the Anal Area or part of it is folded on the under surface of the base of the wing; this fold is always more or less longitudinal: the latter, the apical fold, is by means of the commissura or joint of the postcosta lately mentioned: which in Hister, Staphylinus, &c., for obvious reasons[1928] is nearer the base of the wing; in Necrophorus in the middle; in Dynastes Aloeus beyond the middle[1929]; in Tenebrio Molitor near the apex; and in Dytiscus marginalis there appears to be no joint at all; but the fact is, that in this insect the postcosta,--the termination of which really forms the joint, the costa itself being only flexible at that point,--stands at a greater distance from the latter at its end. Well, at this joint the above fold is made, the apex of the wing, being first folded longitudinally, turning under and inwards, and forming an angle, more or less acute, with the joint or costal margin, so that the fold is not quite but nearly transverse: this at least is the case in Geotrupes stercorarius and other Lamellicorns: in Staphylinus, &c., there are several transverse and longitudinal folds, and thus the wing is more easily packed under the short elytra; in Molorchus, Necydalis, &c., in which it is left uncovered, except at its base, the anal fold takes place, and the apical in some degree; a short portion near the apex forming an obtuse angle with the margin; in Atractocerus the wing appears to be only longitudinally folded; and in Buprestis vittata only the anal fold is to be detected. Besides these transverse and longitudinal folds these organs, in many beetles, have an infinity of fine corrugations, which ramify like the nervures of the tegmina of Flata[1930], &c., proceeding from the Costal Area or the disk of the wing to the posterior margin; the object of these plicatures is doubtless to present a more ample surface to the action of the atmosphere in flight[1931]. When all these folds have been made in a Coleopterous wing, the apex of the one at its posterior margin crosses or rests upon that of the other[1932].

In the Dermaptera[1933], at least the common earwig, there is a triple transverse fold of the wing, and besides this it has numerous longitudinal ones like those of a fan, each of the diverging nervures representing one of the sticks. In the Strepsiptera the folds are only longitudinal; a circumstance which, besides the form and neuration of the wing, sufficiently attests that its station is more near the Orthoptera and Coleoptera than the Diptera. We next come to the Orthoptera[1934]; in these the folds in general are longitudinal; and those of the Anal Area in particular, either in whole or in part, exact counterparts of a fan: wherever there is a straight nervure, there is usually a fold or a tendency to it; this is the case even with the short oblique ones observable in the Intermediate Area of Blatta: in this tribe the Anal Area, or a considerable portion of it, is folded under the rest of the wing, and the whole lies on the back of the animal, so that in this wing there are only two primary folds; but in those with a narrower body, as Phasma, &c., there are more, and the Anal Area, folded like a fan, lies horizontally on the back; the Costal is vertically applied to the sides, and the Intermediate is between both, as in the tegmina[1935]. In Gryllus Latr., Gryllotalpa, &c., when the wings are folded, the end of the Anal Area projects so as to present the appearance of two tails[1936]; and in that remarkable Chinese animal Gryllus monstrosus, in which these tails are very long, they are convolute like those of some quadrupeds[1937]. It is to be observed that in the secondary folds of these wings the angles of the folds are surmounted by a nervure.

In both sections of the Hemiptera Order, as in the Coleoptera, the Anal Area is turned under the wing and lies over the back of the insect; this is the only primary fold, but besides there are several longitudinal semifolds or secondary ones, in which one part of the surface forms an obtuse angle with another; and in Tettigonia, &c., these folds ramify in the wings as well as in the tegmina at the margin: a number of semifolds also, sometimes transverse and sometimes oblique, run in pairs from each side of every nervure of the disk of both tegmina and wings in the genus last named, the use of which has been before mentioned[1938].

We now come to those Orders that have four membranous wings: first, I shall consider the Lepidoptera. With respect to the position of their wings in repose some variations take place. In the majority of the day-fliers (Papilio L.), when the animal reposes the wings are applied to each other by their upper surface so as to be vertical; but in the skippers (Hesperia), the secondary wings assume a horizontal position, while the primary are vertical but applied to each other. In the Crepuscular tribes (Sphinx L.) the upper wings are incumbent on the lower, and deflexed. In the night-fliers (Phalæna L.) the types of position are various. In some Attacus, Saturnia, Noctua, &c., the wings cover each other, and are a little inclined from a horizontal position; in Gastropacha, Odenesis, and some other Bombycidæ, they are deflexed, and the anterior margin of the under wing projects beyond that of the upper: in some of the Tineæ L., as Crambus, the wings are convoluted, and in others, Galleria, they are applied close to the sides of the body, and being elevated at the apex, terminate, to use a French term--en queue de coq: in Noctua, Geometra, &c., the wings usually cover the abdomen, and are nearly horizontal. With regard to the folds of their wings, the Anal Area of the secondary is the only part that has any striking one; in Papilio Hector and affinities it turns up so as to defend the sides and part of the back of the abdomen; in Morpho Teucer it turns down, and meeting that of the opposite wing, forms a semitube which receives and shelters that part below. In the Crepuscular and Nocturnal Lepidoptera this fold, especially in the former, is very slight. With respect to semifolds in the Diurnal, there is one originating in the disk, between each of the nervures, that goes to the margin of the wing; likewise the under wings, particularly of many Noctuæ, Arctiæ, &c., have many longitudinal semifolds.

In the Neuroptera Order several variations take place with regard to the position of these organs in repose: thus, in Æshna, Libellula, &c., they continue expanded; in Argion they are applied to the body; in Myrmeleon the upper are horizontally incumbent on the lower; in Hemerobius they incline to the horizon. With regard to their folds in Æshna, &c., the longitudinal nervures alternately form the summit or the bottom of a semifold, as do those branches that terminate in the posterior margin; this kind of plicature may be observed, but in a less degree, in Ascalaphus, Myrmeleon, &c.; in Panorpa every nervure is the ridge of a slight fold; in Termes, on the contrary, it forms its bottom. In the Trichoptera, the under wing being much more ample than the upper, the Anal Area forms a fold under the wing, and there seem longitudinal secondary folds besides.

We now come to the Hymenoptera. In this Order the wings, as to their position in repose, are usually incumbent upon each other, and cover the abdomen; in the Vespidæ, however, they are placed parallel to the body, but do not cover it. Before I notice the plicature of these wings, I must recall your attention to what I lately observed[1939] with regard to Jurine's bullæ (bubbles), but which are really the joints of the nervures, as they are to be found only where the folds pass; and where they exist they are an index by which the folds, or rather semifolds, may be traced. I counted eleven of these little joints in the upper wing of Andrena cineraria; sometimes, however, instead of a bulla, a nervure stops short to admit the fold. Wings in this Order have often three longitudinal semifolds more or less conspicuous; these you may trace in the saw-flies (Tenthredo L.), whose wings Linné terms tumidæ, by which term he would indicate the elevation of the whole surface produced by this structure; in the under wings of these, and Scolia, Bembex, &c., the Anal Area is turned under the wing, as in many preceding tribes[1940]: in Sirex, &c., that Area of the upper wing turns upwards, forming an acute angle with the rest of the organ; the same circumstance distinguishes the under wing in the Ichneumonidæ. Several apical semifolds, marked by a pellucid streak, distinguish Tiphia F., and in Bombus, Bembex, &c., an infinity of branching ones, like those before described in Coleoptera, corrugate the apical margin. In the Vespidæ the upper wings are folded longitudinally into three nearly equal portions, but in the under ones the Anal Area only forms the fold.

In the Diptera Order, as to their position when at rest, the wings are mostly incumbent one on the other; but in Psychoda they are deflexed, so as to form a kind of penthouse. With regard to their plication, in some, Tipula oleracea, &c., a slight oblique semifold runs from the stigma to the apical margin, and the Anal Area has two, as it has in many Muscidæ, itself forming nearly a right angle with the rest of the wing; besides these it is corrugated with minute transverse semifolds, which are observable also in several other Dipterous insects; in many Stratyomidæ they are oblique, and run from the disk to the posterior margin; and in Asilus, Bombylius, &c., they are wavy.

5. We are next to say something upon the shape of wings: this, though apparently extremely various in the different Orders and tribes, may I think be traced in every wing to one original prototype, a triangle with the largest angle rounded and subtended by the anterior or costal margin: in some, as the Coleoptera, Orthoptera, &c., this type of formation is a right-angled triangle[1941]; and in others, as in the Hymenoptera, Diptera, &c., the majority of the Neuroptera, &c., it is an obtusangled one[1942]; it may be further observed, that in receding from these forms wings very often assume that of the half or quadrant of some regular figure, as we shall see when we consider those of the different Orders. Another general observation I shall first mention,--that these organs are universally narrowest at their base and widest at the apex, provided we consider as the apex the termination outwards of the three Areas; otherwise we might say that wings in the Coleoptera, Orthoptera, &c., were wider at the base than at the apex[1943]. The wings in the former Order, and in several of the Heteropterous Hemiptera, as Gerris, Velia, &c., may in general, as to their shape, be termed semicordate or semiovate[1944]; in the Dermaptera they incline to an oval figure[1945]: in the Strepsiptera, Orthoptera, most Homopterous and many Heteropterous Hemiptera, they approach to the quadrant of a circle; in a considerable portion of the Lepidoptera the two under wings, if united at their posterior margin, approach a circular form; the upper ones vary a little from the prototype of the under ones, forming an obtusangled triangle[1946]; in many Neuroptera the primary wings may be called oblong or linear-oblong, while the secondary betray more evidently the right-angled or obtusangled triangle; in the Hymenoptera this latter form is every where conspicuous, with little deviation, except in the rounding of the angles[1947]; and, finally, in the Diptera this form shades off again into an oblong, ovate, or linear shape, the wing being most commonly attenuated at the base into a kind of footstalk[1948]. Some singular variations with respect to the termination or marginal processes of the wings are exhibited by many Lepidoptera; thus in Attacus Atlas, &c., the primary wings are falcated or hooked at their apex[1949]; and in great numbers both wings are there scolloped into alternate bays and capes, if I may so speak, varying in depth and length[1950]. There is usually a sinus between every pair of nervures, each of which terminates in the adjoining prominence, as a fold does in the sinus[1951]. Where present, in the primary wings there are eight of these sinuses, and in the secondary, where they are most usual, seven; some are remarkable for the long tails which distinguish their secondary wings; those in Papilio are usually an elongation of the fifth, from the anterior margin, of the prominences before mentioned, into a spathula-shaped diverging process, varying in length and width[1952]: but in P. Ulysses it does not diverge; and in P. Podalirius it is linear. They are found also in other subgenera; thus in Urania Patroclus there are two; in U. Riphæus three; in Erycina Cupido five; and in E. Endymion six of these tails; in some, as in E. Dorylas, the whole wing seems to form the tail; in others again, as in Hesperia Proteus and Bombyx Luna, it is an elongation of the anal angle. Other wings in this Order are divided into lobes resembling feathers, as you may see in Pterophorus hexadactylus, &c.[1953]

6. We are next to consider the clothing of wings: these, in the Orders in which they are covered by elytra, tegmina, or hemelytra, are generally naked, except that the spots in those of Fulgora laternaria, serrata, &c., and the whole wing in Flata, Aleyrodes, and others, are covered with a kind of farinaceous powder; but in all the remaining Orders, hairs or scales are more or less implanted in these organs: as the Lepidoptera are the most remarkable for the clothing of their wings, I shall leave them till the last, and begin with the Neuroptera. If you lightly pass your finger over the wing of any dragon-fly (Libellula F., Æshna F.), from the apex towards the base, you will find that the longitudinal nervures are, as it were, serrulated with very minute bristles, which point towards the extremity; if you next move the finger across the wing, from the posterior to the anterior margin, a similar circumstance will strike you. M. Chabrier conjectures that, amongst other uses[1954], these hairs may contribute to fix the atmospheric fluid when the wings are depressed in flight, while it glides over them as they rise[1955]; in Ascalaphus, Myrmeleon, Nemoptera, Hemerobius, &c., the nervures are more visibly bristled; the bristles diverging on each side from the longitudinal ones, but all pointing towards the apex from the connecting or transverse ones; in Panorpa, besides these bristles, short hairs, pointing the same way, are thickly planted in the membrane of the wing; and in Hemerobius the margins of the wing are fringed; in the Ephemerina, Corydalis, &c., the wings are naked. In the Trichoptera Order, as their name imports, they are covered with minute decumbent hairs, less easily seen but still existing in the secondary pair. In the Hymenoptera in general the wings are covered with minute hairs or bristles; but in Tiphia, Scolia--with the exception of S. Radula and affinities in which they are hairy--and others, the wings are nearly naked; in Pompilus, Pepsis, &c., the hairs are infinitely numerous and very short; in the Sphecidæ, Mutilla, &c., they are more distinct, longer, and less numerous; in the humble-bee (Bombus) and many others the apex of the wing is darkened by a large number of more conspicuous hairs, each of which seems to spring from a minute tubercle: as these tubercles are in a part of the wing that is strengthened by few nervures, they may probably be intended to supply their place, in giving firmness and tension to this part. The wings of Diptera, under the present head, may be viewed with regard to the hairs that are implanted in the membrane of the wing, in its nervures, and in its margin. In the first view, in Stratyomis and immediate affinities the wing is nearly naked; but in Xylophagus, Beris, and the great majority of the Order, the membrane of the wings is thickly planted with innumerable very minute bristles, not to be seen but under a powerful lens, often black, and seemingly crowning a little prominence, and giving the wing an appearance of the finest net-work. As to the clothing of the nervures, the costal, in Anthrax, Bombylius, &c., is often remarkably bristly at the base, with hairs intermixed; in Œstrus Ovis, in the inner margin or edge of this nervure, is a single series of bristles, or rather short spines, like so many black points; in Œ. Equi the whole costa is covered with short decumbent hairs or bristles; in Musca pagana F., just at the apex of the costal areolet, that nervure is armed with a spur or diverging bristle larger than the rest, which is also to be found in many others of the Muscidæ, some of which have two and others more of these spurs. The little moth-like midges (Psychoda Latr., Hirtæa F.) at first appear to have the whole surface of their wings covered with hairs; but upon a closer examination it will be seen that they are planted in the nervures, from each of which they diverge, so as under a lens to give it a very elegant appearance[1956]. This fly has its wings beautifully fringed with fine hairs, the third circumstance to be attended to under this head; in the Tipulidans, and many others of this Order, the apex and posterior margin are also finely fringed with short hairs. Some Dipterous insects make a near approach to the Lepidoptera in the covering of their wings: in the common gnat, when the wings are not rubbed, the nervures are adorned by a double series of scales, and the marginal fringe also consists of them[1957]; and in a Georgian genus, which appears in some degree to connect Culex with Anthrax &c., there are scales scattered upon the membrane as well as upon the nervures; besides, its antennæ[1958] and abdomen are also covered with them.

The Order, the clothing of whose organs of flight excites the admiration of the most incurious beholder, is that to which the excursive butterfly belongs, the Lepidoptera. The gorgeous wings of these universal favourites, as well as those of the hawk-moths and moths, owe all their beauty, not to the substance of which they are composed, but to an infinite number of little plumes or scales so thickly planted in their upper and under surface, as in the great majority entirely to conceal that substance. Whether these are really most analogous to plumes or scales has been thought doubtful. De Geer is inclined to think, from their terminating at their lower end in little quills and other circumstances, that they resemble feathers as much as scales[1959]; Reaumur on the contrary suspects that they come nearer to scales[1960]. Their substance, approaching to membrane, seems to make further for the former opinion, and their shape and the indentations that often occur in their extremity, furnish an additional argument for the latter. Their numbers are infinite; Leeuwenhoek found more than 400,000 on the wings of the silk-worm moth (Bombyx Mori)[1961]; and in those of some of the larger moths and butterflies the number must greatly exceed this. You will observe however that in many Lepidoptera the wings are partially, and in some instances generally, transparent: thus in Hesperia Proteus, a butterfly before noticed for the long tail that distinguishes its secondary wings, there are many transparent spots; in Attacus Atlas, one of the largest of moths, and its affinities, there is as it were a window in each wing formed by a transparent triangular space; in A. Polyphemus, Paphia, &c., the pupil of the ocellus is transparent, which in the former is divided by a nervure. In several of the Heliconian butterflies, and in Zygæna F., &c., the greater part of both wings is transparent, with scales only upon their nervures, round their margin, or forming certain bands or spots upon them; in Parnassius Apollo, Mnemosyne, &c., the scales are so arranged as not wholly to cover the wings, which renders them semidiaphanous; and in some (Nudaria) the wings are intirely denuded. With regard to size, the scales vary often considerably in different tribes; in Heliconia they appear to be more minute than in the rest; and in Castnia they are the largest and coarsest; the extremity of the wings of Lepidopterous insects in general is fringed with longer scales than their surfaces, and even those of the last in the same wing; sometimes vary in magnitude. The little seeming tooth that projects from the middle of the posterior margin in the upper wings of Notodonta, a subgenus of Bombyx L., is merely produced by some longer diverging hairs. The shape and figure also of scales are very various--some being long and slender; others short and broad; some nearly round; others oval, ovate, or oblong; others spathulate; others panduriform or parabolical; some again almost square or rhomboidal; many triangular; some representing an isosceles triangle, and others an equilateral one; lastly, some are lanceolate and others linear; again, some have a very short pedicle and others a very long one: with regard to their extremity; some are intire, without projecting points or incisions, while others are furnished with them: of these some terminate in a single long mucro, others have several shorter ones; some are armed with teeth, varying in number from two to thirteen in different species[1962]. Many other forms might be enumerated, but these are sufficient to give you a general notion of the infinite variety of this part of the works of the CREATOR. I must next say a word or two upon their arrangement on the wing. In most instances this is in transverse lines, which sometimes vary a little from a rectilinear course, and the extremity of the scales of one row reposes on the base of those of the succeeding one, so that in this respect their arrangement is like that of tiles in a roof: in some cases it is not so regular: thus the minute scales on the wings of Parnassius Apollo, and others with subdiaphanous wings, are arranged without order; in Pieris and other Diurnal Lepidoptera, and many of the Crepuscular and Nocturnal, there appears to be a double layer of scales on both sides of the wing; the under layer usually consisting of white ones. If you denude the wings of any butterfly, which you may easily do by scraping it lightly on both sides with a penknife, you will be amused to trace the lines in which the scales were planted, consisting of innumerable minute dots: the lines of the under side, in some cases, so cut those of the upper side, as by their intersection to form lozenges. With regard to the position of the scales on the wing, they usually lie flat, but sometimes their extremity is incurved: in the beautiful Argynnis Vanillæ a very singular appearance of numerous transverse ridges is produced by the extremity of those scales that cover the longitudinal nervures of the primary wings, except at the base, being recurved.

But though the general clothing of the wings of Lepidoptera consists of these little scales, yet in some cases they are either replaced by hairs or mixed with them. Thus, in the clear parts of the wings of Heliconians, Attaci, &c., short inconspicuous hairs are planted; in a large number of the Orders the upper side of the Anal Area of the secondary wings is hairy; in several Crepusculars (Sphinx Phœnix, &c.), where there is a double layer as before mentioned, the upper one consists of dense hairs, except at the apex, and the lower one of scales; and in most of them the scales of the primary wings are piliform, and the secondary are covered by what approach very near to real hairs; many of the Attaci are similarly circumstanced: the four wings of A. Cytherea are also covered externally with hair.

7. Before I conclude this long diatribe on the organs of flight of insects, I must not omit some notice of the infinite diversity of colours with which their wings are often variegated and adorned by the CREATOR, who loves to delight us by the beauty, as well as to astonish and awe us by the immensity and grandeur of his works. Though the wings in every Order exhibit instances of brilliant and beautiful colouring, yet those of the Lepidoptera in this respect infinitely excel them all, and to these, under this head, after noticing a few in the less privileged Orders, my observations will be confined. Although in the Coleoptera the wings are seldom distinguished by their splendour; yet those of some Cetoniadæ, as Cetonia africana, are extremely brilliant, and resemble those of many Xylocopæ in the lovely violet hue that adorns them: amongst the Orthoptera some Pterophyllæ, and in the Homopterous Hemiptera some Fulgoræ, emulate the Lepidoptera in the ocelli that give a kind of life to these organs[1963]; and a vast number of the destructive tribe of locusts (Locusta Leach) are remarkable for the fine colours and gaiety of their wings[1964]; in the Neuroptera numerous Libellulinæ emulate the Heliconian butterflies by their maculation; and in the genus Ascalaphus, which represents the Lepidoptera by its clubbed antennæ[1965], many also have the resemblance increased by the painting of their wings, so that some Entomologists have actually considered some of them as belonging to that Order[1966]; the wings of the Xylocopæ, before alluded to, sometimes add to the deep tints of the violet--which also prevail in the wings of several Diptera--towards their extremity the most brilliant metallic green or copper varying,

"As the site varies in the gazer's hand,"

and even those wings that consist of clear colourless membrane are often rendered extremely beautiful from the reflection of the prismatic colours. I should undertake an endless task did I attempt to specify all the modes of marking, clouding, and spotting, that variegate a wing, and all the shades of colour that paint it, amongst the Lepidopterous tribes; I shall therefore confine myself to a few of the principal, especially those that distinguish particular tribes and families. Of whole coloured wings--I know none that dazzle the eye of the beholder so much as the upper surface of those of Morpho Menelaus and Telemachus: Linné justly observes that there is scarcely any thing in nature that for brightness and splendour can be paralleled with this colour; it is a kind of rich ultramarine that vies with the deepest and purest azure of the sky; and what must cause a striking contrast in flight, the prone surface of the wings is as dull and dark as the supine is brilliant, so that one can conceive this animal to appear like a planet in full radiance, and under eclipse, as its wings open and shut in the blaze of a tropical sun: another butterfly, Papilio Ulysses, by its radiating cerulean disk, surrounded on every side by a margin intensely black, gives the idea of light first emerging from primeval obscurity; it was probably this idea of light shining in darkness that induced Linné to give it the name of the wisest of the Greeks in a dark and barbarous age. I know no insect upon which the sight rests with such untired pleasure, as upon the lovely butterfly that bears the name of the unhappy Trojan king (P. Priamus); the contrast of the rich green and black of the velvet of its wings with each other, and with the orange of its abdomen, is beyond expression regal and magnificent. But peculiar beauties of colour sometimes distinguish whole tribes as well as individuals. What can be more lovely than that tribe of little butterflies that flit around us every where in our summer rambles, which are called blues, and which exhibit the various tints of the sky? Lycæna Adonis of this tribe scarcely yields to any exotic butterfly in the celestial purity of its azure wings: our native coppers also, Lycæna dispar[1967], Virgaureæ, &c., are remarkable for the fulgid colour of these organs; in Argynnis the upper side of their wings is tawny, spotted with black, while the under side of the secondary ones is very often adorned by the appearance of silver spots. How this remarkable effect of metallic lustre, so often reflected by spots in the wings of butterflies, is produced, seems not to have occupied the attention of Entomologists. M. Audebert is of opinion that the similar lustre of the plumes of the humming birds (Trochilus) is owing to their density, to the polish of their surface, and to the great number of little minute concave mirrors which are observable on their little beards[1968]. But these observations will not apply to the scales of the wings of butterflies, which are always very thin and generally very flat: in some instances, as in Morpho Menelaus, there appears more than one very slight channel upon a scale; but this takes place also in others that reflect no lustre. Their metallic hues must therefore principally be occasioned by the high polish of their surface and the richness of their tints. It is the purity of the white, in conjunction with their shining surface, contrasted with the dull opaque colour of the under side of the secondary wings, that causes the spots that decorate those of the Fritillaries (Argynnis) to emulate the lustre of silver. In Papilio the Trojans are distinguished by the black wings with sanguine spots, and the Greeks by the same with yellow spots; but these have proved in some instances only sexual distinctions[1969]. In the Danai candidi L. the colour of the tribe may be described as sacred to the day, since every shade, from white or the palest yellow to full orange, is exhibited by them. The yellows prevail also in those Noctuæ, the trivial names of which Linné made to end in ago, as N. Fulvago, Citrago, &c. I must not conclude this part of my subject without noticing one of the most striking ornaments of the wings of Lepidoptera, the many-coloured eyes which decorate so large a number of them. Some few birds, as the Peacock and Argus Pheasant, have been decked by their CREATOR very conspicuously with this almost dazzling glory; but in the insects just named it meets us every where. Some, as one of our most beautiful butterflies, Vanessa Io[1970], have them both on the primary and secondary wings; others, as Noctua Bubo[1971], only on the primary; others again, as Smerinthus ocellata[1972], only on the secondary: in some also they are on both sides of the wing, as in Hipparchia Ægeria[1973], and in others only on the upper side, as in Vanessa Io; in others again only on the under side, as in Morpho Teucer[1974]: in some likewise they are very large, as in the secondary wings of the same butterfly: and in others very small, as in those in the wings of the blues (Lycæna). Once more, in some they consist only of iris and pupil, as in Hipparchia Semele, and in others of many concentric circles besides, as in Morpho Teucer, &c.

v. Legs[1975]. We are next to consider those organs of motion affixed to the trunk, by which insects transport themselves from one place to another on the earth or in the water, and by which also they perform various operations connected with their economy[1976]. In treating of them we should consider their number; kind; substance; articulation with the trunk; position; proportions; clothing; composition; folding; and motions.

1. Number. Having before very fully explained to you the number and kind of the legs of insects in their preparatory states[1977], I shall now confine myself to the consideration of these organs in their perfect or last state; beginning with their number. Insects, properly so called, as I formerly observed[1978], in this state, including the anterior pair or arms, have only six legs, none exceeding or falling short of this number; but in several of the Diurnal Lepidoptera (Vanessa, &c.) the anterior pair are spurious, or at least not used as legs, the tarsi having neither joints nor claws[1979]; this in some cases is said to be only a sexual distinction[1980]. In Onitis, Phanæus, and some other Scarabæidæ M^cL., the arm has either none or a spurious tarsus or manus[1981]; which in the first of these genera is also a sexual character. From both these instances we see that walking is only a secondary use of forelegs in the insect tribes. Besides insects proper, a whole tribe of mites (Caris Latr., Leptus Latr., Astoma Latr., Ocypete Leach) have only six legs; the rest, and the Arachnida in general, have eight; in the Myriapods, Pollyxenus has twelve pairs; Scutigera has fifteen; the terrestrial Glomerides (G. Armadillo, &c.) sixteen; and the oceanic (G. ovalis) twenty; the oriental Scolopendræ Leach, twenty-one; Polydesmus has usually about thirty pairs; Craspedosoma, fifty; Geophilus electricus at least sixty; in Iulus terrestris there are more than seventy; in I. sabulosus nearly one hundred; in I. fuscus, 124; and in I. maximus 134 pairs or 268 single legs. But with respect to the Geophili, Iuli, &c., it is to be observed, that the number of pairs varies in different individuals; and the circumstance that has been before mentioned[1982], that these animals keep acquiring legs in their progress to the perfect state, instead of losing them, renders it difficult to ascertain what is the natural number of pairs in any species.

2. Kinds. Upon a former occasion I gave you a sufficiently full account of the kinds of legs[1982], and I have also assigned my reasons for giving a different denomination to the anterior legs under certain circumstances[1983]; I shall not therefore enlarge further upon this head.

3. Substance. The substance of the legs is generally regulated more or less by that of the rest of the body, only in soft-bodied insects they seem usually more firm and unbending. Each joint is a tube, including the moving muscles, nerves, and air vessels.

4. Articulation with the Trunk. M. Cuvier has observed that the hip (coxa), which is the joint that unites the leg with the body, rather inosculates, in its acetabulum, than articulates in any precise manner[1984]; but this observation, though true of a great many, will not apply universally, for the legs of Orthopterous insects, and of most of the subsequent Orders, are suspended rather than inosculating. Even in many Coleoptera a difference is observable in this respect. I have before mentioned that what are called the puncta ordinaria, which distinguish the sides of the prothorax of many Scarabæidæ and Geotrupidæ, form a base for an elevation of the interior surface with which the extremity of the base of the clavicle, which plunges deep into the breast, ginglymates[1985]; this structure may also be found in other Lamellicorns, as the stag-beetle (Lucanus) and Dynastes, that have not those excavations; in these last it is an elevated ridge forming a segment of a circle with, it should seem, a posterior channel, receiving a corresponding cavity and protuberance of the clavicle. With regard to the mid-leg, in Copris, the coxa is emboxed in a nearly longitudinal cavity of the medipectus, and the coxa of the hind-leg anteriorly is suspended to a transverse cavity of the postpectus, but posteriorly it is received by a cavity of the first segment of the abdomen; so that it may be regarded as suspended anteriorly, and inosculating posteriorly.

In some tribes of this Order, as the Weevils (Curculio L.) and Capricorns (Cerambyx), the coxæ of the four anterior legs are subglobose[1986] and extremely lubricous, and are received each by a socket that fits it, and is equally lubricous. In the bottom of this externally, and in the head of the coxa, is an orifice for the transmission of muscles, nerves, and bronchiæ; but the coxa is suspended by ligament in the socket. This structure approaches as near the ball and socket as the nature of the insect skeleton will permit; the high polish of the articulations acts the part of synovia, and the motion is in some degree rotatory or versatile, whereas in Copris, &c., lately mentioned, it seems to be more limited, and is probably, at least in the mid- and hind-legs, only in two directions; in the middle pair, probably, from the coxæ being in a position parallel with the breast, opposite to that of the hind pair. In Dytiscus L., Carabus L., and some other beetles, the coxæ, especially the posterior pair, appear to be fixed and incapable of motion. In many insects these coxæ seem to belong as much to the abdomen as to the trunk. We have just seen this to be the case in Copris, &c.; and in the Lepidoptera, if the former be separated from the latter, the legs will be detached with it.

4. Location. We are now to consider the location and position of the legs, both in general and with respect to each other. And first, as has been before stated, we may observe that, in the hexapods with wings, the arms belong to the manitrunk, and are attached to the antepectus on each side the prosternum; and the two pair of legs to the alitrunk, the mid-legs being attached to the medipectus, between the scapularia and mesosternum; and the hind-legs to the postpectus, between the parapleura and the posternum; and further, that the arms are opposed to the prothorax: the mid-legs to the mesothorax and the primary organs of flight; and the hind-legs to the metathorax and the secondary organs of flight; though in some cases the wings appear to be behind the legs and in others before them: thus, in Panorpa, the former are nearer the head than the latter; but in the Libellulina the reverse of this takes place, the legs being much nearer the head than the wings: in both cases, however, the scapularia and parapleuræ run from the legs to the wings, but in an oblique direction; and in Panorpa these pieces assume the appearance of articulations of the legs. In most of the apterous hexapods they appear to be attached laterally between the thorax and the pectus[1987]; but in the flea (Pulex) they are ventral. In this tribe the arms are usually stated to be inserted in the head[1988]: but I once succeeded in separating the head of a flea from the trunk, and these organs remained attached to the latter[1989]. As to the Octopods and Arachnidæ, in the mites (Acarus L.) they are lateral, and in their analogues, the spiders (Aranea L.), they emerge between the thorax and the breast, which last they nearly surround; in the Phalangidæ the bases of the coxæ approach near to each other, being separated only by a narrow sternum; in their antagonists, Chelifer and Scorpio, they apply to each other, the anterior ones acting as maxillæ. In the myriapods the legs of the Chilopoda Latr., and some Chilognatha, as Glomeris, are inserted laterally, a single pair in a segment; but in Iulus L. their attachment is ventral, the coxæ seem to spring from a common base, and there are two pair to each segment[1990], except the three first, which bear each a single pair.

I shall next consider how the legs are located with respect to each other. To render this clear to you I shall represent each of the variations, which amount in all to twelve in the hexapods that have fallen under my notice, by six dots.

1. [Illustration: dots] In this arrangement the legs are all planted near to each other, there being little or no interval between the pairs, and between the legs of each pair. It is exemplified in the Lepidoptera, Blatta, and many Diptera.

2. [Illustration: dots] Similar to the preceding, but the anterior pair are distant from the two posterior; exemplified in the bees (Apis) and most Hymenoptera; Chironomus; Scutellera; Pachysoma K.[1991]

3. [Illustration: dots] Like the last, but the posterior pair is distant from the two anterior. Examples: Silpha, Necrophorus, Telephorus, &c.

4. [Illustration: dots] Similar to the last, but the legs of the posterior pair are more distant from each other than the four anterior. Ex. Curculio L.

5. [Illustration: dots] The legs of each pair near each other, but the pairs distant. Ex. Gibbium.

6. [Illustration: dots] Both the legs of each pair and the pairs distant. Ex. Blaps, &c.

7. [Illustration: dots] Anterior pair distant from the two posterior, and the legs of the middle pair rather more distant from each other than those of the other pairs. Ex. Scarabæus M^cL.

8. [Illustration: dots] Like the preceding, only the legs of the middle pair are at a much greater distance from each other. Ex. Copris M^cL.

9. [Illustration: dots] Legs of the two posterior pairs distant. Ex. Hister, Scaphidium.

10. [Illustration: dots] Like the preceding, but the posterior legs more distant than those of the middle pair. Ex. Lygæus.

11. [Illustration: see previous] Like the last, but the legs of the anterior pair also distant. Ex. Velia.

12. [Illustration: see previous] The arms distant, intermediate legs more distant, posterior legs close together. Ex. Byrrhus L.

5. Proportions. In general the legs of some insects are disproportionally long and slender, as in Phalangium Opilio and some species of Gonyleptes[1992]: those of others are disproportionally short, as in Elater, &c. With regard to their relative proportions, the most general rule is, in Hexapods, that the anterior pair shall be the shortest and most slender, and the posterior the longest and thickest; but there are many exceptions: thus, in Macropus longimanus, Clytra longimana, &c., in the male the arms are the longest; again, a thing that very rarely occurs, in the same sex of Podalirius retusa the intermediate legs are the longest[1993]; but in Rhina barbirostris and many weevils they are the shortest: in Saperda hirtipes Oliv.[1994] the hind-legs are disproportionally long: with regard to thickness, they are in general extremely slender in Cicindela, and in the Scarabæidæ very thick. In Goliathus Cacicus the arms are more robust than the four legs[1995]; in Gyrinus the latter are more dilated than the former; in many Rutelidæ, and particularly in the celebrated Kanguroo beetle (Scarabæus Macropus Franc.) the hind-legs are much the thickest; in a new genus of weevils from Brazil (Plectropus K.), the intermediate pair are more slender than either the arms or the posterior pair.

6. Clothing. The hairs on the legs of insects, though at first sight they may seem unimportant, in many cases are of great use to them, both in their ordinary avocations and motions: but as most of these were sufficiently noticed when I treated of the sexes of insects[1996], I shall not here repeat my observations, but confine myself to cases not then adverted to. Some insects have all their legs very hairy, as many spiders, the diamond beetle (Entimus imperialis), or at least a species very near it and common in Brazil[1997], &c.: in others they are nearly naked, as in the stag-beetle. In the Crepuscular Lepidoptera (Sphinx L.) and some of the Nocturnal ones (Bombyx L.) the thighs are much more hairy than the rest of the legs: and in Lucanus, Geotrupes, and many other Lamellicorns, &c., the anterior ones have a yellow or golden spot at their base, composed of decumbent hairs, which prevent them from suffering by the violent friction to which they are exposed in burrowing. In most Petalocerous beetles the tibiæ are set with scattered bristles, and sometimes the thighs. The Tiger beetles (Cicindela) are similarly circumstanced: but the bristles, which are white, are generally arranged in rows. In Dytiscus, Hydrophilus, &c., the four posterior tarsi; and in Notonecta the posterior pair, and also the tibiæ--are fringed on each side with a dense series of hairs, which structure assists them in swimming[1998]. The tarsi, especially the anterior pair, in a certain family of Lamia F. (L. papulosa, &c.[1999]), are similarly fringed, only the hairs curl inwards; and the hand in Sphex and Ammophila, but not in Pelopæus and Chlorion, is fringed externally with long bristles.

7. Composition. With regard to their composition, both arms and legs generally consist of five pieces, which Entomologists have denominated--the coxa or hip--the trochanter--the femur or thigh--the tibia or shank--and the tarsus or foot. Where the structure and use of the fore-leg is different from that of the four hind-legs, I propose calling these pieces by names corresponding with those which anatomists have appropriated to the arm in the higher vertebrate animals: thus, as you will see in the table, I call the whole fore-leg the brachium or arm; and the coxa becomes the clavicula or collar-bone; the trochanter, the scapula or shoulder-blade; the femur, the humerus or shoulder; the tibia, the cubitus or arm; the tarsus, the manus or hand. But let me not lead you to suppose that the pieces, either in the arms or legs of insects, which are there named after certain others in vertebrate animals, precisely correspond with them--by no means--since that is a very doubtful point; and some of them, as the trochanter, clearly do not. Many gentlemen skilled in anatomy, as I have before observed[2000], have thought that what is regarded as the coxa in insects really represents the femur: but there are considerable difficulties in the way of this supposition, several of which I then stated. I shall not however enter further into the subject, and take the above names; since this application of them is so general and so well understood, except with regard to the fore-leg, under certain circumstances, as I find them. I shall now consider them in the order in which I have named them.

a. Coxa or Clavicula[2001]. The coxa is the joint that connects the leg with the trunk of the insect. With regard to their shape, the most general form of the four anterior is more or less that of a truncated cone: in the Staphylinidæ, however, they tend to a pyramidal or four-sided figure; as do the whole six in the Trichoptera: in numbers of the weevils and capricorns they are subglobose; in the Lamellicorns they are mostly oblong, and not prominent: the posterior pair in the Coleoptera are generally flat and placed in a transverse position, and more or less oblong and quadrangular: in Elater, &c., they are cuneiform: in Haliplus Latr. they are dilated, and cover the thigh[2002]: in Buprestis, Copris, &c., they have a cavity that partly receives it: the corresponding part, the clavicle, in the arm of Gryllotalpa, is very large and remarkable; viewed underneath it is triangular, and trifid where the trochanter articulates with it: in that of Megachile Willughbiella the clavicle is armed with a spine[2003]. As to their proportions, the most general law seems to be, that the anterior pair shall be the shortest and smallest, and the posterior the longest and largest. In some instances, as in Buprestis, the two anterior pair are nearly equal; in others (Mantis, Eurhinus K.), the anterior are the longest, in the former as long as the thigh, and the four posterior the shortest: in the Trichoptera, Lepidoptera, &c., all are nearly equal; in Mantis the two posterior, and in Phengodes the intermediate pair are the largest; but in Necrophorus they are the smallest:--though almost universally without articulations, in Galeodes the clavicle consists of two and the coxa of three[2004].

b. Trochanter or Scapula[2005]. This is the second joint of the leg: and if the coxa is regarded as the analogue of the thigh in vertebrate animals, this should seem to represent the patella or rotula, vulgarly called the knee-pan. Latreille and Dr. Virey consider this articulation as merely a joint of the coxa[2006]; but if closely examined, especially in Coleopterous insects, you will find it so fixed to the thigh as scarcely to have separate motion from it, and in many cases it seems to be merely its fulcrum; but I am not aware that any instance occurs in which it has not motion separate from that of the former joint.

As to its articulation with the coxa,--in the Coleoptera it appears to be of a mixed kind; for it inosculates in that joint, is suspended by ligament to its orifice, and its protuberances are received by corresponding cavities in it; and its cavities receive protuberances, which belongs to a ginglymous articulation. I have observed two variations in this Order, in one of which the motion of the thigh and trochanter is only in two directions, and in the other it is nearly versatile or rotatory. The Lamellicorns afford an example of the first, and the Rhyncophorous beetles or weevils of the second. If you extract from the coxa the thigh with the trochanter of the larger species of Dynastes M^cL., you will find that the head of the latter is divided into two obtuse incurving lobes or condyles: that on the inner side being the smallest and shortest, and constricted just below its apex: and that under this is a shallow or glenoid cavity, terminating posteriorly in a lubricous flat curvilinear ridge. If you next examine the trochanter in articulation with the coxa, you will perceive that the head of the former inosculates in it, that the lower condyle is received by a sinus of the coxa, which also has a lubricous very shallow cavity corresponding with the ridge, in which it turns; and in the head of the coxa, on the lower side, is an external condyle, which is received by a sinus common to both, of the head of the thigh and of the exterior side of the trochanter[2007], in which it likewise turns: this last condyle has also an internal protuberance, which appears to ginglymate with a cavity of the trochanter: from this structure the leg is limited chiefly to a motion up and down upon two pivots, or to fold and extend itself. You will find an articulation very near this, but on a smaller scale, in the stag-beetle. In the other kind of articulation, which admits of freer motion, the head of the trochanter is prolonged, and the process terminates in a short interior condyle, which appears to work in a corresponding cavity of the interior of the coxa; and the base of the process is encompassed by a ridge with a cavity behind it, which is received by another of the lower part of that piece, and admits a corresponding ridge--a structure that allows a rotatory motion. In the hind-legs of this tribe the motion is chiefly limited to folding and extending; in Carabus, &c., also the head of the trochanter is nearly hemispherical, and the articulation approaches ball and socket. In most of the other Orders, the Hymenoptera excepted, there is little or no inosculation, the trochanter being simply suspended by ligament to the coxa as well as to the thigh; its connection with the latter is similar in Coleoptera; but in Cicindela, &c., it inosculates in it. The part we are considering varies in its position with respect to the thigh: in the hind-legs of Carabus, &c., it forms a lateral fulcrum on the inner side of that part, and does not intervene between its base and the coxa; the muscles from the latter entering the former, not at the bottom of the base, but at its side: but in the four anterior legs it forms their base, as it does in all the legs in Apion, and in all the Orders except the Coleoptera, cutting them entirely off from contact with the coxa: in the Lamellicorns they cut off part of the base obliquely, but so as to permit their coming in contact with the condyle of the coxa, as before mentioned. In the Ichneumonidæ and some other Hymenoptera the trochanter appears to consist of two joints particularly visible in the posterior legs[2008].

As to size in general,--the part in question is smaller than the coxa; but in Notonecta it is larger, and in the dog-tick (Ixodes Ricinus) longer than that joint. It exhibits few variations in its shape or appendages worthy of particular notice. In general, in the Coleoptera it is triangular or trigonal; but in Carabus L., in the hind-leg it is oblong or rather kidney-shaped; in that of Necrophorus[2009] it terminates in one or two teeth or spines, varying in length in the different species: in the other Orders it is not remarkable in this respect.

c. Femur or Humerus[2010]. The femur or thigh is the third, and usually the largest and most conspicuous joint of the leg. In the hypothesis before alluded to[2011] it is considered as the analogue of the tibia of vertebrate animals. With regard to the articulation of this part with the trochanter, it has been sufficiently explained under that head, and that with the tibia I shall treat of when I come to that joint. As to the size of the thighs, and their relative proportions to each other and to the remaining joints of the leg, the most general law is, that the anterior pair shall be the shortest and smallest, and the posterior the longest and largest. With respect to the remaining articulations, most commonly the thigh is longer and larger than the tibia, and the tibia than the tarsus. But there are numerous exceptions to both these rules. With respect to the first, we may begin by observing that the increase of the magnitude of the thigh, from the anterior to the posterior pair, is usually gradual: but in many jumping insects, and likewise many that do not jump, the posterior pair are suddenly and disproportionally thicker than the rest[2012]. Again, in many insects the anterior pair are the longest and thickest, as in Macropus longimanus, Bibio, Nabis, &c.: in others, the intermediate exceed the rest in magnitude, as in Onitis Aygulus, cupreus; Sicus flavipes, &c.; in many Lamellicorns all the thighs are incrassated and nearly equal in size: but in some, as Ryssonotus nebulosus M^cL.[2013], the intermediate pair are rather smaller than the rest. With respect to the second rule--in some, as in the male of Macropus longimanus, the anterior tibia, though more slender, is longer than the thigh; in Hololepta maxillosa it is longer and more dilated; in Lamia marmorata, or one related to it from Brazil, the intermediate pair are longer; in Ateuchus gibbus and others of that tribe the posterior thighs are smaller than the tibiæ: and, to mention no more; in Callichroma latipes the posterior tibia is wider than the part last named. Again, the tarsi are as long as either tibia or thigh in many of the larger Dynastidæ, as Megasoma Actæon, &c.; longer than either in Melolontha subspinosa F.; and in Tiphia, Scolia and affinities, often as long, or longer than both together.

As to shape,--the thigh, especially in the fore-leg, varies considerably: most generally it is flat, linear, and a little thicker where it is united to the tibia, on the outer side convex, and concave next the body; but in many it is gradually thicker from the base to the apex: in some Cerambyces (C. thoracicus) it is clavate; in others of this genus and Molorchus they may be called capitate; in Pterostichus they are rather lanceolate; in Onitis Sphinx the humerus is triangular, and the intermediate thigh rhomboidal; in Bruchus Bactris it is bent like a bow; and in some Brazilian Halticæ it is nearly semicircular. The humerus in Phasma is attenuated at the base; in Empusa gongyloides it is at first ovato-lanceolate, and terminates below in a kind of footstalk[2014]; in Phasma flabelliforme it is dolabriform[2015]; in Mantis often semioval or semielliptical, and thickest at the inner edge, which affords space for two rows of spines with which it is planted. In Phyllium siccifolium all the thighs are furnished on both sides with a foliaceous appendage nearly from base to apex[2016]: in a species of Empusa (E. macroptera), the four posterior ones are so distinguished only on their posterior side[2017]: others of this last genus, as E. gongyloides, have an alary appendage on both sides at the apex of these thighs[2018]; and another family, as E. pauperata, have only one on the posterior side[2019]. The thighs of no insect are more remarkable for their elegant shape,--tapering gradually from the base to the apex, where they swell again into a kind of knee,--than the posterior ones of the locusts (Locusta Leach); each side of these thighs is strengthened with three longitudinal nearly parallel ridges, and the upper and under sides are adorned by a double series, in some coalescing as they approach the tibia, of oblique quadrangular elevations resembling scales[2020].

I shall next say a few words upon the spines and other processes which arm the thigh. Those moveable ones of Mantis which help to form a fearful instrument of destruction, have just been mentioned, and similar ones, but less conspicuous, arm the intermediate thighs of Sicus flavipes: other appendages of this kind are for a less destructive purpose--to keep the tibia when folded in its place. This seems to be the use of the serratures and spine that arm the thigh of Bruchus Bactris, or the Hymenopterous genera Leucospis, Chalcis, &c.; in Onitis Aygulus a short filiform horn arms the humerus, and a longer crooked one that of many species of Scaurus[2021]. In many Stenocori the thighs terminate in two spines, and in Gonyleptes K. the posterior ones are armed internally with very strong ones; with which, as the legs converge at their knee[2022], they may probably detain their prey. The knee-pan (Gonytheca) of the thigh, or the cavity at its end, which receives the head of the tibia, is very conspicuous in the weevils; but in no insects more than in Locusta[2023], in which tribe it deserves your particular attention.

d. Tibia or Cubitus[2024]. The tibia or shank is the fourth joint of the leg, which according to the hypothesis lately alluded to is the analogue, in the anterior leg of the carpus or carpal bones, and in the four posterior ones of the tarsus or tarsal bones of vertebrate animals. This may be called the most conspicuous of the articulations of the leg; for though it is generally more slender and often shorter than the thigh, it falls more under the eye of the observer, that joint being more or less concealed by the body: it consists in general of a single joint; but in the Araneidæ and Phalangidæ it has an accessory one, often incrassated at its base, which I have named the Epicnemis[2025].

With respect to the articulation of the tibia with the thigh--we may observe that in general it is by means of three processes or condyles, two lateral and one intermediate, of the head of the former joint[2026]: the lateral ones are usually received by a cavity or sinus of the gonytheca of the thigh[2027]; and upon these the tibia turns, with a semirotatory motion up and down as upon a pair of pivots: at the same time the mola or head of the latter joint, which has often a flexure so as to form an elbow with the rest of it, inosculates in the gonytheca, and is also suspended by ligament to the orifice through which the muscles, nerves, and bronchiæ are transmitted: so that in fact the articulation, strictly speaking, belongs exclusively to none of the kinds observable in vertebrate animals, but partakes of several, and may properly be denominated a mixed articulation,--a term applicable in numerous instances also to the other articulations of the legs of insects. In the different Orders some variations in this respect take place,--I will notice some of the most remarkable. In no Coleopterous insects is the structure more distinctly visible than in the larger Lamellicorns. In Copris bucephalus, for instance, if you divide the thigh longitudinally, you will find on each side, at the head, that it is furnished with a nearly hemispherical protuberance, perforated in the centre for the transmission of muscles, and surrounded externally by a ridge, leaving a semicircular cavity between them[2028]: if you next examine the tibia, after having extracted it, you will find on each side, at the base, a cavity corresponding with the protuberance of the thigh which it receives, having likewise a central orifice, and surrounded by a semicircular ridge corresponding with the cavity in the thigh in which it acts: below this ridge another cavity, forming a small segment of a circle, receives the ridge of the thigh[2029]. You will observe that the ridge of the tibia represents the lateral condyle lately noticed: in the Dynastidæ this is more prominent, and often forms a smaller segment of a circle. In these also the protuberance of the thigh is more minute, and its ridge is received by a cavity of the tibia nearly semicircular[2030]; in Geotrupes Latr. the articulation is not very different, though on a reduced scale; in Calandra Palmarum the lateral condyles of the tibiæ are flatter and broader[2031]; and the articulation not being quite so complex, this joint is kept steady by an intermediate process observable in the gonytheca[2032]. From the above description it appears that the dislocation of the tibia is effectually prevented in the Lamellicorns by the protuberance and ridge of the thigh working in their corresponding cavities, while the condyle of that part turns with a rotatory motion in the cavity of the thigh. In the Orthoptera Order the tibia is suspended by a ligament, in the gonytheca the lateral condyles, which are very prominent, working in a sinus of that part[2033]. The subsequent Orders exhibit no very striking variations from these types of articulation, I shall therefore not detain you longer upon this head.

With regard to the proportions and magnitude of the joint we are considering,--the most general law is, that the anterior pair should be shorter and more slender than the intermediate; and the intermediate than the posterior; and that all the tibiæ should be shorter and more slender than the thighs, and longer and thicker than the tarsi. Various exceptions, however, to this rule in all these cases might be produced; but I shall only observe that in all those insects in which the fore-legs are calculated for digging or seizing their prey, as in the Petalocerous beetles, the Gryllotalpa, Mantis, &c., this joint of the leg is usually much enlarged and more conspicuous than the others.

As to its figure and shape--most commonly the tibia grows thicker from the base to the apex, as in the majority of Coleoptera, Hymenoptera, &c.; in the Orthoptera, Neuroptera, &c., it is generally equally thick every where. Another peculiarity relating to this head observable in it, is its tendency to a trigonal figure: this, however, though very general, is not universal;--thus, in some Orthoptera, as Pterophylla K., its horizontal section is quadrangular; in others, as Locusta Leach and many other insects, it is nearly a circle; in some scorpions it is almost a hexagon. The superficial shape also of this joint in numerous instances is more or less triangular, but it sometimes recedes from this form:--thus, in Callichroma latipes it is a segment of a circle; in some Empides it is clavate; in Onitis Sphinx, dolabriform; in the Orthoptera, Neuroptera, &c., it is usually linear; in some Lygæi it is angular[2034]: but the most remarkable tibiæ in this respect are those of such species of this last genus as have the posterior ones winged or foliaceous, so that they resemble the leaf of some plant--the tibia being the rachis, and the wing (which in some species is veined) representing the leaf itself. This structure is exemplified in Lygæus compressipes, phyllopus, foliaceus, &c.[2035] Under this head I must say a few words upon the flexure of this joint, which in some cases merits notice. I have before mentioned its bend at the knee[2036] or base: the apex also is sometimes incurved--in the anterior one of the male of Macropus longimanus so as almost to form a hook[2037]: in Lygæus Pharaonis the posterior pair are flexuose[2038]; in Bruchus Bactris, Leucospis, and several species of Chalcis, these tibiæ curve so as to adapt themselves to the bend of the thigh when folded. The notch on the inside of the anterior pair, in a large majority of Carabus L., armed above by a spur[2039], a structure which probably assists them in seizing and detaining their prey, may also here be introduced: in the generality it is a little removed from the apex of the joint in question; but in Pamborus it is very near to it, and in Cychrus, Carabus, &c., it becomes obsolete. I may mention here also a singular character which distinguishes the cubit of both sexes of Gryllus campestris, domesticus, &c. At the base there is an aperture which passes through the joint--anteriorly it is oval, and posteriorly elliptical and much larger, and on both sides is closed by a tense membrane.

The most striking peculiarities as to the clothing of his joint have been chiefly noticed under the sexual characters of insects[2040], but some appear not to be of that description. In Sphæridium Leach, while the thighs and tarsi are naked, the posterior tibiæ are remarkably beset with stiff bristles; in Empis pennipes they are thickly fringed on both sides; in Scarabæus M^cL. only externally, and in Dytiscus serricornis internally; in Necydalis barpipes K. this fringe is longer at the apex; and in Saperda hirtipes Ol. the same tibiæ at that part are adorned with a large brush, like that observable in the antennæ of some Lamiæ[2041].

I must next call your attention to the teeth, spines, and spurs with which the tibiæ of insects are sometimes armed. With regard to teeth, you have doubtless often observed those that distinguish the cubitus of the arm of most Lamellicorn beetles: these vary in number from one, as in Trox suberosus, to seven, as in Geotrupes autumnalis; but the most universal number is three: in some species of Geotrupes, as G. stercorarius, &c., the third tooth from the apex, and those that follow it, may be called double. These teeth, in their cubit or anterior shank, doubtless assist these insects in burrowing. The four posterior tibiæ in this tribe are also distinguished by a kind of teeth which occupy their whole diameter, and resemble so many steps. I have before noticed the remarkable cubit of the Gryllotalpa, and likewise that of Scarites, Pasimachus, &c., in which some of the teeth are prolonged into spines[2042], which are the next description of tibial arms that I mentioned. Spines are of two kinds--those which are merely processes of the crust of the tibia, and those that are implanted in it, and seem to have a gomphosis or perhaps an amphiarthrosis articulation[2043]. An instance of the first kind may be seen in the hind-legs of some grasshoppers[2044] (Locusta Leach), the Rutelidæ, &c. though in others they are implanted:--of the second, in the cubitus of the Mantidæ, and of all the tibiæ of the dragon-flies (Libellulina M^cL.)[2045];--and of both kinds in the hind-legs of Acrida K., those which arm the upper angles of the tibiæ being processes, and those of the lower being implanted. The term spine I think ought to be restricted to the first kind; the second ought rather to be denominated spurs (calcaria), and may perhaps be regarded as in some degree synonymous with those most important appendages of the joint in question, that are implanted in or near their apex, which have been hitherto distinguished by this last denomination, and which I am next to consider. But though I have not altered a term generally adopted, I must here express my opinion that they ought rather to be considered as minute toes or fingers, and that the denomination best agreeing with their functions, as accessories to the main toe, would be digituli: this is proved particularly by a character peculiar to those of many species of the genus Cimbex amongst the saw-flies, in which these organs are furnished with a sucker or pulvillus (as they are also in Œnas a kind of blister beetle), as well as the joints of the tarsi[2046]; which makes it evident that they are applied by the animal to surfaces, and assist it in walking or climbing; and in general it may be observed that in most insects their principal use is connected with these motions, and with burrowing. This circumstance tends to prove that the generality of insects (for all have not these organs) have really a didactyle or tridactyle hand or foot; and the hypothesis so often alluded to--that the cubitus or tibia, &c., is really analogous to the carpus or tarsus in vertebrate animals[2047]--seems to receive no small confirmation from it; since, if the spurs be really analogous to fingers or toes, the part they articulate with cannot be the tibia, &c. Though the parts in question did not escape the notice of Reaumur, Linné, De Geer, Latreille, &c., yet they have not been employed in the determination of tribes, genera, &c., except by the author last named, but perhaps adopted from Bonelli[2048], in the subgenera Zabrus and Pelorus: in many instances, however, they afford excellent subsidiary characters, sometimes common to a whole Order, and at others distinguishing its various subdivisions. With regard to their number--I have noticed many variations which I will now state to you, first observing that I shall express them by three figures, the first representing the number of spurs on the anterior leg, the second that of those on the intermediate, and the third on the posterior; and where there are spurs, as in the Trichoptera and Lepidoptera, on the middle as well as at the end of the tibia, I shall express it by one figure over another, the upper one representing the number of the middle spurs. If you make an examination yourself, it will be proper to remind you that these little organs are extremely liable to be broken off, but the socket in which they were planted is usually very visible. The most natural number is represented by 2:2:2; this you will find very prevalent in the Coleoptera Order, as in the Predaceous and numerous other beetles: in the Orthoptera and Hemiptera Orders, however, I have not discovered an instance of it; but in all the rest it more or less occurs: next to this number--tibiæ with obsolete or no spurs seem most prevalent, particularly in the Hemiptera; not a single instance of an insect furnished with them occurring to me in the Heteropterous section; and it is doubtful whether there are any in the Homopterous.--Having stated the most universal structure in this respect, I will next consider the Orders seriatim. Amongst the Coleoptera though the numbers 2:2:2 are most frequent in occurrence, yet there are numerous exceptions. Thus, in the Lamellicorns, 1:1:1 represents the calcaria of one tribe of the Scarabæidæ M^cL. formed of the genus Scarabæus M^cL.; 1:2:1 represents those of another tribe of that family, including the subgenera Ateuchus, Copris, Phanæus, &c.; 1:2:2 again forms the character in this respect of Aphodius and the great majority of the Lamellicorns; while 2:2:2 is confined in this section to Æsalus F. and Melolontha chrysomeloides Schranck (Psephus M^cL. MS.). In the other tribes of Coleoptera other numbers occur. Thus, 0:1:1 characterizes Hylœcetus; 0:1:2 Mordella; 0:2:2 Macropus; 1/1:2:2 Harpalus, and all those Carabi L., except Zabrus, that have a notch in their anterior tibiæ; 1/2:2:2 Zabrus. In the Orthoptera Order it is not easy to distinguish the real spurs from the implanted spines that frequently arm the legs: these in Blatta are extremely numerous, even at the apex of the tibiæ; but I cannot distinguish any that can be regarded as true analogues of the former: the most natural number of spurs in this Order is represented by 0:0:4; this you will see in all the Locusts; in Acrida, Conocephala, Pterophylla; and in Truxalis, Pneumora, &c.; in Phasma there are none. In Mantis, if the terminal process of the cubitus is excluded, it will be 0:2:2; in Gryllotalpa, admitting the terminal teeth of that part[2049] as analogues of spurs, the number is 4:4:4; in Tridactylus Latr. 0:0:5[2050]; in Gryllus Latr. 3:3:5; in Gryllus monstrosus, 4:4:6. In the whole Hemiptera Order I have discovered no instance of an insect furnished with the real spurs: for though in Tettigonia F., Cercopis, &c., there are implanted spines in the posterior tibia, and several at the apex, there are none of them clearly analogous to real spurs. In the Lepidoptera the most general arrangement appears to be 1/0:2:2/2; and next to this, 1/0:2:2. In this Order most commonly there is no spur at the end of the cubit, but one resembling a thumb[2051] arms its middle; in Pieris, &c., this thumb is not present, so that the number is 0:2:2; in Agarista Leach, Erebus, &c., you will find 1/0:2:4, the posterior calcaria being all terminal; and in Attacus Atlas, all these organs are obsolete except the thumb. In the Neuroptera the most general arrangement is 2:2:2; but in the Libellulina, although the legs are very spinose, there are no spurs. In the Trichoptera K., in Phryganea rhombica and affinities, the number of them is expressed by 1/2:1/2:1/2; and in those with long antennæ, P. atra, &c., by 2/2:2/2:2/2. In the Hymenoptera the number 1:2:2 is most prevalent; and next to this, as in Apis L., 1:1:2. In the Ichneumones minuti L. the spurs are 1:1:1; in Atta Latreille, a kind of ant[2052], 1:0:0. In the Diptera it is often difficult to distinguish the spurs from the spines; but the number most universal is, I think, 2:2:2; in Tipula it is 1:2:2; in the Tabanidæ 0:2:0; and in Culex, Limonia, &c., there are none. Amongst the insects with more than six legs, most commonly the tibiæ have no spurs; but in the Araneidæ each is armed with two, a circumstance which also distinguishes the corresponding joint of the pedipalpi.

These little organs inosculate each in an appropriate socket of the end, or in many cases of the middle of the tibia; and that part of their head or base that is received by it, is often constricted for the purpose: from hence it follows that they are capable of some degree of motion, but in some insects, as those on the four posterior legs of Scarabæus sacer and its more immediate affinities, and those at the end of the cubit of Gryllotalpa, they are immoveable, and appear almost processes of the joint to which they belong. They are commonly sharp, of a subtriquetrous figure, with the lower side flat: where there are two, the outer one is usually the longest; and in general the spurs on the hind legs are longer than those on the four anterior: but there are exceptions--thus, in Acanthopus Latr. the intermediate spurs are the longest; and in Cicindela the anterior are longer than the former; in Blaps mortisaga those on all the legs are nearly equal in length. They vary sometimes in shape--those on the middle of the cubit of many Lepidoptera, which may be regarded as a kind of thumb[2053], are of a lanceolate shape; in Meloe the external posterior one is flat and obtuse; in Œnas Latr. it is obconical, concave at the extremity, and apparently furnished with a sucker; in Ateuchus smaragdulus the anterior, and in Copris Carolina the posterior is forked and emarginate; in Sirex the former is hooked and winged; in Lamprima it is triangular and dilated; in Aphodius analis it is dolabriform; in Dynastes retusus and Juvencus the spurs are bent like a bow. In many Hymenoptera, as the Sphecidæ, they are pectinated[2054], with a series of minute parallel spines--a structure which assists the animal in burrowing[2055]; in Acanthopus Latr. they are armed with little teeth or spines[2056]; in the hive bee the spur of the cubit is furnished with a membranous appendage which I have called the velum[2057]; and in a subgenus related to Saropoda Latr. (Ctenoplectra K. MS.), the interior spur of the posterior leg is crescent-shaped, fixed transversely, and fitted on the inner side with a membrane, the edge of which is finally pectinated.

e. Tarsus or Manus[2058]. This is the last portion of the leg, usually supposed to be analogous to the hand or foot of vertebrate animals; but, according to the hypothesis so often alluded to, rather the representative of their jointed finger or toe. In treating of this part I shall consider its articulation with the tibia, and of its joints inter se; the number of those joints; their proportion and shape; their parts and appendages.

I seem to have observed three kinds of tarsal articulation. The first is a species of enarthrosis or ball and socket, the joints terminating in a globular head, perforated indeed for the transmission of muscles, &c., and which is received by a corresponding cavity of the tibia or preceding joint, as may be seen in many weevils (Curculio L.[2059]). This admits of some rotatory motion.--The second is a mixed articulation between enarthrosis and ginglymus, when at the base of the ball a deep transverse channel receives a corresponding ridge of the tibiæ or preceding joint: this may be found in Rutela and probably many other Lamellicorn beetles; and something very similar in the Predaceous ones.--The third kind is where there is little or no inosculation, and the joints are scarcely more than suspended: this takes place in the Orthoptera, Neuroptera, &c.; but in Blatta and the hind legs of Mantis there is some approach to the foregoing kinds.

We are now to consider the number of joints of the tarsus, which varies considerably in the different Orders, and in one has been assumed as a clue for a subdivision of it into sections[2060], which, though not perfectly natural, is very convenient, and has been adopted by most modern Entomologists. In treating of this head, I shall use those denominations that have been employed by M. Latreille and others to express the variations of the number of the tarsal joints in the Coleoptera, but shall apply them to insects in general. Insects in this view, therefore, may be called pentamerous; heteromerous; tetramerous; trimerous; dimerous; or monomerous.

Pentamerous insects are those which have five joints in all their tarsi. This is the most universal, and may be called the natural number of these joints. More than half the Coleoptera belong to this section; in the Orthoptera--the Blattidæ, Mantidæ, and Phasmidæ; all the Lepidoptera except those butterflies called tetrapi (Vanessa, &c.); all the Trichoptera, Hymenoptera, and Diptera; in the Neuroptera--Ascalaphus, Myrmeleon, Hemerobius, Corydalis, &c.; and in the Aptera--Pulex[2061].

Heteromerous insects are those in which the number of these joints varies in the different pairs of legs[2062]. These variations, like the spurs, may be expressed by three figures, the first representing the anterior tarsus, the second the intermediate, and the third the posterior. I begin with 5:5:4. This number represents those beetles that have been exclusively regarded as heteromerous by modern Entomologists--of this description is the Linnean Tenebrio, Meloe, &c., now subdivided into numerous genera; they have five joints in the two anterior pair, and four in the posterior. The tarsal joints of the aquatic genus Hydroporus (a singular anomaly in the Order to which they belong) are expressed by 4:4:5, thus reversing the number in the preceding tribe: other Heteromerous genera are to be found amongst the Hemiptera. Thus, in Ranatra the numbers are 2:1:1; in Sigara and Nauceris 1:2:2; in a new subgenus between Belostoma and Naucoris (Xiphostoma K. MS.), brought by Dr. Bigsby from Canada, 3:2:2; in the Lepidoptera the butterflies called tetrapi (Vanessa, &c.) may be expressed by 1:5:5. Amongst the Aptera and Arachnida there are three remarkable genera, which if their pedipalps are included may be deemed Heteromerous. I mean Phrynus, Thelyphena, and Galeodes;--in the former the numbers will be *:4:4:4, the asterisk denoting more than ten; in the second, 8:4:4:4.; and in Galeodes (in which the first pair of pedipalps are not chelate, the mandibles performing their office) the numbers are 1:1:3:3:3.[2063]

Tetramerous insects are those in which all the tarsi consist of four joints; these in the Coleoptera are next in number to the pentamerous--indeed a very large proportion of them strictly speaking are really of the latter description, since in Linné's four great genera, Curculio, Cerambyx, Chrysomela, and Cassida and some others, the claw-joint (ungula) consists of two articulations, one very short, forming merely the ball at its base[2064], which inosculates in the socket of the preceding joint, and the other constituting the remainder: if you carefully separate these two pieces, you will find that the last inosculates in the summit of the ball, and is moved by appropriate muscles[2065]. This structure probably permits the readier elevation and depression of this joint. In the Orthoptera the tetramerous genera are those which Linné called Tettigonia amongst his Grylli (Locusta F.); Acheta monstrosa also, and in the Neuroptera, Raphidia belong to this section.

Trimerous insects are those whose tarsi consist of only three joints. Amongst beetles the Lady-birds (Coccinella L.) are remarkable for this structure, but in them the claw-joint is also biarticulate, so that strictly speaking they are tetramerous; in the Orthopterous Order the migratory locusts (Locusta Leach) belong to this section, as likewise Gryllus Latr. and Gryllotalpa Latr.: in the first of these genera is an appearance of there being more joints in the tarsus, because there is more than one cushion below the first[2066]. To this section also belong the great majority of the Hemiptera, excluding only those tribes that connect the two sections of the Order constituting the two Linnean genera Nepa and Notonecta; the Libellulina likewise belong here, as do also the Scorpionidæ and Scolopendridæ.

Dimerous insects are those that have two joints in all their tarsi. Such are the Pselaphidæ in the Coleoptera Order[2067]; in the Hemiptera--Belostoma and Notonecta; in the hexapod Aptera--Pediculus; in the octopod--the Acari of Linné; in the myriapod--Iulus; and in the Arachnida--the Araneidæ.

Monomerous insects are those which have only a single tarsal joint. Only one Coleopterous and also one Hemipterous genus is so distinguished: the first is Dermestes Armadillus De Geer[2068], and the second the common water-scorpion, Nepa Latr. Among the Aptera we find Nirmus, Podura, Sminthurus, &c., that belong to this section.

To the above sections another may be added for those insects whose tarsi have more than five joints, which may be denominated Polymerous. Here belong the genera Gonyleptes K., Phalangium and Scutigera Latr. In the first the number of joints varies from six to eleven, and in the two last they far exceed that number, amounting in some species of Phalangium to more than fifty, and becoming convolute like the antennæ of Ichneumons[2069].

I am next to notice the proportions and shape of the tarsus and its joints. The most general law is, that it shall be shorter and more slender than the tibia; but it admits of several exceptions--thus, in Megasoma K.[2070], in all the legs; in Agrostiphila M^cL. MS.[2071] in the intermediate, and in Amphicoma lineata in the posterior pair the tarsi are the longest; in Trichius Delta these last are longer than the thigh and tibia together. In some insects the tarsi are disproportionally short, as in Cassida, the Pselaphidæ, Locusta Leach, &c. Though generally more slender than the tibia, in several instances they are as thick or thicker, or more dilated, as in most of the tetramerous beetles, which being climbers require a dilated tarsus. Again, comparing the three pairs of this joint with each other, the most general rule is, that the anterior should be the shortest, and the posterior the longest: but in some, as the Capricorn beetles, &c., they are nearly equal in length; in others, as Lytta marginata, the anterior pair, and in Rhipiphorus the intermediate, are the longest; in Trichius Delta these last are the shortest. With respect to thickness, the anterior tarsi, except in many males[2072], are not very strikingly different from the rest.

With regard to the proportion of the joints of the tarsus to each other,--according to the most general law, the first is the longest, the last next in length, then the second and third, and the fourth is the shortest. In Gonyleptes K. and other Phalangidæ the first is almost thrice the length of all the rest taken together; but there are numerous exceptions to the rule. In the female Carabi the first joint is not longer than the last, and in the males not so long; and in Hydrophilus, &c., it is the shortest of all. Again, the second joint is longer than the three following ones in Dasytes ater[2073]; and than the last in Cicindela sylvatica: the third joint is shorter than the fourth in Lampyris ignita: it is longer than the first in Donacia, many Melolonthidæ, &c. Once more, the fourth joint, usually the shortest of all, is longer than the second and third in Anthia, &c. Lastly, the claw-joint, usually the second in length, in the Eproboscidea Latr. (Hippobosca L.) is very long and large, while the four first joints are so extremely short as to be scarcely distinguishable from each other: it is the shortest of all in Colymbetes, &c.; it is of the length of the third in Cicindela sylvatica, of the fourth in C. sexguttata. Though commonly the slenderest joint of all, particularly so in Raphidia, in many Heteromerous and Lamellicorn beetles it is the largest, conspicuously so in Mellinus tricinctus. Sometimes, as in Buprestis chrysis, &c., all the tarsal joints are nearly equal in length and thickness.

We are next to say something upon the shape of the tarsi and their joints. In general we may first observe that their upper surface is commonly more or less convex, and the lower flat or concave: in insects that are swift runners, as the terrestrial Predaceous beetles, they are usually slender and filiform[2074]; in those that swim, as Dytiscus, the two posterior pair taper nearly to a point from the base to the apex[2075]; in some that climb, as Buprestis, they are rather flat and linear; and in others (the Weevils, Curculio L.) they grow gradually wider towards the claw-joint[2076]; sometimes, as in Mordella Latr., the four anterior tarsi are of this shape, and the posterior pair setaceous. In Gyrinus the four posterior are flat and triangular; and in that extraordinary insect Gryllus monstrosus the tarsi are foliaceous and lobed[2077]. In many males and some others the anterior pair or hands are of a different shape from the two posterior: thus, in several Carabi they are lanceolate; in Staphylinus, Creophilus, &c. in both sexes they are often nearly circular, like those of male Dytisci[2078]. With regard to the shape of individual joints it may be said in general that they are rather triangular, with an anterior sinus for the reception of the succeeding joint: the first joint usually departs most from this form; in the bees it is commonly much larger than the rest, especially in the last pair of legs, and nearly forming a parallelogram[2079]; in Euglossa it is trapezoidal; in the majority nearly linear or filiform. With regard to their termination--in Brachycerus and some ants (Ponera, Myrmica, &c., Latr.) the three first joints; in Dascillus, Lycus reticulatus and affinities, the third and fourth; and in the great majority of the Tetramerous insects the penultimate joint is bilobed; although in most Predaceous beetles this joint is entire or simply emarginate, yet in Colliuris it terminates in a single oblique lobe; and in Lebia, Drypta, &c., it is nearly bipartite. I must now advert to the Ungula or claw-joint: it is usually clavate or thickest at the end and curved; but in the Asilidæ it is shaped like a vase or cup; in Phanæus, in the four posterior tarsi, in which the claws are obsolete, it is thickest at the base and sharpest at the extremity[2080]; it usually forms an angle with the rest of the tarsus, rising upwards, which enables the insect to move more easily without hindrance from the claws, and also more readily to lay hold of any object it meets with; but in the Lamellicorn beetles and many other insects it is in the same line with it. As in the beetles last mentioned this joint is often inserted in the extremity of the preceding one; but in Œdemera it articulates with the middle of its upper surface; and in Lycus and a numerous host of Tetramerous beetles it springs from its base, just behind where it diverges into two lobes.

I shall next call your attention to the different kinds of appendages with which the tarsi are furnished. They are seldom armed, like the tibiæ, with teeth, or spines, or horns; but something of the kind occasionally distinguishes them. In Phileurus, Oryctes, and several other Dynastidæ, the first joint is armed at the apex externally with a considerable mucro; in the fore-leg of Dasytes ater a similar process is prolonged into a crooked horn[2081]. But the most important appendages of the tarsi are the claws which almost universally arm their extremity, and which appear clearly analogous to those of birds, quadrupeds, &c., though probably differing as to their substance[2082]. Some few, however, are without them; this, as I lately observed, is the case with Phanæus with respect to the four posterior legs; the anterior ones of Vanessa amongst the Lepidoptera, and all those of Stylops and many Acari L., are also without them: this is likewise the case with the first pair of legs, or the second of the pedipalps of Galeodes. In this genus these organs consist of two joints[2083]. With respect to number they vary in different tribes, but not so much as the calcaria: these variations may likewise be represented by three numbers. The most natural is two in all the tarsi, exhibited by the Predaceous beetles and the great majority; 2.2.1. are to be found in Hoplia, Anisonyx, &c.[2084]; 1.2.2. in Belostoma; three in all the legs in the Araneidæ[2085]; in Meloe[2086], Elater, &c., each claw is double or consisting of two, which makes four in each leg; and in many Hippoboscidæ there are six[2087]; in Nepa and the Myriapods there is only one. In most insects, perhaps, the claws are simple or undivided[2088]; but in Galeruca, Melolontha subspinosa[2089], &c., they are bifid at the apex; as is the exterior claw of the four posterior legs in Chasmodia and Macraspis[2090] M^cL., and of all in Melolontha horticola; in Serica brunnea M^cL. the claws are all cleft at the extremity, but the internal tooth is broad, flat, and obtuse[2091]; in Melolontha vulgaris and Pelidnota punctata M^cL.[2092], the claws are armed with an internal tooth near the base[2093]. In the Araneidæ, which have three claws, the two external ones are furnished with several parallel teeth, which the animal uses to keep separate the threads of its web, and probably for other purposes[2094]; and some Predaceous beetles, as Lebia and Cymindis, have both their claws similarly furnished[2095]. These organs vary in their relative proportions: thus, in Anoplognathus the inner claw is much smaller than the other[2096]; and in Elater sulcatus, fuscipes, &c., it is represented by a mere bristle; in Hoplia, in the anterior tarsus it is not half the length of the outer one[2097]; in Areoda and Pelidnota M^cL. this last is the smallest. They vary also in length--in Rynchænus, Ascalaphus, &c., they are very short; in the Lamellicorns, Galeodes, &c., very long; and in Myrmeleon longer than the claw-joint. With regard to their curvature they generally form the segment of a circle; in many Asilidæ they are crooked like the claws of the eagle[2098], and the posterior one of the Hopliæ is bent like a hook[2099]; they most commonly diverge from each other; but in the Rutelidæ, Anoplognathidæ, &c., they are perfectly parallel, and in the former often inflexed[2100]. With regard to other appendages of the part we are treating of, if you examine the stag-beetle and many other Lamellicorns, you will find between the claws a minute but conspicuous joint terminated by two bristles which seem to mimic the ungula and its claws; these parts are what are denominated in the table the palmula, plantula, and pseudonychia: in the stag-beetle these are long[2101]; in the Melolonthidæ short[2102]; and in many Cetoniadæ they resemble an intermediate claw.

The most remarkable of the appendages of the tarsi are to be looked for on their under side or sole (solea), and are the means by which numbers of insects can overcome atmospheric pressure and walk against gravity. Many of these have been fully described in a former letter[2103]; but much that relates to them was there omitted, which I shall now detail to you. Four kinds of pulvilli, as I would call these appendages, are found in the sole of insects, upon each of which I shall make a few remarks.

The first is a cushion or brush composed of very thickly set hairs or short bristles: examples of this you will find in the majority of Tetramerous and Trimerous beetles. In Chrysomela, Timarcha, &c., there is one of these cushions on each of the three first joints; in Prionus, Liparus, &c., there is a pair; and in Coccinella on the two first; in others (Balaninus Nucum, &c.) a pair only on the penultimate joint; in Calandra Palmarum, Rhina barbirostris, &c., that joint has an intire cushion; in Eurynotus muricatus K.[2104] the three first joints of the four anterior tarsi are similarly circumstanced, but the cushions resemble sponge[2105].

The second kind of cushion is a vesicular membrane capable of being inflated. This distinguishes the tarsi of Thrips[2106], and many Acari L.[2107]; likewise those of Xenos[2108]; and also of many Orthoptera fully described on a former occasion[2109], though the fact of their capacity of inflation has not been ascertained, belong to this section.

The third kind of covering of the sole is when the three or four first joints of the tarsus each terminate in one or two membranous lobes or appendages: of the first description is Priocera K., in which the lobes are involute[2110]; and of the second Rhipicera Latr.[2111], in which there is a pair on each joint, in the Brazil species set with very fine hairs.

The fourth and last kind are what may with the utmost propriety be denominated suckers, since their use as such is clearly ascertained. These are not only to be found in a large proportion of the Diptera, in some of which there are two of them, as in the Asilidæ[2112]; and in others three, as the Tabanidæ[2113]; but also in many of the subsequent Orders: thus, in the Heteropterous Hemiptera, in Scutellera and Pentatoma, but not the Reduviadæ, and in the Neuropterous genus Nymphes Leach there is a minute one under each claw. It is discoverable between the claws in many Hymenoptera, as Apis[2114], Vespa, &c. But the genus that exhibits to the curious Entomologist the most singular and elaborate apparatus of this kind is Dytiscus Latr.; and the examination of the under side of the hand of any male of this genus will almost compel the most inattentive observer to glorify the wisdom and skill of the ALLFATHER so conspicuously manifested in the structure of these complex organs. For this part in these, instead of two or three pedunculate cups as in the insects just mentioned, is composed of a vast number, some large and some small. If you take a male specimen of the common D. marginalis, you will find that the three first joints of the hand are very much dilated, so as to form a plate or shield nearly circular, fringed all round with stiffish hairs; if you next examine the under side of this plate with a good magnifier, you will discover at the base, where it is united to the cubit, two circular cups, the external one more than three times the size of the other, with an umbilicated centre[2115]; besides these two larger cups the rest of the shield is covered by a vast number of minute ones of a similar construction[2116]: the larger cups are nearly sessile, but the smaller are elevated upon a tubular footstalk[2117]; the three first joints of the intermediate tarsi are also dilated, but not into an orbicular shield, and thickly set with minute pedunculated suckers[2118]. The structure varies however in different species. Thus in D. limbatus the shield is triangular with the smaller suckers at the base, and two rows of larger oblong ones, concave but not umbilicated, at the apex; in another Brazilian undescribed species (D. obovatus K. MS.) the shield is oblong and quite covered with suckers like those last mentioned; in D. sulcatus (Acilius Leach) almost the whole plate is occupied by a very large sucker, above which, at some distance in the inner side, are two smaller ones, while the extremity of the shield is covered by minute ones elevated on long footstalks: the central umbilicated elevation of the large one, which nearly fills its cavity, is in this species beautifully radiated. The male of Colymbetes transversalis has also an orbicular shield, but the suckers are much less strongly marked. The use of this organ has been before sufficiently explained[2119].

A few words will be necessary upon the folding of the legs in repose. When insects walk, the thigh is usually in an ascending position, rising above the horizontal line, the tibia forming with it rather an obtuse angle, and the tarsus nearly a right one with the tibia; but in the Myriapods, as far as I can unravel their swift many-footed motions, these angles in walking do not take place; in repose however, in many insects, the coxa forms an angle with the thigh below the horizontal line and with the tibia above it, and the tibia and tarsus continue in the same line, and point downwards nearly vertically; in others, as in the Tetramerous beetles, the last-mentioned joints form an angle with each other and turn upwards, the tibia having an external oblique cavity to permit this; but the insects most remarkable for packing close their legs are those carnivorous genera Dermestes, Anthrenus, Byrrhus, &c. In the last-mentioned genus there are cavities in the under side of the trunk, in each division of the breast, and at the base of the abdomen, to receive the legs when folded; the coxæ have also a cavity to receive the base of the thigh. In the anterior legs this last part has a longitudinal one on its upper side, and in the four posterior on the under, which receives the tibiæ, which at the inner edge are straight, and at the outer curvilinear, and the tarsi are turned up and received by the concave part, on the anterior side of the first pair and the posterior side of the two last of the tibiæ, so as to lie between it and the body: when the legs are close packed, the animal looks almost as if it had none. I have observed that when Dytisci repose on the water, the posterior legs are turned up and laid over the elytra, and curved towards the head.

vi. Pectines. I must next say a few words upon a remarkable organ, which seems in some degree supplementary to the legs, by which the CREATOR has distinguished the genus Scorpio, called from its parallel teeth, set in a back, their pecten or comb[2120]. This back consists of two or more articulations, is attached by its anterior extremity to the sides of the posterior piece of the mesostethium, and is marked by a longitudinal furrow or channel. The teeth, which vary in number in the different species, and in the same species at different periods of its growth, are usually ovato-lanceolate, or obtusangular, furnished on their exterior edge with what appears to be a longitudinal sucker, and supported between their bases, or at the base, both within and without, by triangular, conical, or subglobose props. With regard to the use of these organs, it has not been clearly ascertained. Amouroux states that he has seen the animals use them as feet, and he conjectures that by them they may fix themselves and turn upon them as on a pivot, when they have to make a retrograde movement[2121]. M. Latreille, from their having branchial pouches immediately under them, seems to think that they are connected with respiration[2122]. This may be true; but from the suckers just described, I am inclined to think with Amouroux, that they are useful to the animal in its motions, and that like the suckers of the Gecko, flies, &c., they enable it to support itself against gravity and to climb perpendicular surfaces.

Whether the five obtriangular plates, elevated on a pedicle, which are found arranged in a series on the under side of each of the jointed coxæ of the posterior legs in Galeodes, are at all analogous to the pectens of scorpions, has not been ascertained[2123]. M. Leon Dufour watched them very attentively in one species (G. intrepidus), but he could observe no motion in them[2124].

FOOTNOTES:

[1585] For the reason which induced the authors to use this word instead of Terminology, before employed, see VOL. I. Pref. p. xii--. They are gratified to see that M. Latreille has adopted this term in the work quoted on the other side, p. 194.

[1586] Organisation Extérieure des Insectes, Mém. du Mus. t. viii.

[1587] Ibid. 199--. I have never been able to procure M. Audoin's Mémoire on this subject.

[1588] Fundament. Entomolog. in Amœn. Acad. vii. 143.

[1589] Terminologie, 1578, &c. He afterwards called the trunk Stethidium: Terminologie der Insekten Magaz. 1806. 14.

[1590] Organisation, &c. 198.

[1591] In Nirmus Anseris, &c. however, in this Order, the same distinction is observable.

[1592] PLATES VIII. & IX. á.

[1593] PLATE VIII. a.

[1594] If the head of any individual of these two Orders be carefully taken off, it will be found that above there is a very short piece representing the prothorax, and quite unlike the collar of Hymenoptera.

[1595] PLATE VIII. FIG. 1.

[1596] Ibid. FIG. 2. a´.

[1597] Ibid. FIG. 1, 10. a.

[1598] Ibid. b.

[1599] Ibid. c.

[1600] Ibid. b.

[1601] Ibid. a.

[1602] See above, p. 327--.

[1603] Coquebert Illustr. Ic. ii. t. xviii. f. 2, 4.

[1604] Stoll Cigales t. xxi. f. 116.

[1605] Ibid. t. xi. f. 53.

[1606] PLATE II. FIG. 4.

[1607] PLATE XIII. FIG. 18. a.

[1608] Stoll Cigales t. xxviii. f. 163.

[1609] Ibid. t. xxi. f. 115. Coquebert Illust. Ic. ii. t. xviii. f. 5.

[1610] Stoll Spectres t. xi. f. 42. t. xii. f. 45. t. xvi. f. 58, 59.

[1611] PLATE IX. FIG. 4.

[1612] Sur le Vol des Ins. c. vii. 374. t. xviii. f. 9. i i.

[1613] PLATE IX. FIG. 5.

[1614] Theatr. Ins. 98.

[1615] De Geer iv. 74.

[1616] Organisation Extérieure des Ins. 177.

[1617] A subgenus, related to Lebia (Hexagonia K. MS.) and some Cimicidæ, are so circumstanced.

[1618] Regne Animal iii. t. xiii. f. 6.

[1619] See above, p. 398.

[1620] PLATE XIII. FIG. 17.

[1621] PLATE VIII. FIG. 10.

[1622] Ibid.

[1623] Linn. Trans. vi. t. xxi. f. 10.

[1624] Ibid. f. 8.

[1625] PLATE VIII. b.

[1626] See above, p. 536.

[1627] Something of the kind is observable at the base of the other legs in this tribe.

[1628] Monro On the Bones, 160.

[1629] PLATE VIII. d´.

[1630] Ibid. FIG. 7. d´.

[1631] Kirby in Linn. Trans. xiv. t. iii. f. 4. i.

[1632] It is doubtful whether M. Latreille's Harpalus megacephalus is synonymous with Carabus megacephalus Fab. Comp. Gen. Crust. et Ins. i. 206. with Syst. Eleuth. i. 187. 95.

[1633] VOL. II. p. 317--.

[1634] PLATE VIII. FIG. 11. b.

[1635] Linn. Trans. iv. 53.

[1636] Syst. Nat. i. Cancer. Scorpio.

[1637] Moses, when he describes insects as going upon four legs, evidently considers the anterior pair as arms; Bochart does the same. Levit. xi. 20--. Hierozoic. ii. 497.

[1638] PLATE XXVII. FIG. 31.

[1639] PLATE XV. FIG. 5, 6.

[1640] Samouelle t. v. f. 4.

[1641] PLATE IX. g.

[1642] Latreille Organization &c., 199. Chabrier Sur le Vol des Ins. c. i. 412. c. iv. 54, &c.

[1643] In Chlorion, Ammophila, &c., this part separates more readily from the alitrunk.

[1644] Chabrier Sur le Vol des Ins. c. i. 413--. c. iv. 54. This author seems to regard the collar as something peculiar to Hymenoptera.

[1645] See above, p. 536.

[1646] PLATE IX. FIG. 11.

[1647] PLATE IX. FIG. 6. a.

[1648] Ibid. FIG. 7. g´.

[1649] M. Chabrier (Vol. des Ins.) supposes that the humming of insects is produced by the exit of the superfluous air from their thoracic spiracles, &c.; in Melolontha he thinks they are in the metathorax under the wings (c. i. 457--. PLATE XXII. FIG. 13. c. †. represents the operculum of one of those of Dytiscus marginalis): in the Hymenoptera, in the mesothorax, near the posterior lobes of the collar (Ibid. 459. c. iv. 50.); and in the Diptera, in the metathorax, near the poiser (c. i. 457). I observed myself lately, that Elophilus tenax, if held by the anterior part of the body, when it hummed, alternately opened and shut this spiracle. The wings during the sound vibrated intensely. The hum ceased and was renewed, as they were restrained from this motion or released from restraint; when the wing was moved towards the head, a different sound was emitted from that produced when it merely vibrated.

[1650] PLATE IX. FIG. 11. g´.

[1651] PLATES VIII. IX. i´.

[1652] When the prothorax is separated from the elytra by a kind of isthmus, as in Scarites, Passalus, &c., the dorsolum is more or less uncovered.

[1653] PLATE VIII. FIG. 16. 20. i´.

[1654] PLATE IX. FIG. 7. i´.

[1655] Ibid. FIG. 10. i´. k´.

[1656] Ibid. FIG. 1. i´. k´.

[1657] Ibid. FIG. 11. i´.

[1658] PLATES VIII. IX. XXVIII. k´.

[1659] Audoin, Chabrier, &c.

[1660] Olivier. He seems also to have thought that neither the Orthoptera nor Homopterous Hemiptera have this part. N. Dict. d'Hist. Nat. x. 112.

[1661] PLATE VIII. FIG. 3. k´.

[1662] In Macraspis MacLeay it is often half as big as an elytrum.

[1663] PLATE VIII. FIG. 12. k´.

[1664] Mr. W. S. MacLeay opposes the Hemiptera to the Orthoptera, the Homoptera to the Neuroptera, and the Aptera to the Coleoptera: but if analogous structure be made the guide, I think my arrangement will be found most correct. Hor. Entomolog. 367.

[1665] PLATE VIII. FIG. 20. k´.

[1666] Ibid. FIG. 16. k´.

[1667] PLATE IX. FIG. 1. k´. N. B. This is from Cossus F.

[1668] PLATE IX. FIG. 7. k´.

[1669] Ibid. FIG. 11, 15. k´.

[1670] Mon. Ap. Angl. i. t. vi. Apis. ** a. f. 2. a a.

[1671] Stoll Cigales t. xxviii. f. 164.

[1672] PLATE IX. FIG. 12. k´.

[1673] PLATES VIII. IX. XXVIII. l'.

[1674] PLATE XXIII. FIG. 6. e´´´.

[1675] PLATE VIII. FIG. 12. l´.

[1676] Ibid. FIG. 20. l´.

[1677] PLATE XXVIII. FIG. 11. l´.

[1678] Chabrier Sur le Vol des Ins. c. iii. t. viii-v. B. i.

[1679] PLATE IX. FIG. 7. m´.

[1680] Chabrier Sur le Vol des Ins. c. iii. 354.

[1681] From πνυμι to breathe and σέγω to cover.

[1682] PLATES VIII. IX. n´.

[1683] At first I had named this piece the antecosta, and the mesostethium the postcosta; and there is certainly some analogy between the thorax of insects, consisting of several pieces that follow each other, and the vertebral column; between their three sternums and the sternum, and between their other pieces and the ribs of vertebrate animals. Comp. Chabrier, ubi supr. c. iv. 49. note 1.

[1684] PLATES VIII. IX. o´.

[1685] PLATE VIII. FIG. 12. 13. o´. z´.

[1686] Ibid. FIG. 17. o´.

[1687] PLATE IX. FIG. 8. o´. z´.

[1688] Ibid. o´.

[1689] PLATE IX. FIG. 8. a.

[1690] Ibid. FIG. 12. o´.

[1691] PLATE VIII. FIG. 3, 13. p´.

[1692] Linn. Trans. xii. t. xxii. f. 4.

[1693] A remarkable instance of analogy is afforded by this genus. In Erotylus there are two groups; one distinguished by gibbous elytra, and the other by flatter ones. The same distinction is observable in Spheniscus; for to this genus belongs Helops fasciatus Oliv., which represents the flat Erotylí, and even individually Erotylus trifasciatus Oliv., E. fasciatus F.

[1694] I would restrict this name to the conical-headed Locustæ F.

[1695] PLATE VIII. IX. t´. Linn. Trans. xi. t. ix. f. 16. c.

[1696] PLATE VIII. FIG. 3. t´.

[1697] Ibid. FIG. 12. Comp. i´, k´, l´, with t´, u´, v´.

[1698] PLATE IX. FIG. 7. t´.

[1699] Ibid. FIG. 11. t´.

[1700] PLATE IX. FIG. 19, 20. t´.

[1701] See above, p. 558--.

[1702] PLATES VIII. IX. u´.

[1703] PLATE VIII. FIG. 3. u´.

[1704] Ibid. VIII. FIG. 12. u´. PLATE IX. 7. u´.

[1705] PLATES VIII. IX. v´.

[1706] PLATE VIII. FIG. 3. v´.

[1707] PLATE VIII. FIG. 12, 16.; and PLATE IX. FIG. 7. v´.

[1708] PLATE VIII. FIG. 3. w´.

[1709] PLATE XXII. FIG. 14. w´.

[1710] PLATE XXIX. FIG. 25. w´.

[1711] Ibid. and PLATE VIII. FIG. 12.; and PLATE IX. FIG. 7. k´´.

[1712] Sur le Vol des Ins. c. iii. 354.

[1713] See above, p. 572.

[1714] PLATE IX. FIG. 15. k´´.

[1715] PLATE IX. FIG. 11. k´´.

[1716] Ibid. FIG. 20. k´´.

[1717] PLATES VIII. IX. y´.

[1718] PLATE VIII. FIG. 4. z´.

[1719] Ibid. p´´.

[1720] Ibid. y´.

[1721] PLATE VIII. FIG. 13. y´. a´ †.

[1722] PLATE XXVII. FIG. 50.

[1723] PLATES VIII. IX. z´.

[1724] PLATE VIII. FIG. 4. z´.

[1725] PLATE XXIX. FIG. 15. z´.

[1726] PLATE IX. FIG. 8. z´.

[1727] PLATES VIII. IX. a †.

[1728] See above, p. 565.

[1729] PLATE VIII. FIG. 8. a †.

[1730] De Geer iv. t. iv. f. 3. d d. c c.

[1731] PLATE VIII. FIG. 13. a †.

[1732] The history of this parasite has been traced by Dr. Reid; but alas! this learned and acute observer of nature did not live to give his discoveries to the world: it is hoped, however, they will not be lost, being in most able hands.

[1733] PLATE VIII. FIG. 18. and XXII. FIG. 13. c †.

[1734] VOL. II. p. 405.

[1735] Sur le Vol des Ins. c. i. 459.

[1736] Ibid. 457--.

[1737] PLATE XXII. FIG. 13. c †.

[1738] Mem. sur les Anim. sans Vertèbr. 45--. Hor. Entomolog. 411--.

[1739] PLATE VIII. FIG. 3. x´. IX. FIG. 2. s´. and XXII. FIG. 5-14.

[1740] PLATE XXII. FIG. 8-11.

[1741] VOL. II. p. 318.

[1742] PLATE XXII. FIG. 8, 11. h´.

[1743] PLATE XXII. FIG. 9, 11. s´.

[1744] Ibid. FIG. 9. a a.

[1745] Ibid. FIG. 11. a.

[1746] Ibid. b.

[1747] PLATE IX. FIG. 2. s´.

[1748] PLATE XXII. FIG. 10, 11. x´. Comp. Linn. Trans. xi. t. ix. f. 16. g.

[1749] PLATE XXII. FIG. 10, 11. d.

[1750] Ibid. FIG. 9. c.

[1751] Ibid. FIG. 10. a.

[1752] Ibid. FIG. 9-11. l´´.

[1753] PLATE XXII. FIG. 5-7.

[1754] Ibid. FIG. 7.

[1755] Ibid. a.

[1756] Ibid. e´.

[1757] See above, VOL. I. p. 191. and II. p. 257, 366.

[1758] This machine is described by Dr. Eschscholtz, Beiträge zur Naturkunde, &c. Heft. i. 24--. t. i. ii.

[1759] PLATE XXII. FIG. 6.

[1760] PLATE XXII. FIG. 6. a.

[1761] Ibid. b.

[1762] Ibid. FIG. 5. b †.

[1763] MacLeay, Horæ Entomolog. 9. Chabrier, Sur le Vol des Ins. c. i. 417.

[1764] PLATE XXII. FIG. 5. b b b.

[1765] Ibid. c.

[1766] Luke xii. 7.

[1767] See above, p. 397--.

[1768] See above, p. 580.

[1769] Chabrier Sur le Vol des Ins. c. i. 413--.

[1770] See above, p. 402.

[1771] Chabrier Sur le Vol des Ins. c. i. 446, 448, 451--.

[1772] Ibid. 412.

[1773] Ubi supr. c. ii. 333.

[1774] According to M. Chabrier, who agrees with him, M. Latreille also is of opinion, that the parapleura is the analogue of the posterior coxæ. Ubi supra, c. ii. 312. Note 2.

[1775] M. Latreille has changed the denomination of this Order to Rhiphiptera, because at first he thought that these organs were not at all analogous to elytra or wings; but since, upon further investigation, he appears to admit that they assist in flight (Annales Génér. des Scienc. Phys. VI. xviii. 8. Compare MacLeay, Hor. Entom. 423. Note *), in common justice he is bound to restore the name originally given to the Order. In the same place of the work here quoted, M. Latreille also speaks of these pseudelytra, as I would call them, as appendages of the mesothorax: but whoever consults Mr. Bauer's admirable figures of Xenos Peckii (Linn. Trans. xi. t. ix.), and is aware of the unimpeached and minute accuracy of that admirable microscopic artist, will be convinced that they belong to the anterior legs, and consequently to the prothorax.

[1776] PLATE X. and PLATE XXVIII. FIG. 18-23.

[1777] Chabrier, Analyse, &c. 27.

[1778] N. Dict. d'Hist. Nat. ix. 568. We have seen above (p. 578.) that the wings of insects are connected with their legs by the scapula and parapleura.

[1779] MacLeay, Hor. Entomolog. 413--. Mr. MacLeay's opinion seems to receive some confirmation from a circumstance overlooked when the larvæ of insects were treated of above (p. 130--), and to which he alludes (411); namely, that in that state they consist of two segments more than in the imago; these follow the three pedigerous segments, have no pro-legs, and are supposed to belong to the trunk rather than to the abdomen. To make this circumstance bear upon the question, it must be proved that in the perfect insect these segments in some manner become the back of the trunk and bear the wings. This would not be more wonderful than many changes that are known to occur in insects.

[1780] Latreille, Organization extérieure des Ins. 173--.

[1781] For instance Meloe, the female glow-worm, Lygæus brevipennis, Ephemera diptera, Cynips aptera, neuter ants, &c. &c.

[1782] See above, p. 559.

[1783] Chionea araneoïdes Dolm.

[1784] See above, p. 560, and VOL. II. 348, 352--.

[1785] See above, p. 591, Note c.

[1786] De Geer, iii. t. xvii. f. 10, 11. f f. M. Savigny has noticed a part in some Annelides, which he regards as analogous to elytra. Système des Annelides, 4, 9, 11.

[1787] VOL. II. p. 346--.

[1788] PLATES X. and XXVIII. b^..

[1789] Ibid. c^..

[1790] Ibid. d^..

[1791] PLATE XXVIII. FIG. 3-5. b´´´.

[1792] Chabrier Sur le Vol des Ins. c. i. 439.

[1793] PLATE XXVIII. FIG. 10.

[1794] Chabrier ubi supr.

[1795] PLATE XXVIII. FIG. 6-8. d´´´.

[1796] Ibid. FIG. 3-5. b´´´.

[1797] PLATE XXVIII. FIG. 3.

[1798] PLATE X. FIG. 1. c´´´.

[1799] PLATE X. FIG. 1. c.

[1800] PLATE XXVIII. FIG. 6-8. d´´´.

[1801] PLATE XXVIII. FIG. 8.

[1802] See above, p. 582.

[1803] See above, p. 402--.

[1804] Ibid. 399.

[1805] Sur le Vol des Ins. i. c. 428--. c. ii. 325.

[1806] Oliv. Ins. No. 97. Cassida, t. i. f. 10.

[1807] See above, p. 397--.

[1808] See above, p. 399--.

[1809] M. Chabrier says that the arc described by the wings of Melolontha vulgaris to that of the elytra, is as 200 to less than 50. Sur le Vol des Ins. c. i. 440.

[1810] PLATE X. FIG. 2. and XXVIII. FIG. 18-20.

[1811] Magas. 1806. Terminologie der Insekt. 18. 1675.

[1812] PLATE X. FIG. 2. is the tegmen of a Blatta divided into areas.

[1813] Sur le Vol des Ins. c. ii. 327--.

[1814] PLATE X. FIG. 2. b^..

[1815] Ibid. c^..

[1816] Ibid. d^..

[1817] Stoll, Cigales, t. viii. f. 39.

[1818] PLATE X. FIG. 2.

[1819] Stoll Grillons t. i. c. f. 2.

[1820] Ibid. Spectres t. xxv. f. 95. and xi. f. 42.

[1821] Ibid. t. ii. f. 5. Grillons t. i. c. f. 1.

[1822] Ibid. Spectres t. xvi. f. 58.

[1823] Ibid. Sauterelles à Sabr. t. iii. f. 7. By this name (Pterophylla) I distinguish those Locustæ F. without a conical head that are veined like leaves.

[1824] Stoll Ibid. t. vi. a. f. 18. and PLATE XXVIII. FIG. 19.

[1825] Stoll Sauterel. à Sabr. t. i-iii.

[1826] Ibid. Spectres t. iv. f. 14.

[1827] Ibid. Cigales t. i. f. 1, 3-5. and t. vi. f. 31.

[1828] Stoll Cigales t. iii. f. 12-15. and t. xvii. f. 92.

[1829] Linn. Trans. xii. 449, no. 96.

[1830] VOL. I. p. 395--.

[1831] Linn. Trans. xiii. t. i. f. 14. Flata should come before this genus.

[1832] Of this kind is one of Stoll's Cigales, t. xxv. f. 141.

[1833] PLATE XXVIII. FIG. 18.

[1834] Stoll Cigales t. i. f. 1. t. x. f. 46. t. xxix. f. 170. t. v. f. 22. t. iv. f. 19. &c.

[1835] PLATE X. FIG. 3.

[1836] In Latreille's whole genus Pentatoma, including several Fabrician genera, the Hemelytra are more substantial than in the subsequent tribes.

[1837] See above, p. 607.

[1838] Ibid. p. 600.

[1839] My insect, which nearly resembles the Coleopterous genus Cerylon Latr., agrees with Latreille's description in all respects, except that it cannot be said to be membrana nulla apicali.

[1840] Chabrier Analyse, &c. 24.

[1841] PLATE X. FIG. 3. b^..

[1842] Ibid. c^..

[1843] Ibid. d^..

[1844] PLATE XXVIII. FIG. 23. f´´´ is the corium and g´´´ the membrana of a species of Reduvius F.

[1845] PLATE XXVIII. FIG. 23.

[1846] Chabrier Analyse, &c. 23.

[1847] Chabrier Sur le Vol des Ins. c. ii. 325--. and 326. Note 1.

[1848] See above, p. 572--.

[1849] PLATE XXVIII. FIG. 9. a.

[1850] See above, p. 572.

[1851] Ibid. p. 560. and PLATE XXVIII. FIG. 11. a.

[1852] PLATE IX. FIG. 5.

[1853] Ibid. FIG. 11. 12. g´´.

[1854] Stoll Sauterelles à Sabr. t. iv. f. 12. t. vi. f. 21. &c.

[1855] Sur le Vol. des Ins. c. i. 424.

[1856] The idea of dividing the wing of an insect into larger areas seems first to have been acted upon in Monogr. Apum Angl. (1801), in which those of Hymenoptera were stated to consist of three portions, viz. Basis, Medium, Apex (i. 211.); which mode of dividing them was at first adopted by M. Latreille (Gen. Crust. et Ins. iii. 226. Note 1.) The same learned author (Ibid. iv. 239.), with regard to the Diptera, made a near approximation to the plan of dividing wings into longitudinal areas, but by the addition of a basal area, which interrupts the attention to the communication of the areas with their axes, he has rendered his system less perfect. Two of his terms--Costal Area and Intermediate Area, are here adopted; but his Internal is changed to the Anal Area, for the term internal belongs rather to the base of the wing. M. Latreille afterwards relinquished both these plans, N. Dict. d'Hist. Nat. i. 248--.

[1857] PLATE X. and XXVIII. b^.. i^.. is the Postcostal Nervure.

[1858] Ibid. c^.. n^.. is the Anal Nervure.

[1859] Ibid. d^..

[1860] PLATE X. FIG. 7. h^.. i^.. k^..

[1861] Ibid. FIG. 8. 9. 12. a *.

[1862] Sur le Vol. des Ins. c. i. 428.

[1863] See above, p. 600. 616.

[1864] VOL. II. p. 358--. See above, p. 559.

[1865] VOL. II. p. 346--.

[1866] Jurine Hymenopt. 19. and t. v.

[1867] PLATE X. FIG. 4.

[1868] N. Dict. d'Hist. Nat. i. 251.

[1869] See above, p. 564, 578, 591.

[1870] PLATE X. h^..

[1871] Ibid. FIG. 4, 11. m´´´.

[1872] PLATE X. FIG. 14. k^..

[1873] Ibid. FIG. 12. k^..

[1874] Ibid. FIG. 8. 9.

[1875] Jurine Hymenopt. t. v. Gen. 47.

[1876] PLATE X. FIG. 4.

[1877] Ibid. a. n^., o^..

[1878] Ibid. m^..

[1879] Ibid. l^..

[1880] Ibid. a.

[1881] Ibid. o´´´.

[1882] PLATE II. FIG. 1. Comp. Linn. Trans. xi. t. ix. f. 1.

[1883] PLATE X. FIG. 5.

[1884] Ibid. n^., o^., p^..

[1885] Stoll Spectres, t. xviii. f. 65.

[1886] See above, p. 624.

[1887] Stoll figures Empusa as without them, t. ix. f. 35. but? I have a nondesc. Phasma? without them.

[1888] Jones in Linn. Trans. ii. t. viii. f. 2.

[1889] Ibid. f. 5.

[1890] Jones in Linn. Trans. ii. t. viii. f. 7.

[1891] Ibid. f. 9.

[1892] Ibid. f. 2, 3, 6-9.

[1893] I wonder Mr. Jones's plan of ascertaining the divisions or subgenera of butterflies by the neuration of their wings has never been followed up; it would I think furnish an easy clue for the extrication of the tribes of all the Lepidoptera. I mean as subsidiary to more important characters.

[1894] PLATE X. FIG. 6. l^., m^..

[1895] Ibid. FIG. 8.

[1896] PLATE X. FIG. 8. basal e^., medial f^., apical g^..

[1897] Jurine Hymenopt. t. v. Gen. 48.

[1898] Ibid. Gen. 47.

[1899] Ibid. Gen. 45, 46. Comp. PLATE X. FIG. 11.

[1900] Jurine Ibid. Gen. 43.

[1901] Ibid. t. iv. Gen. 47.

[1902] Ibid. t. v. Gen. 40.

[1903] Ibid. t. ii. Gen. 2.

[1904] This is a remarkable insect belonging to Vespa L., related to the hornets (V. Crabro), distinguished by having a semicircular piece taken out of the internal margin of each mandible, so that when these organs are closed there is a circular orifice,--whence the name Cyclostoma.

[1905] Jurine Hymenopt. t. ii. Gen. 2.

[1906] Ibid. Ord. ii. Gen. 2.

[1907] Ibid. t. iii. Gen. 3.

[1908] Ibid. t. v. Gen. 41.

[1909] Ibid. t. xii. Gen. 40.

[1910] Ibid. t. v. Gen. 39.

[1911] Ibid. t. iv. Gen. 29.

[1912] Ibid. t. v. Gen. 42.

[1913] This Cynips inhabits a long polythalamous gall of the bramble.

[1914] Jurine Ibid. t. ii. Gen. 11.

[1915] Ibid. Ord. ii. Gen. 1.

[1916] Ibid. t. iv. Gen. 23.

[1917] Ibid. Gen. 30-32.

[1918] Ibid. t. v. Gen. 40.

[1919] PLATE X. FIG. 12, 15. c^..

[1920] Ibid. FIG. 15. f^..

[1921] Ibid. FIG. 12. g^..

[1922] Ibid. FIG. 13.

[1923] Ibid. FIG. 15. c.

[1924] Ibid. d.

[1925] Ibid. FIG. 14. e.

[1926] Leach on Eproboscideous Insects, Mem. Wern. Soc. 1817. t. xxv. f. 3, 5, 8, &c.

[1927] Ibid. t. xxvi. f. 7, 10, 13.

[1928] Insects with short elytra of course must fold their wings nearer the base than those with long ones.

[1929] PLATE X. FIG. 4. o´´´.

[1930] See above, p. 611.

[1931] See above, p. 613, and Chabrier Analyse, &c. 24.

[1932] PLATE XXIII. FIG. 5.

[1933] PLATE X. FIG. 5.

[1934] PLATE XXVIII. FIG. 22.

[1935] See above, p. 608--.

[1936] Stoll Grillons, t. iii. c. f. 11-13.

[1937] Ibid. t. i. c. f. 1, 2.

[1938] See above, p. 636.

[1939] See above, p. 625.

[1940] Ibid. p. 635, 637. &c.

[1941] PLATE X. FIG. 4, 5. and XXVIII. FIG. 21, 22.

[1942] PLATE X. FIG. 6-14.

[1943] Ibid. FIG. 4, 5. and XXVIII. FIG. 21, 22.

[1944] PLATE X. FIG. 4.

[1945] Ibid. FIG. 5.

[1946] PLATE X. FIG. 6.

[1947] Ibid. FIG. 8-11.

[1948] Ibid. FIG. 12-15.

[1949] PLATE XIV. FIG. 4.

[1950] Ibid. FIG. 2.

[1951] In Gastropacha quercifolia, &c., amongst the Nocturnal Lepidoptera, these sinuses exist, in the upper wing ten, and in the lower nine, but without the folds.

[1952] PLATE XIV. FIG. 1. s.

[1953] Ibid. FIG. 3.

[1954] For some uses of hairs, see above. p. 399--.

[1955] Analyse, 24. He seems to think that certain crooked hairs, in some wings, supply the place of folds. Ibid.

[1956] PLATE X. FIG. 13.

[1957] Reaum. iv. t. xxxix. f. 4-11.

[1958] A portion of the antenna of the insect here mentioned is figured PLATE XII. FIG. 23.

[1959] De Geer i. 63--.

[1960] Reaum. i. 200.

[1961] Hoole's Leeuwenhoek. i. 63--.

[1962] De Geer has given 34 figures of different scales (i. t. iii. f. 28); and in PLATE XXII. FIG. 6. a-w. 22 others, collected from Reaumur, are given.

[1963] Stoll Sauterelles à Sabre. Pterophylla ocellata t. i. ii., Cigales, Fulgora laternaria t. i. f. i., and F. serrata t. xxix. f. 170.

[1964] Ibid. Sauter. de Passage, Locusta Dux t. i. 5. L. carinata t. v. b. f. 16. L. cristata t. ix. b. f. 30. &c. &c.

[1965] PLATE XXV. FIG. 30.

[1966] Scopoli, Hubner.

[1967] PLATE III. FIG. 1.

[1968] N. Dict. d'Hist. Nat. viii. 257.

[1969] See above, p. 303.

[1970] Sepp. I. i. t. vii. f. 6.

[1971] Rœmer Genera t. xxii. f. 2.

[1972] Sepp I. iii. t. ii. f. 7.

[1973] Ibid. i. t. vi. f. 7.

[1974] Rœmer ubi supr. t. xiv. f. 1.

[1975] PLATES f^., r^., d†.

[1976] See above, p. 546--.

[1977] Ibid. 131--.

[1978] VOL. II. p. 307.

[1979] De Geer i. t. xx. f. 11.

[1980] Règne Animal. iii. 546.

[1981] PLATE XXVII. FIG. 44, 45.

[1982] VOL. II. p. 312, 363, 365.

[1983] See above, p. 546--.

[1984] Anatom. Compar. i. 453.

[1985] See above, p. 308.

[1986] PLATE XXVII. FIG. 18, 19.

[1987] Mr. Montague describes the legs of Nycteribia, as dorsal (Linn. Trans. xi. 13); but Dr. Leach calls them lateral (Samouelle, 303).

[1988] N. Dict. d'Hist. Nat. xxviii. 247.

[1989] PLATE XXIII. FIG. 4.

[1990] PLATE XXVII. FIG. 58. M. Savigny affirms that these insects cannot have, and really have not, but one pair to each segment; only that the segments are alternately membranous and shelly, and that the former are concealed under the latter (Anim. sans Vertebr. I. i. 44.): but, pace tanti viri, I cannot discover that any suture separates these portions from each other: so that, admitting his theory, they must be regarded as two segments soldered together.

[1991] It is by this arrangement of the legs that Pachysoma is principally distinguished, as a subgenus, from Scarabæus M^cL.

[1992] See above, p. 37.

[1993] Monogr. Ap. Angl. i. t. xi. Apis **. d. 2. α. f. 18. ii. 296--.

[1994] Oliv. Ins. 68. t. i. f. 8.

[1995] Ibid. n. 6. t. iv. f. 22.

[1996] See above, p. 305--.

[1997] This variety appears to differ very little from the Curculio imperialis of Fabricius and Olivier, except in the remarkable hairiness of its legs.

[1998] VOL. II. p. 563.

[1999] Oliv. Ins. n. 67. t. xx. f. 156.

[2000] See above, p. 591. Some physiologists have been of opinion, that in birds, what is called the thigh should properly be denominated the tibia, and that this last is really the tarsus. Illiger, Terminologie, 184. § 185. n. 1246.

[2001] PLATES XIV. XV. XXVII. p.

[2002] PLATE XV. FIG. 1. p´´, r´´.

[2003] PLATE XXVII. FIG. 27.

[2004] L. Dufour, Descr. des six Arachn. &c.: Annales Generales, &c. 1820. 19. t. lxix. f. 7. d.

[2005] PLATE XIV. XV. XXVII. q´´.

[2006] N. Dict. d'Hist. Nat. xvi. 195. xxvi. 157.

[2007] PLATE XXVII. FIG. 12. b.

[2008] PLATE XXVII. FIG. 20. q´´.

[2009] Ibid. FIG. 28.

[2010] PLATE XIV. XV. XXVII. r´´.

[2011] See above, p. 591, 662.

[2012] VOL. II. p. 314--.

[2013] Linn. Trans. xii. t. xxi. f. 12.

[2014] Stoll Spectres t. xvi. f. 58, 59.

[2015] Ibid. t. xviii. f. 65.

[2016] Stoll Spectres t. vii. f. 25.

[2017] Ibid. t. viii. f. 30.

[2018] Ibid. ubi supr.

[2019] Ibid. t. x. f. 40.

[2020] PLATE XIV. FIG. 5. This appearance of scales on the thighs is principally confined to this tribe.

[2021] PLATE XXVII. FIG. 23.

[2022] Linn. Trans. xii. t. xxii. f. 16.

[2023] PLATE XIV. FIG. 5, and XXVII. FIG. 15. r´´´.

[2024] PLATES XIV. XV. XXVII. s´´.

[2025] PLATE XXVII. FIG. 21. s´´´. M. Savigny (Anim. sans Vertèbr. 1. i. 46. Note b.) seems to think that this structure obtains in all his Apiropods; viz. the Octopod Aptera, Arachnida, and Myriapoda: but it seems to me evident only in the two tribes mentioned in the text.

[2026] PLATE XXVII. FIG. 6, 16, 17. t´´´.

[2027] PLATE XXVII. FIG. 15. r´´´.

[2028] Ibid. FIG. 11. r´´´.

[2029] Ibid. FIG. 10. t´´´.

[2030] PLATE XXVII. FIG. 8. Thigh. a. Protuberance. b. Semicircular cavity, c. Ridge. FIG. 9. Tibia. a. Central cavity. b. Ridge. c. Exterior cavity.

[2031] Ibid. FIG. 6. a.

[2032] Ibid. FIG. 7. a.

[2033] Ibid. FIG. 15. Thigh of Locusta Leach, a. Sinus in which the condyle of the tibia works. FIG. 16. Tibia of Do. aa. Lateral condyles. b. Intermediate one.

[2034] Stoll Punaises, t. x. f. 67. t. xvi. f. 114.

[2035] Stoll Punaises, t. ii. f. 14. t. viii. f. 54. t. xxviii. f. 201. PLATE XV. FIG. 2.

[2036] See above, p. 671.

[2037] Oliv. Ins. n. 66. t. iii. f. 12. Compare Scarabæus longimanus, Ibid n. 3. t. iv. f. 27.

[2038] Stoll Punaises, t. iii. f. 20.

[2039] PLATE XXVII. FIG. 31.

[2040] See above, p. 306--.

[2041] Oliv. Ins. n. 68. t. i. f. 8. comp. n. 67. t. xii. f. 83. and PLATE XII. FIG. 25. a.

[2042] VOL. II. p. 365. and PLATE XV. FIG. 5. 6.

[2043] See above, p. 433, Note b. and 404, Note a.

[2044] PLATE XIV. FIG. 5.

[2045] It is remarkable that in this tribe all the legs may be called raptorious, though the thighs are not incrassated, for they are armed with a double series or more of fine long spurs, which enable them to catch and retain their prey.

[2046] PLATE XXVII. FIG. 35. v´´´. Philos. Trans. 1816. t. xix. f. 8, 9. See above, VOL. II. p. 331.

[2047] See above, p. 591, 667, &c.

[2048] Règne Animal, iii. 191. I have never had an opportunity to consult Bonelli's Observ. Entomolog. on the genus Carabus L. in the Memoirs of the Turin Academy.

[2049] PLATE XV. FIG. 6. v´´´.

[2050] Coquebert Illustr. Ic. iii. t. xxi. f. 3. D.

[2051] PLATE XXVII. FIG. 29. v´´´.

[2052] Most of Latreille's genera of ants are confirmed by differences in their spurs. Thus Formica is 1:1:1; Ponera 1:2:2 with the internal intermediate one pectinated: Myrmica 1:2:2 with all symmetrical, &c.

[2053] PLATE XXVII. FIG. 29. v´´´.

[2054] Ibid. FIG. 33. v´´´.

[2055] Linn. Trans. iv. 200. Note a.

[2056] PLATE XXVII. FIG. 32. v´´´.

[2057] Ibid. FIG. 36. a^..

[2058] PLATES XIV. XV. XXVI. XXVII. a´´, t´´.

[2059] PLATE XXVI. FIG. 44, 46, 47. a.

[2060] By Geoffroy--Hist. Ins. i. 58.

[2061] The Cleridæ, which M. Latreille has placed in the pentamerous section, vary considerably in the number of their tarsal joints. Thus in general in Thanasimus the tarsi are pentamerous; but in T. formicarius they appear to be heteromerous; and in Enoplium, Opilo, Clerus and Necrobia they are tetramerous. M. Latreille's expression, (N. Dict. d'Hist. Nat. vii. 172.) "le premier article etant fort court et caché sous le second," seems to indicate that there is a fifth joint in some of these, the first being concealed under the second; but I have never been able to discover it. Perhaps he reckoned the pulvillus as a joint?

[2062] The term heteromerous properly belongs to all insects in which the different pairs of tarsi vary inter se in the number of their joints, and it is here used in that large sense.

[2063] These three genera appear really to have only six legs, since the pedipalps or maxillary legs are not armed with claws, while the real representatives of the legs, or three last pair, are so distinguished. In Phrynus and Thelyphona the anterior pair are chelate; but in Galeodes they are pediform, as in the Araneidæ, and the great chelæ are the mandibles.

[2064] PLATE XXVI. FIG. 47, 48. d *.

[2065] PLATE XXVI. FIG. 49. s^.. a.

[2066] VOL. II. p. 330.

[2067] Dr. Leach says there are three joints in this tribe. Nat. Misc. iii. 80.

[2068] From De Geer's description this insect seems related to Agathidium (iv. 221--. t. viii. f. 21-23). M. Leclerck de Laval discovered it to be monomerous. Règne Animal, iii. 365.

[2069] PLATE XXVII. FIG. 22.

[2070] See above, p. 311. Note a.

[2071] Melolontha sericea and aurulenta. Linn. Trans. xii. 463. 400. belong to this subgenus.

[2072] See above, p. 335--.

[2073] PLATE XXVII. FIG. 25.

[2074] PLATE XIV. FIG. 7. t´´.

[2075] Ibid. FIG. 6. t´´.

[2076] PLATE XXVI. FIG. 47.

[2077] PLATE XXVII. FIG. 41.

[2078] PLATE XV. FIG. 9.

[2079] Mon. Ap. Angl. i. t. xii. neut. f. 20.

[2080] PLATE XXVII. FIG. 44. s^..

[2081] PLATE XXVII. FIG. 26. w´´´.

[2082] See above, p. 396.

[2083] L. Dufour Descr. de six Arachnides. Annales, &c. 1820. 19.

[2084] PLATE XXVII. FIG. 51. is the posterior claw of Hoplia.

[2085] PLATE XXIII. FIG. 14.

[2086] PLATE XXVII. FIG. 52.

[2087] Ibid. FIG. 46.

[2088] Ibid. FIG. 53, 54.

[2089] Ibid. FIG. 49.

[2090] Ibid. FIG. 38.

[2091] Ibid. FIG. 39.

[2092] This structure is not general in this genus.

[2093] PLATE XXVII. FIG. 40.

[2094] PLATE XXIII. FIG. 14.

[2095] PLATE XXVII. FIG. 43.

[2096] Ibid. FIG. 47.

[2097] Ibid. FIG. 48.

[2098] PLATE XXVII. FIG. 53.

[2099] Ibid. FIG. 51.

[2100] Ibid. FIG. 47.

[2101] Ibid. FIG. 56. _a_ψ, f*.

[2102] Ibid. FIG. 49. _a_ψ, f*.

[2103] VOL. II. p. 326--.

[2104] Linn. Trans. xii. t. xxii. f. 1.

[2105] For other instances of this structure, see above, p. 336.

[2106] De Geer, iii. 7.

[2107] Ibid. vii. 84. PLATE XXVII. FIG. 60, 63.

[2108] Ibid. FIG. 61.

[2109] VOL. II. p. 327--.

[2110] PLATE XXVII. FIG. 59.

[2111] Linn. Trans. xii. t. xxi. f. 3.

[2112] PLATE XXVII. FIG. 53.

[2113] PLATE XXVII. FIG. 54. Philos. Trans. 1816. t. xviii. f. 9-11.

[2114] PLATE XXVII. FIG. 55. t.

[2115] PLATE XV. FIG. 9. a.

[2116] Ibid. b.

[2117] Philos. Trans. 1816. t. xx. f. 9, 12-15.

[2118] Philos. Trans. 1816. t. xx. f. 4, 11.

[2119] See above, p. 305--.

[2120] PLATE XXVII. FIG. 50.

[2121] Amouroux Insectes Venimeux, 44.

[2122] Observations Nouvelles, &c. Mém. du Mus. viii. 177.

[2123] N. Dict. d'Hist. Nat. xii. 370.

[2124] Descr. de six Arachnides, &c. Annales Gen. des Scienc. Phys. 1820. 19. t. lxix. f. 7. d.