XXXIV. EXTERNAL ANATOMY OF INSECTS

XXXIV. EXTERNAL ANATOMY OF INSECTS

THE HEAD, AND ITS PARTS.

Before I confine my observations to the head of insects, which I propose to consider separately in the present letter, I must premise a few words upon their body in general, or rather its crust, or external integument. In this we may notice its substance, general form, sculpture, pubescence, and composition.

i. I have already noticed the substance of this integument in the preparatory states of insects[1151]; I shall not, therefore, here repeat what I then said, but restrict myself chiefly to the consideration of it as it is found in their last state, in which it is usually firmer than in their previous stages of existence. In this respect, however, it varies much in the different Orders, and even in the different genera of the same Order. In some Coleopterous insects, for instance, it is very hard, and difficult to perforate; while in others it is soft, flexible, and a pin easily passes through it[1152]. And in general, from a substance in hardness resembling horn or shell, it passes through the intermediate degrees of that of leather and parchment, almost to a thin membrane. Yet in all cases there is enough of rigidity and hardness to answer the principal uses of a skeleton--to afford, namely, a sufficient point of attachment for the muscles, and to support and defend the interior organization; so that the play and action of the vital and secretory systems may not be interrupted or impeded.

With respect to the principles which enter into the composition of this integument, very little seems to be known at present; but few insects having been submitted to a chemical analysis. The blister-beetle (Cantharis vesicatoria), from its importance in medicine, has, however, been more than once analysed; and though the products have not been very precisely stated, yet we find amongst them phosphate of lime, albumen, and some other usual components of the substance of vertebrate animals[1153]. But which of these products belong to the integument, and which to its contents, cannot be ascertained, without a separate process for each; which would not, I conceive, be very feasible. The substance, however, of the integument of insects, though we know not its precise contents, which probably vary in different genera, &c., appears not to be exactly of the nature of any of those substances after which it has usually been denominated: it is not properly analogous either to real horn, shell, skin, or leather, &c. This seems to result from the following circumstance:--Most of the excretions of vertebrate animals, as horn, skin (at least when tanned), feathers, wool, hair, &c. when exposed to the action of fire liquify, more or less, before they incinerate; emitting at the same time a peculiar and disagreeable scent: but upon applying this test to the parts of insects of the different Orders, I found, in every instance, that incineration took place without liquefaction, and was unaccompanied by that peculiar scent which distinguishes the others. Even the claws, which to the eye appear, as to their substance, exactly like those of Mammalia, birds, &c. burn without melting, and retain their form after red heat. That the insect integument is not calcareous like that of the Crustacea, and the shells of Molluscæ, you may easily satisfy yourself, by immersing them in an acid test. I made this experiment upon portions of insects of several of the Orders, in an equal mixture of muriatic acid and water, and the result was, not only that all hexapods, but octopods, Arachnida, and even Scolopendridæ, upon immersion only emitted a few air-bubbles; while, when the other myriapods, Polydesmus, Iulus, Glomeris, &c. and the Oniscidæ, were immersed, a violent effervescence took place; proving the different nature of their substance. It is remarkable that the two great branches of the Myriapods, the Scolopendridæ and Iulidæ (Chilopoda and Chilognatha Latr.), should in this respect be so differently circumstanced--the latter having a calcareous integument, and the former not.--A further difference distinguishes these two tribes: old specimens of the Iulidæ usually lose their colour and turn white, like Oniscidæ; while those of the Scolopendridæ retain it.

ii. The form of insects is so variable, that it can be reduced to no other general rules--than that, for the most part, the length exceeds the breadth, and the breadth the depth, and that the upper surface is usually convex. But to these rules there are numerous exceptions. Thus many Tetyræ F. (Scutellera Latr.), a kind of bug, are as broad as they are long[1154]; in the genus Gonyleptes K.[1155] amongst the Aptera, and Epeira cancriformis, a crab-shaped spider, the breadth exceeds the length; in Cynips, and several other Hymenoptera, in Acrida K.[1156] (Locusta F.), and other Orthopterous insects, the depth exceeds the breadth; and in that singular beetle, Eurychora; the cockroach (Blatta), &c. the upper surface is flat.

iii. The sculpture of the integument of insects is often very remarkable; but as this will call for attention hereafter, I shall only here observe in general, that ornament and variety seem not to be the sole object of those elevations and depressions which form so prominent a feature of many of the animals in question; for by means of these, many important purposes, that at first sight do not strike the observer, may be served: such as giving firmness to the crust in those places where it is most wanted; diminishing its powers of resistance in others, so that it may yield somewhat to the action of the muscles; increasing or deducting from the weight of the body, so as to produce a proper equipoise during its motions, whether on the earth, in the air, or in the water. The depressions of the outer surface of the crust, in many instances, produce an elevation of it in the interior, and so afford a useful point of attachment to certain muscles. This observation seems more especially applicable to those excavations that are common to particular tribes or genera: thus the dorsal longitudinal channel to be met with on the prothorax of most of the Carabi of Linné on the inside of the crust have a corresponding ridge. In Locusta Dux, also, (a Brazil locust,) the same part has four transverse channels, corresponding with which on the inside are as many septa, or ridges, to which muscles are attached; and those larger impressed puncta denominated puncta ordinaria, which distinguish the same part in Geotrupes and many of the Scarabæidæ, within are elevated, so as to form a kind of ginglymous articulation with the base of the anterior coxæ. The other impressed puncta so often to be seen on the different parts of various insects, which sometimes so intirely cover the surface that scarcely any interval is discoverable between them, though in many cases they appear to be mere impressions that attenuate but do not perforate the crust--yet in others, perhaps equally or more numerous, they are real pores, which pass through the integument. If, for instance, you take the thoracic shield of the cockchafer (Melolontha vulgaris), and after removing the muscle &c., hold it against the light, with the inner side towards the eye, you will see the light through every puncture: or take the elytra of Geotrupes stercorarius, or any common beetle in which these organs have punctate striæ, and examine them under a lens on the inside, and you will see distinctly that the punctures pass through the elytrum, and the membrane that lines it[1157]. It is not improbable that in the case last mentioned these pores may be of use, as the spiracles are usually closely covered by the elytra, for the better transmission of the air to those respiratory organs. Whether the pores in the other parts of the body are for transpiration, is more than I shall venture to affirm; but as insects sometimes perspire, at least this has been ascertained with respect to the hive-bee[1158], this must be by the means of some pores.

iv. The integument of insects is often clothed, either partially or generally, with pubescence, or hairs of various kinds--a circumstance which seems to have more than one object. In Parnus, Heterocerus, Gerris, Argyroneta aquatica, and some other aquatic insects, the end in view seems to be to keep the water from wetting the crust; and in this case the covering of hairs is dense, silky, and decumbent. Another object is preventing friction from being injurious: thus humble-bees, that from their mode of nidification[1159], are usually more particularly exposed to it, are well clothed with hair; and in those articulations of insects where much friction takes place, we may often observe a dense fringe or coating of the same substance. This you may see in the common stag-beetle (Lucanus Cervus), where the thorax receives the head; and very remarkably at the same point in the Hercules-beetle (Dynastes Hercules MacLeay): but besides these uses, there is probably one more universal, which will apply as well to those thinly scattered bristles and hairs, here and there one, to be noticed in many insects: but concerning this I can only throw out a conjecture, as I do not recollect ever to have seen any experiments with regard to this use of animal hairs. But may they not act as conductors, either to introduce some invisible fluid into the body in a positive state, or to convey it out, when received by other means, in a negative state? Every one knows that the fur of a cat has electric properties, and there may be an important general use of this kind attached to the fur and hairs of animals[1160]. But, as I said, I give this as a mere conjecture; and only wish it may excite your attention to the subject, and put in exercise your natural tact for experiment.

M. Cuvier regards the hairs of insects as merely a continuation of the epidermis, with which they fall when the animal changes its skin[1161]; but this will apply only to the hairs of larvæ: for the hairs of perfect insects in many cases are implanted in a pore, and pass through epidermis or crust to the membrane that lines it, in which they terminate.

v. We are now to consider the composition of the integument; under which term I would include the different layers of which it consists, and its articulation.

1. With respect to the first of these circumstances, the layers of which the integument consists, it seems to exhibit some, although not an exact, analogy with the skin, rather than the skeleton, of the vertebrate animals[1162]. In these last, the skin is stated to consist of four layers. Of these the exterior one is the epidermis, or scarf-skin: under this is the rete mucosum, or mucous tissue, which gives its colour to the skin; next follows the papillary tissue formed by the extremities of the nerves, and in which the sense of touch principally resides; the last and innermost layer is the skin proper, or leather, called Dermis, Derma, or Corium[1163]. Two of these layers M. Cuvier assigns to insects. They have, he observes, in every state, a true epidermis[1164]; and in their state of larva he finds that the infinite variety of colours that so adorn many of them is produced by a mucous substance observable between the epidermis and the muscles[1165]: this seems analogous to the rete mucosum. To this, dried and mixed with their horny substance, he attributes also the colours of the perfect insect: "for," says he, "when the Lepidoptera are in the chrysalis, the little coloured scales which are to ornament their wings, are then in a state of mucosity similar to that which is found under the skin of the caterpillar. The colours of the Arachnida," he goes on, "are also due to this mucosity: it is discoverable under the skin, and has the appearance of minute glandular points of which the shades vary considerably. But in the Coleoptera, and many other Orders, the colours of the skin are mixed in its horny tissue, nearly as those of the Testacea are in their calcareous shells"[1166]. In the perfect insects, therefore, in most cases, we may consider the epidermis and rete mucosum as together forming the exterior and coloured integument of insects--that part which in the table, since it is not properly an epidermis, I have distinguished by the name of Exoderma.

The learned author just quoted has observed nothing under the skin of white-blooded animals that he regards as analogous to nervous papillæ[1167]. In some parts of insects, as in the lamellæ of the antennæ of the Petalocera, and the extremities of the joints, especially the last, of many palpi, there is however an appearance of them; and it seems reasonable to suppose that where the sense of touch resides, there must, even in insects, be something of a papillary tissue.

With regard to the innermost integument of the vertebrate animals,--the leather, or real skin,--this learned comparative anatomist finds nothing analogous to it in the integuments of insects[1168]; but as he does not notice it, he appears to have overlooked the substance that lines the outer crust, or exoderma, in the Coleoptera and most other orders. This is not always easily detected; but it may generally be discovered by breaking, or rather tearing (not cutting), after having cleared away the muscles, any part of the body of an insect. It is always very visible on the under side of elytra[1169], but is not discoverable in tegmina. It appears to consist, in many cases, of several layers of a whitish membrane, and generally breaks into fibres. In some elytra of the larger Dynastidæ, towards the sides the exterior layer is separated from the rest by a kind of cellular substance. The fibrous structure of this inner skin (which I call the Esoderma) seems to give it some affinity to the skin of vertebrate animals[1170]. In many parts of the body, however, it appears to be merely a thin pellicle. A medical friend, to whom I showed specimens of it, thinks it a kind of cellular membrane.

2. A few words are next necessary with regard to the articulation of the integument, or the mode by which the several pieces of which it and its members consist, are united to each other. In some, as in several of the parts of the head, the occiput, vertex, temples, cheeks, &c.--the line of distinction is merely imaginary; in others an impressed line separates a part from its neighbours, as is the case with the nose in Vespa, &c. the head in the Arachnida. But in the majority of instances the parts are separated by a suture, or form a real joint. The kinds of articulation observed by anatomists in vertebrate animals do not all occur in insects, and they seem to have some peculiar to themselves. Thus, for instance, they have no proper suture; for though they exhibit the appearance both of the harmonic and squamose (ecailleuse Cuv.) sutures[1171], yet these parts being all limited by the esoderma, or skin, above noticed as lining the integument, and all admitting a degree of motion more or less intense, rather afford examples, as the case may be, of other kinds of articulation[1172]. Again, they have no proper Enarthrosis, or ball and socket; though the anterior coxæ of the Capricorn-beetles (Cerambyx L.) approach very near to this kind of articulation, as will be shown more fully in another place. The inosculating segments or rings, which distinguish the abdomen, and sometimes other parts of insects, are an example of a kind of articulation not to be met with in the Vertebrata. The ginglymous articulation, in which the prominences of the ends of two joints are mutually received by their cavities, and which admits only of flexion and extension, often prevails in the limbs, &c. of insects; but in many cases the joints are merely suspended to each other by a ligament or membrane; and, in fact, the integument of insects, with regard to its articulation, even where the joints ginglymate, may be said in general to consist of pieces connected by the internal ligament, membrane, or skin that lines it; for even in the legs, where the ginglymous articulation is sometimes very remarkable and complex, as will be shown to you hereafter, the joints are also connected by this substance, as you may see if you examine the legs of any Coleopterous insect.

The number of articulations or pieces that form the integument and its members in these animals, varies greatly in different tribes, genera, &c. Thus, in the common louse (Pediculus humanus) they scarcely reach fifty, while in some cockroaches (Blatta) they amount to more than eight times that number.

Having premised these observations on the external anatomy of the body in general, in the remainder of the present letter I shall confine myself to the consideration of the head and its parts.

I. The Head of insects, as the principal seat of the organs of sensation, must be regarded in them, as well as in the vertebrate animals, as the governing part of the body. It may be considered with respect to its substance, figure, composition, superficies, proportion, direction, articulation with the trunk, motions--and more particularly as to its parts and appendages.

i. With regard to its substance--the head may be said in general to be the hardest part of the crust: and it is so for very good reasons. In the first place, as it has to make way for the rest of the body when the animal moves, it is thereby best fitted to overcome such resistance as may be opposed by the medium through which it has to pass; in the next, as it bears the organs of manducation, it was requisite that it should be sufficiently firm and solid to support their action, which is often upon very hard substances; and besides this, as no motion of its parts inter se, as in the case of the trunk, is requisite to facilitate the play of its organs, a thin integument was not wanted.

ii. The most general law relative to the figure or shape of the head seems to be, that it should approach to that of an equilateral triangle, with its angles rounded, and the vertex being the mouth; and that the vertical diameter should be less than the horizontal, whether longitudinal or transverse. But the infractions of this law are numerous and various. Thus, in some insects an isosceles triangle is represented by the head, the length being greater than the breadth; in others, instead of being flat it is compressed, so that the horizontal diameter is less than the vertical; in others, again, it is orbicular, or round and depressed; in others nearly spherical: occasionally it is rather cylindrical. In many instances it is very long; in others the width exceeds the length. Though often narrowest before, in some cases the reverse takes place. Its anterior end is often attenuated into a long or short snout or rostrum, and its posterior into a long or short neck. Its contour, though usually regular, is sometimes either cut into lobes, or scooped out into sinuosities. But to enumerate minutely all the variations of form which take place in the head of insects would be endless; I shall therefore proceed to the next particular.

iii. The composition of the head is very simple; for, exclusive of its organs, it consists only of a single piece or box, without suture or segment, with an aperture at the end below to receive the instruments of manducation, others for the eyes and stemmata when present, and also for the antennæ. In the Arachnida, &c., in which the head is not separated from the thorax, it is merely a plate, the under-side or cavity of which is occupied and filled by the above instruments.

iv. With regard to its superficies, the head of insects is generally more or less uneven, though in some cases it presents no inequalities. In many of the Lamellicorn tribes, and a few other individuals, in one sex at least, as has been before observed[1173], it is armed with long horns, or prominent tubercles; it is often covered with numerous puncta, or pores; and some of its parts, as the nose, after-nose, &c. in particular groups, marked out by an impressed line[1174]. In many Hymenoptera, Diptera, &c. its upper surface is convex, and the lower concave; in others both surfaces are convex.

v. It is the most general rule, as to its proportion, that it shall be smaller than either trunk or abdomen; but in some instances, as in the S. American ant, Atta megacephala, it is much larger than either.

vi. By the direction of the head, I mean its inclination with respect to the prothorax. The most natural direction, or that which obtains most generally, is for it to form an angle more or less obtuse with the part just mentioned. This seems to obtain particularly in Coleoptera; but in some, as Mylabris, it is inflexed, forming an acute angle with it. In the Heteropterous Hemiptera (Cimex L. &c.) it is generally in the same line with the body, or horizontal; and in many Diptera it is vertical.

vii. We now come to a circumstance which will detain us longer, namely, its articulation with the trunk, or rather with its anterior segment, the prothorax.--M. Cuvier makes two principal kinds of articulation of the head upon the prothorax, in one of which the points of contact are solid, and the movement subordinate to the configuration of the parts; in the other, the articulation is ligamentous, the head and the thorax being united and kept together by membranes.

1. The first of these kinds of articulation--that by the contact of solid parts--takes place, he says, in four different ways. "In the most common conformation, in the part that corresponds to the neck, the head bears one or two smooth tubercles, which receive corresponding cavities of the anterior part of the prothorax observable in the Lamellicorn and Capricorn beetles. In this case the head can move backwards, and the mouth forwards and downwards. The second mode of solid articulation takes place when the posterior part of the head is rounded, and turns upon its axis in a corresponding cavity of the anterior part of the prothorax; as may be seen in Curculio, Reduvius, &c. The axis of motion is then at the centre of articulation, and the mouth of the insect moves equally backwards and forwards, upwards and downwards, to right and left.--The third sort of articulation, by solid surfaces, takes place when the head, truncated posteriorly, and presenting a flat surface, is articulated, sometimes upon a tubercle of the thorax, and sometimes upon another flat and corresponding surface, as in almost all the Hymenoptera and the majority of the Diptera. The disposition of the fourth kind of articulation allows the head only the movement of the angular hinge (le seul mouvement de charnière angulaire). The only examples at present known are in some species of Attelabus F. The head of these insects terminates behind in a round tubercle, received in a corresponding cavity of the thorax: the lower margin of this cavity has a notch, and permits the movement of the head only in one direction[1175]."

2. The second kind of articulation, the ligamentous, he affirms takes place only in orthopterous and some neuropterous insects: "The head in this kind of articulation is only impeded in its movements towards the back, because it is stopped there by the advance of the prothorax; but below it is quite free. The membranes or ligaments extend from the circuit of the occipital cavity to that of the anterior part of the prothorax, which gives a great extent to the movement[1176]."

When I consider the well-deserved celebrity of the great author whose words I have here quoted, and the great and useful light that the genius and learning which conducted his patient labours and researches have thrown over every department of comparative anatomy,--a science he may be almost said to have founded,--I feel the most intire reluctance to differ in any thing from an authority so justly venerable to all lovers of that interesting study. But, however great my diffidence and hesitation to express an opinion at all opposed to his, the interests of truth and science require that I should state those particulars in which my own observations, made upon a careful examination of various insects of every Order, have led to results in some respects different from the above. "Aliquando bonus dormitat Homerus;" and if the Genius of Comparative Anatomy ever nodded, it sometimes happened when he was examining the structure of insects. An instance of this with regard to the mouth of the bee has been noticed by Mr. Savigny[1177]; and indeed it is not wonderful that in so extensive an undertaking, in which the number of examples to be examined upon every branch of his subject must be immense, that he did not always scrutinize minutely those that seemed less important. Every writer on every department of Natural History, especially where the objects of research, as in the insect world, are so infinite in number, will be liable to such mistakes; but these will meet with due allowance from every candid mind--

"Hanc veniam damus, petimusque vicissim:"

and I shall express my trust that you will overlook any errors of mine; and doubtless I shall not be free from them--

"---------Quas aut incuria fudit, Aut humana parum cavit natura----"

The two kinds of articulation of the head which our learned author has stated as the principal ones, will, I think, be found upon examination not so widely distant as his expressions seem to indicate; for in fact in all insects, as well as the Orthoptera, this part is suspended by a membrane or ligament which unites the margins of the occipital cavity with those of the anterior one of the prothorax: thus forming all round some protection to the organs that are transmitted from the head through the latter part to the rest of the body. Though the head in most Orthoptera is not partly received into the cavity of the prothorax, as is the case in the Order Coleoptera, but is rather suspended to it, yet in some instances, for example in the mole-cricket (Gryllotalpa vulgaris), it is partially inserted.

Again: when, in his first mode of articulation by contact of solid parts, he speaks of one or two smooth tubercles of the neck, with their corresponding cavities in the prothorax, as forming the most common conformation, you would expect to find examples of this in very many insects; yet upon a close examination, unless in Oryctes nasicornis[1178], and perhaps in others of the Dynastidæ MacLeay, you would scarcely meet with any thing that could be called a tubercle and its corresponding cavity in the neck or prothorax of any Lamellicorn or Capricorn beetle that you might chance to examine. You would find, indeed, that the occiput was usually smooth and very slippery, as if lubricated; that in its margin were one or two notches (Myoglyphides), with muscles attached to them; that in the former of these tribes, the Lamellicorns, it projected on each side so as to form a more or less prominent angle; and that the throat (jugulum) was very convex, and lodged in a cavity of the lower margin of the prothorax: but further appearances of tubercles &c. you would in vain look for even in this tribe; and in the Capricorns you would find that the general conformation in this respect belonged to our learned author's second mode of solid articulation, resembling that of the majority of the weevils (Curculio L.), in which the head has no projecting angles or tubercles, or other elevation, but is received usually into the circular cavity of the prothorax.

His third mode of this articulation, that of the Hymenoptera and Diptera, is so peculiar, that it ought to be considered as a primary kind; since in this the head moves upon the prothorax as upon a pivot, and has a kind of versatile motion.

With regard to his fourth mode, which from his description appears to be that of Apoderus Oliv., he allows motion to the head only in one direction, observing that the lower margin of the prothoracic cavity has a notch. But M. Latreille calls the articulation of the head in this genus an Enarthrosis[1179], which admits motion in every direction; and if you examine the common species (A. Coryli), you will find that the prothorax has a sinus taken out of its upper margin, as well as out of its lower one--which at any rate will allow a motion upwards.

I merely mention these little inaccuracies, with due diffidence, as some apology for giving you a different and at least a more popular and general view of this part of my subject, which I shall now proceed to state to you. It seems to me most convenient for the Entomologist, and most consonant to nature, to divide insects, with respect to the articulation of the head with the trunk, into three primary sections, each admitting one or more subdivisions.

1. The first consists of those whose head inosculates more or less in the anterior cavity of the chest; and whose articulation, therefore, seems to partake in a greater or less degree of the ball and socket (Enarthrosis). The head, however, is often capable of being protruded from this cavity. If you take into your hand any common Harpalus that you may find under a stone, you will see, if pressed, that it can shoot forth its head, so as to be entirely disengaged from the prothorax: a neck of ligament intervening between them[1180]: of course this power of protruding the head enables the animal to disengage it at its will from the restriction imposed upon its motions by the surrounding margin of the prothoracic cavity. To this section belong all the Coleoptera, the Heteropterous Hemiptera (Cimex L., &c.), and some of the Neuroptera (Raphidia, Semblis, &c.).--It may be further divided into two subsections--those, namely, whose head inosculates in the prothorax by means of a neck: as for instance Latreille's Trachelides, Apoderus, and the Staphylinidæ, amongst the beetles; the Reduviadæ amongst the Heteropterous insects, and Raphidia in the Neuroptera; and those whose head inosculates in the prothorax without the intervention of a neck; as, the Petalocera, the aquatic beetles (Dytiscus, Hydrophilus, &c.), and most of the genus Curculio L. in the first of these orders, the great body of the Cimicidæ in the second, and Semblis, Corydalis, &c. in the third.

2. The second section consists of those insects whose head does not inosculate in the chest, but is merely suspended to it by ligament or membrane. To this belong most of the tribes of the Orthoptera Order, with the exception of the Mantidæ, the Dermaptera, the Homopterous Hemiptera, and such of the Aptera as have the head distinct from the prothorax.--This section admits of a triple subdivision: those, namely, whose head is wholly covered by the shield of the prothorax, as in Blatta L.; those whose head is partly covered by it, as Gryllotalpa, and other Gryllina; and those whose head is quite free, not being at all impeded in its motion by the prothorax, as the Dermaptera, Nirmus, Pediculus, &c.

3. The third section consists of those whose head is truncated posteriorly, and flat or concave, with a very small occipital aperture, and is attached to a neck of the prothorax upon which it turns, or is merely suspended to that part. This includes the Lepidoptera, Hymenoptera, Diptera, the Libellulina, &c. in the Neuroptera, and the Mantidæ in the Orthoptera. Three subsections at least, if not more, present themselves in this section: the first is, of those whose head is united to the prothorax, without the latter forming any neck. To this belong the Lepidoptera, Trichoptera? The second is of those the upper side of whose thoracic neck is ligamentous; and here you may range most of the Hymenoptera. The third is of those in whom it is a continuation of the ordinary integument. In this subsection the Diptera, Libellulina and Mantidæ will find their place. In this last section the head appears to turn upon the thorax as upon a pivot.

Before I finish what I have to say on the articulation of the head, I must direct your attention to the analogies that hold in this respect between the different tribes. Thus the Coleoptera are analogous to the Heteropterous Hemiptera; the Orthoptera, with the exception of the Mantidæ, to the Homopterous Hemiptera; the Mantidæ to the Libellulina; the Lepidoptera to the Trichoptera; the Hymenoptera to the Diptera, with a slight variation, and probably others might be traced.

viii. A word or two upon the motions of which the head of insects is capable. M. Cuvier, in the extracts lately laid before you, speaks of different powers of movement as the result of different configurations of the parts of the head. This probably is correct with regard to many cases; but a great deal will depend upon the power the insect has of protruding its head and disengaging its base from the restriction of the prothorax; for where, like the Harpali, Staphylini, &c. it is able to do this, it can probably move its head in every direction. It is only where the ligaments are less elastic, or allow of little tension, that its movements are confined; and few living insects have been sufficiently examined to ascertain how far this takes place. In those cases belonging to the third section of articulations, in which the head moves upon the thorax as upon a pivot, as is the case with Hymenoptera and Diptera, the movement is nearly versatile. I have seen a fly turn its head completely round, so that the mouth became supine and the vertex prone; and from the form and fixing of the head, it should seem that those of the Mantidæ were endued with the same faculty.

ix. The parts and appendages of the head are now in the last place to be considered. I shall begin with the Mouth, or rather the orifice in which the trophi or organs of manducation are inserted. In some insects, as was before observed, they occupy all the under-side of the head, as in the Arachnida, Myriapoda, &c; but in the great majority they fill an orifice in its anterior part, which in some instances, as in Lampyris, the Lepidoptera, Cimex L., Truxalis, appears to be nearly under the head; but in general it terminates that part, though it extends further below than above. In Chermes, a Homopterous genus, the promuscis is stated to be in the Antepectus, and consequently the mouth; but, as I shall endeavour to prove to you hereafter, this is a fallacy. In the males of the species of Coccus there is no mouth at all. In that of the elm (C. Ulmi) in lieu there are ten little shining points, arranged two before and two behind in a line, and three on each side in a triangle[1181]. It is to be observed that the orifice of which I am speaking is usually much smaller in those insects which take their food by suction, the Hemiptera, Lepidoptera, Diptera, &c., than in the masticating tribes. With regard to the real mouth, or that through which the food enters, I have nothing at present to observe, except that it lies between the upper-lip and tongue, is sometimes covered by a valve, as in Apis, Vespa[1182], &c., and is different in the masticators and suckers.

* * * * *

I shall next offer a few observations seriatim, as they stand in the Table, upon the organs of manducation; which, to avoid circumlocution, instead of Instrumenta cibaria, the name Fabricius gave them, I shall call trophi or feeders. It is upon these parts, you are aware, that the system of the celebrated Entomologist just mentioned is founded; and could they always, or even for the most part, be inspected with ease, they would no doubt afford characters as various and discriminative as those of the vertebrate animals. Differences in these parts indicate a difference in the mode in which the animal takes its food, and often in the kind of food, and sometimes in its general economy and habits,--circumstances which are powerful and weighty in supporting the claim of any set of animals to be considered as forming a natural genus or group. Trifling variations, however, of these parts, unless supported by other characters and qualities, ought not to have much stress laid upon them, since, if we insist upon these, in some tribes almost every species might be made a genus.

With respect to their trophi in general, insects of late have been divided into two great tribes[1183], masticators and suckers; the first including those that are furnished with instruments to separate and masticate their food; namely, an upper- and under-lip (labrum and labium), upper- and under-jaws (mandibulæ and maxillæ), labial and maxillary palpi, and a tongue (lingua): and the second those in which these parts are replaced by an articulate or exarticulate machine, consisting of several parts and pieces analogous to the above, which pierce the food of the animal, and form a tube by which it sucks its juices. If, however, the mode in which insects take their food be strictly considered, it will be found that in this view they ought rather to be regarded as forming three tribes; for the great majority of the Hymenoptera order, and perhaps some others, though furnished with mandibles and maxillæ, never use them for mastication, but really lap their food with their tongue: these, therefore, might be denominated lappers.

When a mouth is furnished with the seven ordinary organs used in taking the food and preparing it for deglutition--I mean the upper-lip and the two upper-jaws; the under-lip and the two under-jaws, including the labial and maxillary palpi; and the tongue--I denominate it a perfect mouth; but when it is deficient in any of these organs, or they exist merely as rudiments, or when their place is supplied by others, (which, though they may be analogous parts, have little or no connection with them in their use or structure,) I denominate it an imperfect mouth. This last I would further distinguish, according to the nature of its trophi, by other and more distinctive terms, as I shall presently explain to you.

1. Labrum[1184].--I shall first consider the organs present in a perfect mouth, beginning with the upper-lip (labrum). This part, which Fabricius sometimes confounded with the nose, miscalling it clypeus, is usually a moveable[1185] piece, attached by its base to the anterior margin of the part last named, and covering the mouth, and sometimes the mandibles, from above. In insects in their last state it is usually of a horny or shelly substance; yet in some cases, as in Copris and Cetonia, beetles that imbibe juices, it is membranous. In form and shape it varies greatly, being sometimes nearly square, at others almost round; in some insects representing a parallelogram, in others a triangle, and in many it is oblong. In some instances it is long and narrow, but more generally short and wide. It is often large, but occasionally very minute. In the majority it has an intire margin, but it is not seldom emarginate or bilobed, or even dentate. Its surface is commonly even, but it is sometimes uneven, sometimes flat, at others convex, and in a few species armed with a short horn or tubercle[1186]. As to its pubescence, it is often naked, but now and then fringed or clothed with down or hairs, or sprinkled with bristles. It consists in almost every instance of a single piece; but an exception to this occurs in Halictus, a little bee, in the females of which it is furnished with a slender appendage[1187].--The direction of the upper-lip is various. It is rarely horizontal, or in the same line with the nose, often vertical; it sometimes forms an obtuse angle with the anterior part of the head, and occasionally an acute one, when it is more or less inflexed. The use of this part is ordinarily to close the mouth from above, to assist in retaining the food while undergoing the process of mastication; but in many Hymenopterous insects its principal use seems to be, to keep the trophi properly folded; and in some cases where it is inflexed, as in the leaf-cutter bees (Megachile Latr.), to defend its base, while the mandibles are employed, from injury by their action[1188].

2. Labium[1189].--On the under-side of the head, and opposed to the upper-lip, the mouth is closed by another moveable organ, concerning the nomenclature and analogies of which Entomologists have differed considerably. At the first view of it, this organ seems a very complex machine, since the under-jaws or maxillæ are attached to it on each side, and the tongue is often seen to emerge from it above, so as to appear merely a part of it; but as the former answer to the upper-jaws, and the latter is the analogue of the part bearing the same name in the vertebrate animals, I shall consider these as distinct and primary organs, and treat of the under-lip (labium) of which I am now speaking, by itself. Linné takes no notice of this part, but his illustrious compatriot and cotemporary, De Geer, did not so overlook it: he appears to consider the whole apparatus, including the maxillæ, as the labium[1190]; but sometimes he distinguishes the middle piece by that name[1191]; and the tongue, in the case of the stag-beetle, he denominates a proboscis (trompe)[1192]. In the Hymenoptera he calls this part tongue, under-lip, and proboscis: but seems to prefer the last term[1193]. Fabricius originally regarded the whole middle piece as a labium[1194]; but afterwards (though his definition is not accurate, since he assigns the palpi to the ligula, which he affirms is covered by the labium--circumstances by no means universal in Coleoptera) he considers this as consisting of ligula and labium[1195]. Latreille at first regarded the ligula of Fabricius as the labium, and called the labium of that author the mentum[1196]; but afterwards he gave the name of labium to the whole middle piece of the lower apparatus of the mouth--calling the upper piece, with Fabricius, the ligula, and retaining the denomination of mentum for the lower[1197].

If the circumstances of the case are duly considered, I think you will be convinced that the term under-lip, or labium, should be confined to that part which the learned Dane so named. For I would ask, Which is the part on the under side of the head that is the antagonist, if I may so speak, of the upper-lip or labrum? Is it not that organ which, when the mouth is closed, meets that part, and in conjunction with it shuts all in? Now in numerous insects, particularly the Lamellicorn beetles (Scarabæus and Lucanus L.), this is precisely the case. In the Predaceous beetles, indeed, (Cicindela, Carabus, Dytiscus L. &c.) the under-lip does not meet the upper, to close the mouth and shut in the tongue; neither can the tongue be said so to do, but only, from some circumstances connected with its manner of taking its food, it is requisite that the last-mentioned organ should not be retractile or covered; but its miscalled mentum is still the analogue of that part which helps to close the mouth in the former tribe. Should not this, therefore, which so often performs the office, be distinguished by the name, of a lip? Again, is it not rather incongruous to consider that organ which confessedly more or less performs the office of a tongue, as a part of the lip? Though it often wears that appearance, yet I believe, if the matter is thoroughly and patiently investigated, it will be found that on their upper side its roots are attached to the interior of the upper side of the head, as well as on their lower side to the labium; so that it may be regarded as common to the two lips, and therefore not properly considered as an appendage of the under-lip alone.

Having assigned my reasons for preferring the name given to the part in question by Fabricius, rather than that of Latreille, I shall next make my observations on the part itself. In many cases the labium, or the middle piece of the lower oral apparatus, appears to consist of two joints: this you may see in the great water-beetle (Hydrophilus piceus), the burying-beetles (Necrophorus), the Orthopterous tribes[1198], the Hymenoptera[1199], and others. In this case the upper or terminal piece is to be regarded as the labium, and the lower or basal one (which Mr. MacLeay calls the stipes) as the mentum or chin--at other times, as in some Lamellicorn beetles, the only separation is a transverse elevated line, or an obtuse angle formed by the meeting of the two parts, and very frequently there is no separation at all, in which case the whole piece, the mentum merging in it, may be denominated the labium.

With respect to its substance, the labium in most Coleopterous insects is hard and horny, in Necrophorus it is membranous, and the mentum harder; in Prionus coriarius, our largest Capricorn-beetle, both are membranous; in the bee-tribes, Apis L., the labium rather resembles leather, while the mentum is hard. Its surface is often convex, sometimes plane, and sometimes even concave; as for instance in Melolontha Fullo, a rare chafer occasionally found on the coast of Kent. In some it is covered with excavated points; in others it is quite smooth. In numbers, as in the Predaceous beetles, both labium and mentum are perfectly naked; in others, as in the common cockchafer, they are hairy; in Geniates barbatus Kirby, another chafer in the male insect, the labium is naked, while the mentum, which forms a piece distinct from that part, is covered with a dense rigid beard[1200]. In shape the whole labium varies considerably, much more than the labrum; for in addition to most of the forms I enumerated when I described that organ, which I shall not here repeat, you may meet with examples of many others. Thus, to instance in the Petalocerous tribes (Scarabæus L.), in some, as in the Rutelidæ, the labium is urceolate, or representing in some degree the shape of a pitcher[1201]; in others it is deeply concave, and not a little resembles a basin or a bowl[1202]; this form is peculiar to the labium of Cremastocheilus Knoch, a scarce North American beetle; in another related to this, but of an African type (Genuchus Kirby MS. Cetonia cruenta F.), it is a trapezoid plate, which is elevated from the head, and hangs over the throat like a chin[1203]. In the Hymenoptera it is extremely narrow and long, and embraces the sides of the tongue, as well as covering it from below; so that it wears the appearance of a kind of tube[1204]. Generally speaking, the length of the labium exceeds its breadth; but in the Predaceous beetles the reverse of this takes place, it being very short and wide, and usually terminating towards the tongue in three lobes or teeth which form two sinuses varying in depth[1205].

The mentum taken by itself affords no very striking characters to which I need call your attention: I shall only observe, that in Hymenoptera it is generally of a triangular shape[1206]; but before I proceed to consider the labial palpi, it will be proper to notice the remarkable labium of Orthopterous insects, and of the Libellulina, between which there is no little analogy. At first you would imagine the terminal part of this organ in the former to be the analogue of the tongue, or ligula F.; as it is indeed generally regarded by modern Entomologists[1207]. It seems, like the tongue of the Carabi L., Dytisci, &c., to be a distinct piece, which has below it both labium and mentum; but when you look within the mouth, you will find a linguiform organ[1208], which evidently acts the part of a tongue, and therefore ought to have the name; and the piece just alluded to must either be regarded as the termination of the lip, or as an external accompaniment of the tongue, analogous, it may be, to the paraglossæ in bees[1209]. In a specimen of Acrida viridissima (Locusta F.) which I dissected, the tongue is as long as the appendage of the under-lip, and by its upper surface seems to apply closely to it. In the Libellulina a similar organ is discoverable[1210], which on its upper-side terminates in the pharynx, like that of one of the Harpalidæ before mentioned. In the Orthoptera, therefore, I regard the labium as consisting of three articulations, the upper one divided into two, three, or more lobes[1211]; the intermediate one more directly answering to the labium of other insects, and the basal one or mentum. This organ in the Libellulina is of a different structure: it has only two articulations representing labium and mentum; but the former consists of three parallel pieces, the two exterior ones rising higher than the intermediate one, and at their inner angle having an acute sinus from which the palpi emerge; and the intermediate piece, which is longitudinally channelled, lapping over the inner side of the lateral pieces. From the angle of the covered part of these pieces, a subulate short horizontal horn points inwards towards the tongue, which it must keep from closing with the labium[1212].

3. Palpi Labiales[1213].--The last-mentioned organs, the labial palpi, next claim our attention; but before I advert particularly to them, it will be proper to premise a few words upon palpi, or feelers, in general. These are usually jointed moveable organs, of a corneous or coriaceous substance, attached by ligaments to the labium and maxillæ, and in the Crustacea even to the mandibulæ. Their joints, which are usually more or less obconical, articulate also in each other by ligaments, with perhaps some little mixture of the ball and socket. Their ends, the last joint especially, seem furnished with nervous papillæ which indicate some peculiar sense, of which they are the instrument. What that sense is has not been clearly ascertained, and concerning which I shall enter more into detail in another place. Their motion seems restrained, at least in some, to two directions, towards and from the mouth. They were called palpi or feelers, because the insect has been supposed to use them in exploring substances. There seem to be no organs in the vertebrate animals directly analogous to the palpi of insects and Crustacea, unless, perhaps, the cirri that emerge from the lips of some fishes, as the cod, red mullet, &c. which Linné defines as used in exploring (prætentantes). Whether the vibrissæ, miscalled smellers, of some quadrupeds and birds have any reference to them, I will not venture to affirm; but the feline tribe evidently use their bristles as explorers, and they are planted chiefly in the vicinity of the mouth.

Having made these general remarks, I shall now confine myself to the labial palpi. I call them labial palpi, because that term is in general use, and because in many cases they really do emerge from what I consider as the labium, as in most of the chafers; but they might with equal propriety be denominated lingual palpi, since they sometimes appear to emerge from the tongue as in the stag-beetle (Lucanus Cervus). In some instances, as in the Predaceous beetles, they seem to be common to both labium and tongue, being attached at their base on the upper side to the former, and on the under side to the latter. As to their situation: they emerge from the base of the labium in the locusts (Locusta Leach)[1214]; from its middle in Hister maximus[1215]; from its summit in Amblyterus MacLeay[1216]; and from its lateral margin in Dynastes MacLeay, &c. They consist of from one to four joints; which, I believe, they never exceed. They vary in length; though generally shorter than the maxillary palpi, yet in the ferocious tiger-beetles (Cicindela L.) they equal them in length; and in the hive-bee and humble-bees, and many other bees, they are considerably longer[1217]. The two first joints of these palpi, however, in these bees are different in their structure from the two last, being compressed and flat, or concave; and the two last joints, instead of articulating with the apex of the second, emerge from it below the apex: so that these two first joints seem rather elevators of the palpi than really parts of them[1218]. With respect to the relative proportions of their joints to each other: in some cases the first joint is the longest and thickest, the rest growing gradually shorter and smaller[1219]; in others, the second is the longest[1220]; in others, again, the third[1221], and sometimes the last[1222]; and often all are nearly of the same size and length[1223]. They are more commonly naked, but sometimes either generally or partially hairy. Thus in Cicindela, the last joint but one is usually planted with long snow-white bristles in a double series, while the rest of the joints have none; and in Copris Latr. all of them are extremely hairy. In shape they do not vary so much as the maxillary palpi, being most frequently filiform or subclavate, and sometimes setaceous; the last joint varies more in shape than the rest, and is often remarkably large, triangular, and shaped like the head of a hatchet[1224]; and at others it resembles the moon in her first quarter[1225]. In the great dragon-fly, or demoiselle if you prefer the gentler French name (Æshna F.) the labial palpi, which are without any visible joints, are terminated by a minute mucro or point[1226]. With regard to their direction and flexure, they frequently, as in the instance just mentioned, turn towards each other, and lie horizontally upon the end of the labium. Sometimes, as in the Cicindelidæ, they appear to point towards the tail of the insect, the last joint rising, and forming an angle with the rest of the feeler. In other instances they diverge laterally from the labium, the last joint turning again towards it at a very obtuse angle.

4. Mandibulæ[1227].--Having considered the analogues of the lips in our little beings, I must next call your attention to the representatives of the jaws. The vertebrate animals, you know, are mostly furnished with a single pair of jaws, one above and the other below, in which the teeth are planted and which have a vertical motion. But insects are furnished with two pair of jaws, a pair of upper-jaws and a pair of under-jaws, which have no teeth planted in them, and the motion of which is horizontal.--I shall begin with an account of the upper-jaws. These by modern Entomologists, after Fabricius, are denominated mandibles (mandibulæ): a term appropriated by Linné to the beaks of birds. The upper-jaws of insects this great naturalist named maxillæ--and not improperly, since the office of mastication is more peculiarly their office than that of the under-jaws, which Fabricius has distinguished by that name: as the term mandible, however, is generally adopted, I shall not attempt to disturb it.

The mandibles close the mouth on each side under the labrum or upper-lip. They are generally powerful organs, of a hard substance like horn; but in the Lamellicorn beetles of Mr. MacLeay's families of Scarabæidæ and Cetoniadæ, they are soft, membranous, and unapt for mastication. In Coleopterous insects they commonly articulate with the head by means of certain apophyses or processes, of which in many cases there are three discoverable at the exterior base of the mandibles; one, namely, at each angle, and one in the middle. That on the lower side is usually the most prominent, and wears the appearance of the condyle of a bone: it is received by a corresponding deep socket (or cotyloid cavity) of the cheek, in which, being perfectly smooth and lubricous, it moves readily, but without synovia, like a rotula in its acetabulum. The upper one projects from the jaw, forms the segment of a circle, and is concave also on its inner face. A corresponding more shallow, or, as anatomists speak, glenoid cavity of the cheek, where it meets the upper-lip, receives it, and the concave part admits a lubricous ball projecting from the cheek, upon which it turns[1228]. This structure you will find in the stag-beetle, and some other timber-devourers. Other Coleoptera have only a process of a similar structure at each of the dorsal angles of the base of the mandible, the intermediate one being wanting; and the articulation does not materially differ, as far as I have examined them, in the Hymenoptera and Neuroptera. In the Orthoptera, the structure approaches more nearly to that of the stag-beetle, since there are three prominences: it is thus well described by M. Marcel de Serres: "This articulation," says he, "takes place in two ways. At first, in the upper surface of the mandible, and at its base, may be observed two small prominences and a glenoid cavity; these prominences are received in two glenoid cavities excavated in the shell of the front, as the cavity of the mandible receives a small prominence of the same part. Below the mandible, and at its base, there is a kind of condyle, which has its play in a cotyloid cavity excavated in the shell of the temple, far below the eye, and at the extremity of the coriaceous integument of the head[1229]." Within the head in this order, at least in Locusta Leach, is a vertical septum, which divides the head into two chambers, as it were, an occipital and a frontal, consisting of a concave triangular stem, terminating in two narrower concave triangular branches, so as to resemble the letter Y, and forming three openings, an upper triangular one, and two lateral subquadrangular ones, which last are the cavities that receive the base of the mandibles. This partition, which I would name Cephalophragma, doubtless affords a point of attachment to many of the muscles of the head. It does not appear to have been noticed, unless it be synonymous with the intermaxillary arcade of Marcel de Serres[1230]. Probably a corresponding support to the muscles, &c. may exist, as we have seen it does in Vespa L.[1231], in many other heads of the different Orders, which have not yet fallen under examination. Many mandibles, as those of the hornet &c., appear to be suspended to the cavity of the head on the inside by a marginal ligament sufficiently relaxed to admit of their play: those of the Orthoptera, M. Marcel de Serres informs us, are united to the head by means of two cartilages, the outermost being much the shortest, to which their moving muscles are attached. These he considers as prolongations of the substance of the mandible[1232]. The bottom of mandibles, when cleared of the muscles &c., inclines almost universally to a triangular form; but in some cases, as in the stag-beetle, it is nearly a trapezium. I cannot conclude this subject without noticing the motions of the mandibles. What the author lately quoted has said with regard to those of the Orthoptera, will, I believe, apply equally well to all the mandibulate orders. "The articulation of mandibles with the skull appears to take place by two points solely; and as these parts only execute movements limited to a certain direction, they may be referred to ginglymus[1233].--The movements of mandibles are limited to those from within outwards, and from without inwards[1234]." Whether they are restricted from any degree of vertical motion, has not yet been proved, as the jaws of vertebrate animals move horizontally as well as vertically--so those of insects may have some motion vertically as well as horizontally; and it seems necessary for some of their operations that they should. I am not anatomist enough to speak with confidence on the subject, but the ball and socket articulation at the lower part of the mandible, and the curving one at the upper, though a kind of ginglymus, seems to imply a degree of rotatory movement, however slight.

I must next say something upon the general shape of these organs. Almost universally they incline to a triquetrous or three-sided figure, with their external surface convex, sometimes partially so, and their internal concave. Most frequently they are arched, curving inwards; but sometimes, as in Prionus octangularis[1235], a Capricorn beetle, and others of that genus, they are nearly straight; and in Rhina barbirostris[1236], a most remarkable Brazilian weevil, their curvature is outwards. In Pholidotus lepidotus MacLeay, and Lucanus Elephas, two insects of the stag-beetle tribe, they are bent downwards; and in Lucanus nebulosus K. (Ryssonotus MacLeay) they turn upwards[1237]. They are usually widest at the base, and grow gradually more slender to the apex, but in the hornet (Vespa Crabro) the reverse takes place, and they increase in width from the base to the apex; and in the hive-bee, and others of that tribe, they are dilated both at base and apex, being narrowest in the middle; others are nearly of the same width every where. In those insects that use their mandibles principally for purposes connected with their economy, they are often more broad in proportion to their thickness, than they are in those which use them principally for mastication. In the locust tribes (Locusta Leach), they are extremely thick and powerful organs, and fitted for their work of devastation; but in the glow-worm (Lampyris), they are very slender and minute. In those brilliant beetles, the Buprestes, they are very short; but in the stag-beetles, and those giants in the Capricorn tribe, the Prioni, they are often very long[1238]. They either meet at the summit, lap over each other, cross each other, or are protended straight from the head; as you have doubtless observed in the stag-beetle, whose terrific horns are mandibles of this description. These organs are usually symmetrical, but in some instances they are not: thus in Hister lævus, a kind of dung-beetle, the left hand mandible is longer than the right; in Creophilus maxillosus K. (Staphylinus L.), a common rove-beetle, in the left hand mandible the tooth in the middle is bifid, and in the right hand one intire; and in Bolbocerus K. the mandible of one side, in some species the dexter, and in others the sinister, has two teeth, and the other none.

The next circumstance with respect to these organs which demands our attention, is the teeth with which they are armed. These are merely processes of the substance of the mandible, and not planted in it by gomphosis[1239], as anatomists speak, as they are in vertebrate animals. They have, however, in their interior, at the base at least, in the Orthoptera, a coriaceous lamina that separates them in some sort from the body of the mandible[1240]. Many insects, however, have mandibles without teeth; some merely tapering to a sharp point, others obtuse at the end, and others truncated[1241]. Of those that have teeth, some have them on the inside at the base, as Manticora, an African tiger-beetle[1242]; others in the middle, as Staphylinus olens, a rove-beetle, Lethrus cephalotes, &c.[1243]; others at the end, as many weevils (Curculio L.)[1244]; others again on the back, as the Rutelidæ, a tribe of chafers[1245], and Lethrus, a beetle just named; others once more on the lower side of the base, in the form of a tooth or spine, as in Melitta spinigera, a species of wild-bee, and some of its affinities[1246]; and lastly, others on the upper side of the base in the form of a long tortuous horn, as in that singular wasp Synagris cornuta F. before noticed as a sexual character[1247]. In the stag-beetle tribes (Lucanus L.) these teeth are often elongated into short lateral branches, or a terminal fork[1248]. They are sometimes truncated, sometimes obtuse, and sometimes acute.

But with regard to their kind, it will be best to adopt the ideas of M. Marcel de Serres; for though his remarks are confined to the Orthoptera, they may be applied with advantage to the teeth that arm the mandibles of insects in general. He perceives an analogy between those of this Order and the teeth of quadrupeds; and therefore divides them into incisive or cutting, laniary or canine, and molary or grinding teeth. He denominates those incisives that are broad, having in some degree the shape of a wedge, their external surface being convex, and their internal concave; whence they are evidently formed for cutting. The laniaries are those which have a conical shape, are often very acute, and in general the longest of any; and in some insects, as the carnivorous Orthoptera (and the Libellulina), they cross each other. The molaries are the largest of all, and their purpose is evidently to grind the food. There is never only a single one to each mandible, while the number of the incisives and laniaries is very variable. As the molaries act the principal part in mastication, they are nearer the inner base of the mandible or point of support: they serve to grind the food, which has been first divided by the incisives or torn by the laniaries. The carnivorous tribes are destitute of them; in the omnivorous ones they are very small, and in the herbivorous ones they are very large[1249]. So that in some measure you may conjecture the food of the animal from the teeth that arm its mandibles. Of incisive teeth you may find an example in those that arm the end of the mandibles of most grasshoppers (Locusta), and of the leaf-cutter-bees (Megachile Latr.)[1250]; of the laniary or canine teeth, you will find good examples in the mandibles of the dragon-flies (Libellulina); the two external teeth of the apex of those of the leaf-cutter bees may be regarded as between the incisives and laniaries; and the pointed mandibles without teeth may be deemed as terminating in a laniary one[1251]. The lower part of the inner or concave surface of the mandibles of grasshoppers will supply you with instances of the molary teeth, and the apex, also, of those of some weevils, as Curculio Hancocki K.[1252] But the most remarkable example of a molary organ is exhibited by many of the Lamellicorn beetles, especially those that feed upon vegetables, whether flower or leaf.--Knoch, who indeed was the first who proposed calling mandibles according to their teeth, incisive, laniary, or molary, but who does not explain his system clearly, observed that the mandibles of some Melolonthæ have a projection with transverse, deep furrows, resembling a file, for the purpose of bruising the leaves they feed upon[1253]: and M. Cuvier, long after, observed that the larvæ of the stag-beetle have towards their base a flat, striated, molary surface; though he does not appear to have noticed it in any perfect insect[1254]. This structure, with the exception of the Scarabæidæ and Cetoniadæ, seems to extend very generally through the above tribe; since it may be traced even in Geotrupes, the common dung-chafer, in which at the base of one mandible is a concave molary surface, and in the other a convex one, but without any furrows: a circumstance that often distinguishes those that have furrows.--In the Dynastidæ the affinity of structure with the Melolonthidæ &c. is more pronounced, the furrows to which ridges in the other mandible correspond being reduced to one or two wide and deep ones; whereas in some of the latter tribe they are very numerous. These mandibles, in many cases, at their apex are furnished with incisive teeth to cut off their food, and with miniature mill-stones to grind it[1255]. The part here alluded to I call the Mola.

Were I to ask you what your idea is with regard to the use of the organs we are considering, you would perhaps reply without hesitation, "Of what possible use can the jaws of insects be but to masticate their food?" But in this you would in many instances be much mistaken; as you will own directly if you only look at the mandibles of the stag-beetle--these protended and formidable weapons, as well as those of several other beetles, cannot be thus employed. "Of what other use, then, can they be?" you will say. In the particular instance here named, their use, independent of mastication, has not been satisfactorily ascertained; but in many other cases it has. Recollect, for instance, what I told you in a former letter, of those larvæ that use their unguiform mandibles as instruments of motion[1256]. Again: amongst the Hymenopterous tribes, whose industry and varied economy have so often amused and interested you, many have no other tools to aid them in their various labours and mechanical arts: to some they supply the place of trowels, spades, and pick-axes; to others that of saws, scissors, and knives--with many other uses that might be named. In fact, with the insects of this intire Order mastication seems merely a secondary, if it is at any time their use. Still comprehending in one view all the mandibulate Orders, though some use their mandibles especially for purposes connected with their economy, yet their most general and primary use is the division, laceration, and mastication of their food; and this more exclusively than can be affirmed of the under-jaws (maxillæ). This will appear evident to you, when you consider that insects in their larva state, in which universally their primary business is feeding, with very few exceptions use the organs in question for the purpose of mastication, even in tribes, as the Lepidoptera, that have only rudiments of them in their perfect state--while the maxillæ ordinarily are altogether unapt for such use. The exceptions I have just alluded to are chiefly confined to the instance of suctorious mandibles; or those which, being furnished at the end with an orifice, the animal inserting them into its prey, imbibes their juices through it. This is the case with the larvæ of some Dytisci, Hemerobius, and Myrmeleon[1257]; and spiders have a similar opening in the claw of their mandibles, which is supposed to instil venom into their prey[1258].

Under this head I must not pass without notice an appendage of the mandibles, to be found in some of the rove-beetles (Staphylinidæ), as in Ocypus, Staphylinus, and Creophilus Kirby. In the first of these it is a curved, narrow, white, subdiaphanous, submembranous, or rather cartilaginous piece, proceeding from the upper side of the base of the mandible[1259]; in the second it is broader, straighter, and fringed internally and at the end with hairs; and in this at first it wears the appearance of being attached laterally to the mandible under the tooth[1260], but if closely examined, you will find that it is separate: in Creophilus maxillosus it is broader. This is the part I have named prostheca. It is perhaps useful in preventing the food from working out upwards during mastication.

5. Maxillæ[1261]. The antagonist organs to the mandible in the lower side of the head, are the under-jaws, or maxillæ--so denominated by the illustrious Entomologist of Kiel. Linné appears to have overlooked them, except in the case of his genus Apis, in which he regards them, and properly, as the sheath of the tongue. De Geer looked upon them in general as part of the apparatus of the under-lip or labium; and such in fact they are, as will appear when we consider them more particularly. Fabricius has founded his system for the most part upon these organs, the principal diagnostic of ten out of his thirteen Classes (properly Orders) being taken from them; and in the modern, which may be termed the eclectic, system, although the Orders are not founded upon them, yet the characters of genera, and sometimes of large tribes, are derived from them: and as they appear less liable to variation than almost any other organ, as Mr. W. S. MacLeay has judiciously observed, there seems good reason for employing them--it is therefore of importance that you should be well acquainted with them.

Their situation is usually below each mandible, on each side of the labium; towards which they are often somewhat inclined, so that their tips meet when closed. In some cases, as in the Predaceous beetles (Carabus L. &c.), they exactly correspond with the mandibles; but in others their direction with respect to the head is more longitudinal, as in the Hymenoptera, &c. In substance they may be generally stated to be less hard than those organs; yet in some instances, as in the Libellulina, Anoplognathidæ, &c. they vie with them, and in the Scarabæidæ and Cetoniadæ exceed them, in hardness. In the bees, and many other Hymenoptera, they are soft and leathery. Their articulation is usually by means of the hinge on which they sit: it appears entirely ligamentous, and they are probably attached to the labium at the base, or mentum--at least this is evidently the case with the Hymenoptera, in which the opening of the maxillæ pushes forth the labium and its apparatus. In that remarkable genus related to the glow-worms, now called Phengodes (Lampyris plumosa F.), and in the case-worm flies (Trichoptera K.), the maxillæ appear to be connate with the labium, or at least at their base.--As to their composition, these organs consist of several pieces or portions. At their base they articulate with a piece more or less triangular, which I call the hinge (Cardo)[1262]. This on its inner side is often elongated towards the interior of the base of the labium, to which it is, as I have just observed, probably attached. This elongate process of the hinge in Apis, Bombus, &c. appears a separate articulation; and the two together form an angle upon which the mentum sits[1263], and by this the maxilla acts upon the labial apparatus.

The next piece is the stipes or stalk of the maxilla. This is the part that articulates with the hinge, and may be regarded in some cases, as in the Orthoptera &c., as the whole of the maxilla below the feeler; and in others, as in the Geotrupidæ, Staphylinidæ &c., as only the back of it, the inside forming the lower lobe. This piece is often harder and more corneous than the terminal part, is linear, often longitudinally angular, and in the bee-tribes (Apis L.) is remarkable on its inner side for a series of bristles parallel to each other like the teeth of a comb[1264]. In Pogonophorus Latr., a kind of dor or clock-beetle, it is armed on the back with four jointed spines, the intermediate one being forked[1265]. M. Latreille has thus described the stipes of the maxillæ of Coleoptera: "Next comes the stalk," says he, "which consists of three parts: one occupies the back and bears the feeler; the second forms the middle of the anterior face, and its figure is triangular; the third fills the posterior space comprised between the two preceding; and is that which is of most consequence in the use of the maxilla; the anterior feeler, where there are two, the galea, and the other appendages that are of service in deglutition, are part of that piece[1266]."

The third and terminal portion of the maxilla is formed by the lobe, or lobes (Lobi). This may be called the most important part of the organ, since it is that which often acts upon the food, when preparing for deglutition. When armed with teeth or spines at the end, its substance is as hard as that of the mandibles; but when not so circumstanced, it is usually softer, resembling leather, or even membrane[1267]; and sometimes the middle part is coriaceous, and the margin membranous. This part is either simple, consisting only of one lobe, as you will find to be the case with the Hymenoptera, Dynastidæ, Nemognatha, and several other beetles; or it is compound, consisting of two lobes. In the former case, the lobe is sometimes very long, as in the bee tribes, and the singular genus of beetles mentioned above[1268], Nemognatha; and at others very short, as in Hister, &c. The bilobed maxillæ present several different types of form. Nearest to those with one lobe are those whose lower lobe is attached longitudinally to the inner side of the stalk of the organ, above which it scarcely rises. Of this description is the maxilla in the common dung-beetle (Geotrupes stercorarius), and rove-beetle (Staphylinus olens).[1269] Another kind of formation is where the lower lobe is only a little shorter than the upper: this occurs in a kind of chafer (Macraspis tetradactyla MacLeay).[1270] A third is where the upper lobe covers the lower as a shield; as you will find in the Orthoptera order, and the Libellulina, and almost in Meloe[1271]. A fourth form is where the upper lobe somewhat resembles the galeate maxilla just named; but consists of two joints. This exists in Staphylinidæ, &c.[1272] The last kind I shall notice is when the upper lobe not only consists of two joints, but is cylindrical, and assumes the aspect of a feeler or palpus[1273]. This is the common character of almost all the Predaceous beetles (Entomophagi Latr.). This lobe, which has been regarded as an additional feeler, is strictly analogous to the upper lobe in other insects, and therefore should rather be denominated a palpiform lobe than a palpus. Where there are two lobes, the upper one is most commonly the longest; but in many species of the tribe last mentioned the lower one equals or exceeds it in length[1274].

The lobes vary in form, clothing, and appendages. The upper palpiform lobe in those beetles just mentioned, in general varies scarcely at all in form; but the genus Cychrus (which is remarkable for a retrocession from the general type of form of the Carabi L. making an approach towards that of those Heteromera which, from their black body and revolting aspect, Latreille has named Melosomes,) affords an exception, the upper joint being rather flat, linear-lanceolate, incurved, and covering the lower lobe[1275], which it somewhat resembles. The lower lobe also in this tribe varies as little as the upper, being shaped like the last joint of that lobe in Cychrus just described, except that in Cicindela it is narrowest in the middle[1276]. In other tribes the upper valve is sometimes linear and rounded at the apex, and the lower truncated, as in Staphylinus olens[1277]; sometimes the upper one is truncated or obtuse, and the lower acute, as in Trogosita and Parnus[1278]. In Ptinus, another tribe of beetles, before noticed as injurious to our museums[1279], the reverse of this takes place, the upper-lobe, which is the smallest and shortest, being acute, and the lower truncated[1280]. In Blaps both are acute[1281]. In Rhipiphorus and Scolytus the lobes are nearly obsolete. The lower lobe is bifid in Languria, a North American genus of beetles, so as to give the maxilla the appearance of three lobes[1282]; and in Erotylus, a South American one, the upper is triangular[1283]: it is often oblong, quadrangular, linear, &c. in others.--In those that have only one lobe the shape also varies. In Gyrinus, the beetle that whirls round and round on the surface of every pool, which, though it belongs to the Predaceous tribe, has only one lobe, the lobe represents a mandible in shape of the laniary kind, being trigonal and acute[1284]; and in the Anoplognathidæ, a New Holland tribe of chafers, in which it is, as it were, broken, the lobe forming an angle with the stalk, it is concavo-convex and obtuse, and somewhat figures a molary tooth[1285]. In the first tribe into which the bees (Apis L.) have been divided (Melitta Kirby), the lobe is often linear or strap-shaped, and bifid at the apex; and in the second (Apis K.) lanceolate and intire[1286]. In Cerocoma it is long and narrow[1287]. More variations in form might be named, but these are sufficient to give you a general idea of them in this respect. With regard to their clothing, I have not much to observe--in examining the Predaceous beetles you will observe, that the interior margin of the lower incurved lobe is fringed with stiff bristles or slender spines, and in many other beetles either one or both lobes have a thick coating or brush of stiffish hairs[1288]; but in several cases only the apex of the lobe is hairy. In the Orthoptera order, and many of the Melolonthidæ or chafers, the whole maxilla is without hairs, or nearly so.

The appendages of the maxillæ are next to be noticed. These are principally their claws, or laniary teeth; for they are seldom armed with incisive or molary teeth. The whole tribe of Predaceous beetles, with few exceptions, have the inner lobe of their maxilla armed with a terminal claw, which in the Cicindelidæ articulates with the lobe, and is moveable, but in the rest of the tribe is fixed[1289]. In Phoberus MacLeay the lower lobe has two spines[1290]. In Locusta this lobe has three or four spines or laniary teeth, and in Æshna there are six, which, like the claw of Cicindela, are moveable[1291]. In others both lobes terminate in a single spine or claw: this is the case with Paxillus MacLeay[1292]. In Passalus, nearly related to the last genus, the upper lobe is armed with a single spine, and the lower one with two[1293]. Those maxillæ that terminate in a single lobe are also often distinguished by the spines or teeth with which it is armed; thus in a nondescript chafer belonging to the Dynastidæ (Archon K. MS.) it terminates in two short teeth; in that remarkable Petalocerous genus Hexodon Oliv. in three truncated incisive ones[1294]; in Dynastes Hercules in three acute spines[1295]. Four similar ones arm the apex of the maxilla in that tribe of Rutelidæ which have striated elytra; and five that are stout and triquetrous those of Melolontha Stigma F. Many others have six spines, sometimes arranged in a triple series[1296]. Besides teeth or spines, in some cases the lobes of maxillæ terminate in several long and slender laciniæ or lappets fringed with hairs. At least those of a Leptura (L. quadrifasciata L.) described by De Geer, appear to be thus circumstanced. He conjectures that this beetle uses its maxillæ to collect the honey from the flowers[1297].

As the principal use of the mandibles is cutting and masticating, so that of the organs we are considering seems to be primarily that of holding the food and preventing it from falling while the former are employed upon it. I say this is their primary use; for I would by no means deny that they assist occasionally in comminuting or lacerating it. In fact, were there no organs appropriated to this use, and if both mandibles and maxillæ were employed at the same time in comminuting the food, it seems to me that it must fall from the mouth. In a large proportion of insects the lobes of the maxillæ are not at all calculated for laceration or comminution; and in those tribes--as the Melolonthidæ, Rutelidæ, Dynastidæ--in which they seem most fitted for that purpose, the mandibles have incisive teeth at their apex, and at their base a powerful mola or grinder: circumstances which prove, that even in this case the business of mastication principally devolves upon them.

6. Palpi Maxillares[1298]. There is one circumstance that particularly distinguishes the maxillæ from the mandibles--they are palpigerous, as well as the under-lip. The feelers, or palpi, emerge usually from a sinus observable on the back of the maxillæ where the upper lobe and stalk meet. Their articulation does not materially differ from that of the labial palpi. Each maxilla has properly only one feeler; but, as was lately observed[1299], in certain tribes the upper lobe is jointed and palpiform, which has occasioned it to be considered as a feeler, and these tribes have been regarded as having six feelers. The most general rule with regard to the length of the palpi is, that the maxillary shall be longer than the labial; but the reverse often takes place. In many bees the maxillary consist only of a single joint, and are very short; while the labial consist of four, and are very long[1300]: and in some insects (as in Pogonophorus Latr.) the four palpi are of equal length[1301]. The antennæ are most commonly longer than the palpi; but in several aquatic beetles, as Elophorus, Hydrophilus, &c., whose antennæ in the water are not in use, the organs we are considering are the longest.--As to the number of their articulations, it varies from one to six; which number they are not known to exceed. In each of the Orders a kind of law seems to have been observed as to the number of joints both in the maxillary and labial palpi, but which admits of several exceptions. Thus in the Coleoptera, the natural number may be set at four joints for the maxillary, and three for the labial palpi: yet sometimes, as in Stenus, Notoxus, &c., the former have only three joints, and the latter, as in Stenus and Tillus, only two. In the Orthoptera the law enjoins five for the maxillary, and three for the labial; and to this I have hitherto observed no exception. In the Hymenoptera, the rule is six and four, but with considerable exceptions, especially as to the maxillary palpi, which vary from six joints to a single one: thus in the hive-bee and the humble-bee, the labials, including the two flat joints or elevators, have four joints, while the maxillaries are not jointed at all[1302]. In Chrysis, in which the latter consist of five, the former are reduced to three. The Libellulina may almost be regarded as having no maxillary palpi, since they exhibit no organ that is distinctly palpiform. It seems to me that the upper lobe of their maxilla, which articulates with the stalk in the same manner as a feeler, may be regarded as an instance in which that lobe and the feeler coalesce into one; and the mucro that proceeds from the lobe has the aspect of an emerging feeler, and corresponds somewhat with the labial one above noticed[1303]. In the remainder of the Neuroptera and the Trichoptera, the prevailing number is five and three. In the latter there are exceptions, which will furnish good characters for genera. In the Lepidoptera we find two, and sometimes three, the maxillary being very minute[1304]. The Diptera Order presents two tribes in this respect quite distinct from each other. The most natural number of joints in the maxillary palpi of the Tipulidæ, Culicidæ, &c. is four or five: the last joint, however, in Tipula, Ctenocera, &c. like that of the antennæ in Tabanus L., appears to consist of a number of very minute joints[1305]; but in the Asilidæ and Muscidæ, &c., the number two seems to be most prevalent[1306]. The labial palpi in this order are obsolete.--As to shape, the maxillary palpi, as well as the labial, are usually filiform; but in the weevil tribes (Curculio L.) they are most commonly very short and conical[1307]; in the chafers (Scarabæus L.) they usually are thickest at the apex[1308]; in Megachile and Euglossa, wild bees, they are setaceous, growing gradually more slender from the base to the summit[1309]: a tribe of small water-beetles (Haliplus), the saw-flies (Tenthredo L.), and several other Hymenoptera, have them thickest in the middle[1310]. Their most important part, however, and that which varies most in form, is the terminal joint:--of this I have already related some singular instances[1311], and shall now describe a few more. This joint is sometimes acute, at others blunt, at others truncated: in figure it is ovate, oblong, obtriangular, hatchet-shaped, lunate, transverse, conical, mammillate, subulate, branched, chelate, laciniate, lamellate, &c. &c.[1312]: terms which I shall more fully explain to you hereafter, and which I only mention here to show the numerous variations as to figure, of which this joint exhibits examples. The palpi in general at their vertex are often rather concave; and this concavity is formed by a thin papillose membrane, which it is supposed the animal has the power of pushing out a little, so as to apply it to surfaces. The primary use of the palpi of insects will be considered when I treat of their senses; but they probably answer more purposes than one. For instance, when I was once examining, under a lens, the proceedings of a species of Mordella, which was busily employed in the blossom of some umbelliferous plant, it appeared to me to open the anthers with its maxillary palpi, and they often held the anther between them: when not so employed, they were kept in intense vibration, more than even its antennæ; and at the same time, as far as I could judge, an Elater made the same use of them.

7. Lingua[1313].--This name was applied by Linné to the part in insects representing the tongue in vertebrate animals; and as it performs most of the common offices of a tongue, and the pharynx is situated with respect to it, as we shall presently see, nearly as it is in those animals, there seems no more reason for giving it a new name, than there is for giving a new name to the head or legs of insects, because in some respects they differ from those of the higher animals. I shall not therefore call it Ligula, with Fabricius and Latreille, nor Labium, with Cuvier and others, but adhere to the original term, which every one understands.

The tongue lies between the two lips--the labrum and labium. On its upper side, at the base, it meets the palate or roof of the mouth, below which it is attached, it may be presumed, by its roots to the crust of the head, on each side the pharynx or swallow; and on its lower side, in many cases, it is attached to the labium, and that very closely, so as to appear to be merely a part of it, and to form its extremity: but in the Orthoptera and Libellulina, it is more free, and in form somewhat resembling the tongue of the quadrupeds[1314].--In substance the tongue varies. In general it seems something between membrane and cartilage; but in the Predaceous beetles, in which it is not covered by the labium, it approaches nearer to the substance of the general integument, and in Anthia F. it is quite hard and horny:--that just mentioned of the Orthoptera and Libellulina is more fleshy[1315]. With regard to its station, in many cases, as in the instance just named, in the Lamellicorn tribe (Scarabæus L.) and others, it is, when unemployed, concealed within the mouth; the lips, mandibles, and maxillæ all closing over it. The tongue of some Hymenoptera also is retractile within the mouth. "When ants are disposed to drink," says M. P. Huber, "there comes out from between their lower jaws, which are much shorter than the upper, a minute, conical, fleshy, yellowish process, which performs the office of a tongue, being pushed out and drawn in alternately: it appears to proceed from the lower-lip.--This lip has the power of moving itself forwards in conjunction with the lower jaws: and when the insect wishes to lap, all this apparatus moves forward; so that the tongue, which is very short, does not require to lengthen itself much to reach the liquid[1316]." M. Lamarck thinks that the labium of insects has a vertical motion (de haut en bas ou de bas en haut)[1317]. This it certainly has in some degree; but it has also, as in the above case, a more powerful horizontal one, which is produced, in Hymenoptera at least, by the opening of the maxillæ--as I have already observed[1318].

I have little to say with respect to the structure of the tongue: it generally seems to be without articulations; but in many bees it articulates with the labium where it enters it, so as when unemployed to form a fold with it. In the hive-bee it terminates in a kind of knob or button, which has been falsely supposed to be perforated for imbibing the honey by suction. The upper part of this tongue is cartilaginous, and remarkable for a number of transverse rings: below the middle, it consists of a membrane, longitudinally folded in inaction, but capable of being inflated to a considerable size: this membranous bag receives the honey which the tongue, as it were, laps from the flowers, and conveys it to the pharynx[1319]. In Stenus this organ is retractile, and consists of two joints[1320].

The shape of the tongue of insects probably varies as much as any other part; but as it is apt to shrink when dried[1321], and is not easy to come at, we know but little of its various configurations:--in the bees it is very long, in most other insects very short. Though frequently simple and undivided, in many cases it presents a different conformation. Thus in the saw-flies (Tenthredo L.) it terminates in three equal lobes[1322]; in Stomis and Geotrupes in three unequal ones, the intermediate being very short[1323]; in Carabus, in three short teeth[1324]; in Pogonophorus it represents a trident[1325]; in the wasp it is bifid, each lobe being tipped with a callosity[1326]; in Melolontha Stigma it is bipartite[1327]; in Elaphrus, the analogue of the tiger-beetles, it terminates in a single tooth or point; in the aquatic beetles, Dytiscus L., it is quadrangular and without teeth[1328]; in some Ichneumonidæ it is concavo-convex, and forms a demitube; and in others it is nearly cylindrical[1329].

In many insects it has no hairs, but in the Predaceous beetles it generally terminates in a couple of bristles[1330]. In the hive- humble- and other bees, it is extremely hairy[1331]; a circumstance which probably enables it more effectually to despoil the flowers of their nectar. In Geotrupes stercorarius, the common dungchafer, and Melolontha Stigma lately mentioned, the lobes of the tongue are fringed with incurved hairs[1332]; and in Æshna it is hairy on the upper side, each hair or bristle crowning a minute tubercle. In many cases the tongue is attended, and sometimes sheathed at the base, by two usually membranous appendages:--these the learned Illiger has denominated paraglossæ; and I shall adopt his term. You will find them frequently attached to the tongue of the Predaceous beetles[1333], and to that of many Hymenoptera. In the hive-bee and humble-bee they are short, and take their origin within the labial feelers[1334]: in Euglossa, another bee, they are long, involute at the tips, and, what is not usual with them, very hairy[1335]: in the wasp, like the lobes of the tongue, they are tipped with a callosity.

Under this head I may observe to you, that the insects whose oral organs we are considering besides a tongue appear likewise to be furnished with a palate (Palatum). This, though a part of the roof of the mouth, is not precisely in the situation of the palate of vertebrate animals, since it seems rather the internal lining of the labrum. If you take the common dragon-fly (Æshna viatica), you will find that the under side of this part and of the rhinarium is lined with a quadrangular fleshy cushion, beset, like the upper surface of the tongue, with minute black tubercles, crowned with a bristle. This cushion is divided transversely into two parts by a depression; the anterior or outer piece being attached to the labrum, and the other piece to the rhinarium. The former has a central longitudinal cavity, black at the bottom, on the sides of which the tubercles are flat and without a bristle. From its base on each side a spiniform process emerges, forming a right angle with it. These processes seem the antagonists of those mentioned above[1336], that emerge from the labium. The posterior or inner piece has on each side a roundish space, attached to the under surface of the two sides of the rhinarium, beset also with bristle-bearing tubercles. You will find something similar lining the labrum and nasus of some Coleoptera,--say Geotrupes, Necrophorus, and Dytiscus. The first piece I regard as the analogue of the palate, and the second as connected with the sense of smelling. In Necrophorus the circular pieces are covered with a finely striated membrane, and in Dytiscus each has a little nipple.

8. Pharynx[1337].--On the upper side of the tongue, usually at its base or root, is the pharynx, or aperture by which the food passes from the mouth to the œsophagus. This orifice, which is situated with respect to the tongue of the Orthoptera and Libellulina nearly as in those insects (at least as far as I have been able to examine them), whose tongue is called a ligula or labium,--of course exists in all the mandibulate Orders whose mouth we are now considering. In the Hymenoptera it is covered by a valve, the Epipharynx of Savigny; and it appeared to me to be so likewise in one of the Harpalidæ that I examined. The formation seems different in Geotrupes, as far as I can get an idea of it; but it is so difficult to examine the interior of the mouth without laceration of some of the parts, that I can only tell you what the appearances were in one instance, upon removing the labrum from the mandibles; and in another, separating the whole apparatus of the labium, including the maxillæ, from the mandibles and labrum. In the former case, the mandibles coincided at the base, the two molary plates (molæ), which in this genus are narrow, transverse and not furrowed, are so applied as evidently to have an action upon each other, as the mandible opens and shuts, proper for trituration. Within these is the base of the tongue, under the form of a ventricose sack. The upper part of this last organ, which forms the internal covering of the labium, appears to consist of three (in the recent insect fleshy) lobes, the middle one being bent downwards internally, so as to form a kind of sloping cover to an orifice in the part I call the base. After two or three days, the tongue shrinks and dries to a hard substance;--between the mandibles and the base of the tongue I could not discover the pharynx. The above apparent opening covered by the tongue was the only one I could perceive. In the latter case, the form and structure of the base of the tongue is more visible: it is an oblong ventricose tubular sack, projecting above anteriorly into an acute angle formed by a fine white membrane, most beautifully and delicately striated with oblique striæ, to be seen only under a powerful lens: on the anterior side of this sack are two parallel cartilaginous ridges close to each other, fringed with short hairs, which take their origin from the angle. I could not be certain whether the orifice covered by the intermediate lobe was only apparent, or real; but I did not succeed in my endeavour to find any other pharynx, though from the molary structure of the base of the mandibles one may conjecture that there must be one situated at the base of this sack to receive the food they render after trituration. The excrement of this animal is not fluid. In the Libellulina the pharynx seems closed by two valves meeting. This part in Hymenoptera, and probably in other Orders, has the aspect of being cartilaginous and fitted to sustain the action of the substances that have to pass through it[1338].

The Epipharynx is a valve, called by M. Latreille sublabrum (sous labre[1339]), attached by its base to the upper margin of the pharynx, or that next the labrum. In the bees it is said by Reaumur to be of a fleshy substance, and capable of changing its figure. He seems to think it the real tongue of the bee[1340]; but as it does not appear to have any of the uses of a tongue, and merely closes the orifice of the mouth, it surely does not merit that name. M. Savigny calls it a membranous appendage which exactly closes the pharynx[1341]. De Geer has examined the epipharynx of the wasp, which he describes as of a scaly substance, and regards merely as the cover of the part just named[1342].

With regard to the Hypopharynx, which Latreille considers as a support and appendage of the epipharynx, I have little to add to the definition I have given of it above. In the Libellulina the base of the tongue terminates towards the pharynx in a fleshy cushion, armed at each angle next to that part with a short hard horn or tooth of a black colour. This cushion, I suppose, may be analogous to the hypopharynx of M. Savigny[1343]. On the opposite side the pharynx is closed by another fleshy cushion (epipharynx?), which appears to line the nose, behind those two mammillæ before described[1344], which form the internal covering of the rhinarium.

Before I call your attention to what I would denominate an imperfect mouth, in which some one or more of the seven organs above enumerated exist under another form, or only as rudiments,--I must say something upon the mouth of the Myriapods and Arachnida, in which there seem to be redundant organs of manducation.--M. Latreille, in the Essay lately quoted, in which, though some of his notions seem fanciful, he has shown a vast depth and range of thought and research, has asserted,--from the admirable and curious observations of M. Savigny, and those which since their publication he has made himself,--that the masticating organs of annulose animals (called by him condylopes) are a kind of legs[1345]. And M. Savigny, whose indefatigable labours and unparalleled acuteness have opened the door to a new and vast field in what may be denominated analogical anatomy,--has observed, that with certain Apiropods[1346] the organs that serve for manducation do not differ essentially from those which, with the other Apiropods and the Hexapods, serve for locomotion[1347]: and the unguiform mandibles of the larvæ of certain Diptera, you have before been told, are used not only in manducation, but also as legs[1348]. These remarks will satisfactorily prove to you, that organs which at first sight possess no visible affinity or analogy--as for instance, jaws and legs--may, if traced through a long series of beings, exhibit a very great one;--and will lessen your surprise when you find, that in certain tribes such commutations of organs and their use take place.

The following is the structure, as to its organs, of the mouth of the myriapods, as exhibited by the centipedes (Scolopendridæ). The part which appears to perform the office of the upper lip (but which M. Savigny regards as the nose, calling it the chaperon,) is a transverse piece with a deep anterior sinus, in the centre of which is a minute tooth[1349]. This piece is separated from the forepart of the head by a suture; but it probably is not moveable: however, it covers the mouth, and may be regarded rather as analogous to the labrum. Below this are two mandibles, armed at their end with five sharp triangular teeth[1350], under which are the maxillæ, terminating in a moveable concavo-convex lobe, resembling the valve of a bivalve shell[1351]; and between them is the labium, of a rhomboidal shape, divisible into two lobes, attached laterally to the maxillæ: these lobes M. Savigny terms the second maxillæ, forming with the others, according to him, the labium[1352]. Affixed to the base of this labium, or covering it on the outside, are a pair of pediform palpi, which he considers as the first auxiliary labium, and representative of the first pair of legs of hexapods and Iuli[1353]. I imagine them to be also the analogues, in some degree, of the labial palpi of a perfect mouth. The last of the organs in question is a large rhomboidal plate affixed to the first apparent segment of the trunk, crowned at its vertex with two truncated denticulated teeth, and from the upper sides of which emerge a pair of moveable organs terminating in a powerful incurved claw, and which entirely covers all the other parts of the mouth[1354]. This, M. Savigny deems as a second auxiliary labium, and the lateral organs of prehension,--which may be regarded each as a kind of maxillary hand, and as the only representatives in this tribe of the maxillary palpi, though widely different,--he looks upon as really analogous to the second pair of legs in Iulus and the hexapods[1355]. These two pairs of pedipalpes (to use an expressive French term) show their relation to legs by their general structure, and their analogy with palpi by their use as oral organs, though belonging to the trunk: so that here we see the legs and their appendages assume a material function in manducation, forming a singular contrast to what we had observed before with regard to mandibles becoming instruments of locomotion. The mouth of the Iulidæ, with little variation, is upon the same plan[1356] with those here described.

The next type of form with regard to the oral organs is that of the Arachnida. In these, as you know, the head is confounded with the trunk; so that they are a kind of Blemmyes in the insect world. Their organs of manducation, amongst which there is no labrum or upper lip, are, in the first place, a pair of mandibles planted close and parallel to each other in the anterior part of the head, which they terminate. In the spiders they consist of two tubular joints, of which the first is much the largest, more or less conical or cylindrical, and armed underneath with a double row of stout teeth; and the terminal one is more solid and harder, in the form of a very sharp crooked claw, which in inaction is folded on the first joint between the teeth. Under its extremity on the outside is a minute orifice, destined to transmit a venomous fluid, which is conducted there by an internal canal from the base of the first joint, where is the poison-bag[1357]. In the scorpion and harvest-man (Phalangium) the mandible consists of two joints terminated by a chela or double claw, the exterior one being moveable[1358].--M. Latreille, as has been before observed, regards these not as representatives of the mandibles of hexapods, but as replacing the interior pair of antennæ, in the situation of which they are precisely placed, of the Crustacea[1359]: and M. Savigny is of opinion that the Arachnida may in some sort be defined as Crustacea without a head, and with twelve legs, of which the two first pair are converted into mandibles and maxillæ[1360]. From the situation of the organs in question, the first of these opinions seems preferable; but the conversion of the legs in other cases, at least the coxæ, into organs of manducation, gives some weight to the last. With regard to their use, it is said to be to retain the insect which the animal has seized, and to facilitate the compression which the maxillæ exercise upon it for the extraction of the nutritive matter[1361]. If this be correct, in this respect the mandibles may be said to represent the maxillæ of the mandibulate hexapods; and, vice versa, the sciatic maxillæ, as they have been denominated[1362], of the Arachnida, their mandibles. The palpi are pediform, and the first joint of the coxa, or hip, acts the part of a maxilla:--this is composed of a single piece or plate, more or less oval or triangular, sometimes straight and sometimes inclined to the labium, with the interior extremity very hairy. The labium consists also of a single piece, and is only an appendage of the anterior extremity of the breast. The interior of the mouth, or palate, presents a fleshy, hairy, linguiform piece, which is usually applied to the internal face of the labium. An opening is supposed to exist in its sides, for the transmission of the alimentary juices[1363]. If you examine the under side of the body of a scorpion, you will find that not only the palpi, but the two anterior pair of legs, by means of their coxæ, are concerned in manducation: so that these insects have in fact three pairs of maxillæ--a circumstance that M. Savigny has observed to take place also in the harvest-men (Phalangium L.)[1364]. The palpi of the scorpion, which may be called its hands, like the anterior legs of the lobster and crab, terminate in a tremendous chela or forceps, consisting of a large triangular joint, armed at the end with a double claw internally toothed; the exterior one of which, contrary to what takes place in the animals just named, is moveable, and not the interior[1365].

* * * * *

Having given you this full account of the trophi of those animals that have all the organs of manducation developed, I must next advert to those in which one part receives an increment at the expense of others, and the whole oral machine is fitted for suction; or where some parts appear to be deficient, so that this may be called an imperfect mouth. At first sight one would regard the trophi of a bee as of this description; but this is not the case, since it has all the ordinary organs, though the tongue is unusually long, and looks as if it was made for suction; which, however, as you have been informed, is not the case.

There are five kinds of imperfect mouth to be met with in insects that take their food by suction, each of which I shall distinguish by a separate denomination. The first is that of the Hemiptera Order:--this I term the Promuscis; the second is that of the Diptera, which with Linné I call Proboscis; the third, peculiar to the Lepidoptera, is with me an Antlia; the fourth, which I name Rostrulum, is confined to the Aphaniptera order, or genus Pulex L.; and the last is Rostellum, which I employ to denote the suctory organs of the louse tribe (Pediculidæ).

i. Promuscis[1366].--The organ we are first to consider has usually been denominated Rostrum: but since that term is likewise in general use for the snout of insects of the weevil tribes (Curculio L.), I think you will concur with me in adopting the one here proposed, for the very different oral instruments of the Hemiptera. Illiger has employed promuscis to denote those of bees[1367]: but since, as I have just observed, they consist of all the ordinary organs, they seem to require no separate denomination: the term, therefore, may be applied to represent a different set of trophi, without any risk of producing confusion. This part consists of five pieces: viz. a minute, long, conical piece, commonly very slender, which covers the base of the promuscis, and represents the labrum[1368]; a jointed sheath (vagina), consisting of either three or four joints, the analogue of the labium, and four slender rigid lancets (scalpella), the two exterior ones, according to M. Savigny, representing the mandibles, and the intermediate pair the maxillæ[1369]. By the union of these four pieces a suctorious tube is formed, which the animal inserts into the substance, whether animal or vegetable, the juices of which form its nutriment. These pieces are dilated at their base, and serrated at their apex; and the two central ones, though at their origin they are asunder, form one tube, which has often been mistaken for a single piece. A pharynx and tongue have been discovered by M. Savigny in this apparatus; who thinks that in Nepa there are also rudiments, but very indistinct, of labial palpi: so that the maxillary palpi seem to be the only part absolutely wanting[1370].

The Promuscis when at rest is usually laid between the legs; but when employed, in most cases its direction is outward. In the genus Chermes L. (Psylla Latr.) the origin of the promuscis has been supposed to be in the breast; but if closely examined, this anomaly in nature will be found not to exist. If you take one of these insects, the first thing that strikes you upon inspecting the head, is a pair of remarkable conical processes into which the front appears to be divided. Look below these, and you will there discover the upper-lip: and from this you may follow the promuscis till it gets beyond the forelegs, when it takes a direction perpendicular to the body[1371]; a circumstance which has given rise to the above false notion. Though in Coccus, Chermes, &c. this instrument is short, in some Aphides it is longer in proportion than in any other insect. In A. Quercus it is three times the length of the body; so that when folded, it stretches out beyond it, and looks like a long tail[1372]; and in A. Abietis it even exceeds that length[1373].

ii. Proboscis[1374].--Linné long since, and after him Fabricius, has employed this term to designate the oral instruments, or rather their sheath, in the Muscidæ and some others, calling the same organ, when without fleshy lips, rostrum and haustellum: but as the parts of the mouth in all true Diptera (for Hippobosca and its affinities can scarcely be deemed as co-ordinate with the rest), are analogous to each other; although in some they are stiff and rigid, in others flexile and soft, and in Œstrus (except the palpi) mere rudiments,--the same appellation ought to designate them all. I am happy to find that M. Latreille agrees with me in this opinion; and to his sensible observations on this head, if you wish for further information, I refer you[1375]. The mouth of Dipterous insects appears to vary in the number of pieces that it presents; but in all, the theca or sheath is present, which represents the labium (including the mentum) of the mandibulate Orders[1376]. It consists of three joints, the last of which is formed by the liplets (Labella). Those in the Muscidæ are large, turgid, vesiculose, and capable of dilatation; in the Bombylidæ and other tribes they are small, slender, long and leathery, and sometimes recurved. The second joint or stalk, which may be said to represent the mentum, the liplets being properly in a restricted sense the analogue of the labium, its sides being turned up, forms a longitudinal cavity, which contains the haustellum. The upper piece of this, the valvula, is long, rigid, and very sharp, representing the labrum[1377]. Beneath this cover, in the above cavity, are the lancets; which, as far as they are at present known, vary in number and form: sometimes there are five of them, sometimes four, sometimes two, and sometimes, it should seem, only one[1378]. In the gnat (Culex) they are finer than a hair, very sharp, and barbed occasionally on one side[1379]; in the horse-fly (Tabanus L.) they are flat and sharp like the blade of a knife or lancet[1380]. In this tribe the upper pair, or the knives (Cultelli), represent the mandibles; the lower pair, or the lancets (Scalpella), usually palpigerous, the maxillæ; and the central one the tongue. In the horse-fly Reaumur has figured only four, exclusive of the labrum and labium; but in a specimen I have preserved there appear to be five, one of which, as slender as a hair, I regard as the analogue of the tongue[1381].--When the lancets are reduced to two, they probably represent the maxillæ, the mandibles being absorbed in the labrum; and where there is only one, the maxillæ also are absorbed by the labium, which then bears the palpi, the lancet representing the tongue[1382]. The lancets are so constructed in many cases, as to be able by their union to form a tube proper for suction, or rather for forcing the fluid by the pressure of the lower parts to the pharynx[1383]. Labial palpi appear not usually present in the proboscis; but M. Savigny thinks he has discovered vestiges of them in Tabanus[1384]. In this genus the maxillary ones are large, and consist of two joints[1385]. The proboscis is often so folded, as to form two elbows; the base forming an angle with the stalk, and the latter with the lips, so as in shape to represent the letter Z, only that the upper angle points to the breast, and the lower one to the mouth: this is the case with the flesh-fly and many others. In other flies, as Conops and Stomoxys, whose punctures on our legs so torment us[1386], there is only a single fold, with its angle to the breast. The proboscis is received in a large oblong cavity of the underside of the anterior part of the head.

It may here be observed, that in the promuscis the elongation of the organs seems to be made chiefly at the expense of all the palpi, but in the proboscis at that of the labial only; and in some cases at that also of the mandibles or maxillæ;--the former merging in the labrum and the latter in the labium.

iii. Antlia[1387].--The third kind of imperfect mouth is that of the Lepidoptera, which I have called Antlia. Fabricius denominates it lingua: but as this organ has no analogy with the real tongue of insects, this is confessedly improper, and it appeared necessary therefore to exchange it for another denomination: I have endeavoured to apply a term to it that indicates its use--to pump up, namely, the nectar of the flowers into the mouth of the insect. On a former occasion I described to you the structure of this instrument[1388]; but further discoveries with regard to it having since been made by MM. Savigny and Latreille, I shall here give you the result of their observations. The former of these able physiologists has detected in the mouth of the Lepidoptera rudiments of almost all the parts of a perfect mouth. Of the correctness of this assertion you may satisfy yourself, if you consult his admirable elucidatory plates, and compare them with the insects. Just above the origin of the spiral tongue or pump, the head is a little prominent and rounded; and immediately below the middle of this prominence there is a very minute, membranous, triangular or semicircular piece; which from its position, as covering the base of the antlia, may be regarded as the rudiment of the upper-lip (labrum)[1389]. On each side of the outer base of the antlia is another small immoveable piece, resembling a flattened tubercle, the end of which is internally hairy or scaly: these pieces appear to represent the mandibles[1390]. Near the base of each half of the antlia, just below a sinus, may be distinctly seen the minute, usually biarticulate rudiment of a maxillary palpus[1391]; demonstrating to a certainty that these spiral organs, at least their lateral tubes or Solenaria, are real maxillæ[1392]. The rudiment of the under-lip (Labium) is the almost horny triangular piece united by membrane to the two stalks of the maxillæ, and supporting at its base the recurved labial palpi; which are so well known that I need not enlarge upon them[1393]. Amongst these parts there seems at first sight no representative of the tongue; but M. Latreille has advanced some very ingenious, and I think satisfactory arguments[1394], which go to prove that this part, at least the tongue of Hymenoptera, has its analogue in the intermediate tube or Fistula formed by the union of the two maxillæ, and which conveys the fluid aliment of this Order to the pharynx. As in Diptera the maxillæ sometimes merge in the labium, so here the tongue (as it were divided longitudinally) merges in the maxillæ. He further observes, that in a transverse section of the maxilla of the death's-head hawk-moth (Sphinx Atropos), the lateral tube appeared to be divided into two by a membranous partition, and to contain in the upper cavity a small cylindrical tube, which seemed to be a trachea[1395]. To animals that are without lungs, and breathe by tracheæ, suction must be performed in a very different way from what it is by those that breathe by the mouth: and as in the very extended organs in question the fluid has a long space to pass before it reaches the pharynx, in some way or other these lateral tubes may have the power of producing a vacuum in the middle tube, and so facilitate its passage thither. We see, in the antlia, that the maxillæ receive their vast elongation at the expense of all the other organs, except the labial palpi.

iv. Rostrulum[1396].--An animal very annoying to us affords the type of the next kind of imperfect mouth--I mean the flea. Its oral apparatus, which I would name rostrulum, appears to consist of seven pieces. First are a pair of triangular organs, the laminæ, which together somewhat resemble the beak of a bird, and are affixed, one on each side of the mouth, under the antennæ: these represent the mandibles of a perfect mouth[1397]. Next, a pair of long sharp lancets (Scalpella), which emerge from the head below the laminæ: these are analogous to maxillæ[1398]: a pair of palpi, consisting of four joints, are attached to these near their base[1399], which of course are maxillary palpi. And lastly, in the midst of all is a slender setiform organ (ligula), which is the counterpart of the tongue[1400]. Rösel, and after him Latreille, seem to have overlooked this last piece, since they reckon only six pieces in the flea's mouth[1401]: but the hand and eye of our friend Curtis have detected a seventh, as you see in his figure. From this account it appears, that the elongation of the organs of the Aphaniptera Order is at the expense of the labium and its palpi.

v. Rostellum.--So little is known of the composition of the next kind of imperfect mouth, that I need not enlarge upon it. It is peculiar to the louse tribe (Pediculidæ), and it consists of the tubulet (Tubulus), and siphuncle (Siphunculus). The former is slenderer in the middle than at the base and apex, the latter being turgid, rather spherical, and armed with claws which probably lay hold of the skin while the animal is engaged in suction. When not used, the whole machine is withdrawn within the head; the siphuncle, which is the suctorious part, being first retracted within the tubulet, in the same way as a snail retracts its tentacula[1402]. This apparatus seems formed at the expense of all the other organs.

There are some other kinds of imperfect mouth, which, though they seem not to merit each a distinct denomination, should not be passed altogether without notice. The first I shall mention is that of the family of Pupipara Latr. (Hippobosca L.). It consists of a pair of hairy coriaceous valves, which include a very slender rigid tube or siphuncle, the instrument of suction, which Latreille describes as formed by the union of two setiform pieces[1403]. In Melophagus, the sheep-louse, the union of the valves of the sheath is so short, that they appear like a tube; but if cut off they will separate, and show the siphuncle, as fine as a hair, between them. This organ is of a type so dissimilar, as was before observed, to that of the Diptera in general, and approaches so near to that of the dog-tick (Ixodes), that they may be deemed rather apterous insects with two wings, than to belong to that Order; and the circumstance that some of the family are apterous confirms this idea. In fact they are a transition family that connects the two Orders, but are nearest to the Aptera. In Nycteribia the oral organs differ from those of the other Pupipara in having palpi. This also is the case with those of the genus Ixodes, the palpi of which are placed upon the same base with the instrument of suction, than which they are longer: they appear to consist of two joints, the last very long and flat. The instrument of suction itself is formed by three hard rigid laminæ; two shorter parallel ones above, that cover the third, which is longer and broader, and armed on each side with several teeth like a saw, having their points towards the base[1404]. Many of the other Acari L. have mandibles, and several have not: but their oral organs have not yet been sufficiently examined; and from the extreme minuteness of most of them, this is no easy task; nor to ascertain in what points they differ or agree.

If you consider the general plan of the organs of manducation in the vertebrate animals, how few are the variations that it admits! An upper and a lower jaw planted with teeth, or a beak consisting of an upper or a lower mandible with a central tongue, form its principal features. But in the little world of insects, how wonderful and infinite is the diversity which, as you see, in this respect they exhibit! Consider the number of the organs, the varying forms of each in the different tribes, adjusted for nice variations in their uses:--how gradual, too, the transition from one to another! how one set of instruments is adapted to prepare the food for deglutition by mastication; another merely to lacerate it, so that its juices can be expressed; a third to lap a fluid aliment; a fourth to imbibe it by suction--and you will see and acknowledge in all the hand of an almighty and all-bountiful CREATOR, and glorify his wisdom, power, and goodness, so conspicuously manifested in the structure of the meanest of his creatures. You will see also, that all things are created after a pre-conceived plan; in which there is a regular and measured transition from one form to another, not only with respect to beings themselves, but also to their organs--no new organ being produced without a gradual approach to it; so that scarcely any change takes place that is violent and unexpected, and for which the way is not prepared by intermediate gradations. And when you further consider, that every being, with its every organ, is exactly fitted for its functions; and that every being has an office assigned, upon the due execution of which the welfare, in certain respects, of this whole system depends, you will clearly perceive that this whole plan, intire in all its parts, must have been coeval with the Creation; and that all the species,--subject to those variations only that climate and different food produce,--have remained essentially the same, or they would not have answered the end for which they were made, from that time to this.

* * * * *

Having given you this particular account of the trophi or organs of the mouth of insects, I must now make some observations upon the other parts of the head. I have divided it, as you see in the Table, into face and subface; the former including its upper and the latter its lower surface. Strictly speaking, some parts of the face, as the temples and cheeks, are common to both surfaces; but I do not therefore reckon them as belonging to the subface, which, exclusive of the mouth and its organs, consists only of the throat, and where there is a neck, the gula.

i. Nasus[1405].--I shall consider the parts of the face in the order in which they stand in the Table, beginning with the nasus or nose. Fabricius has denominated this part the clypeus, in which he has been followed by most modern Entomologists. You may therefore think, perhaps, that I have here unnecessarily altered a term so generally adopted, and expect that I assign some sufficient reasons for such a change. I have before hinted that there is good ground for thinking that the sense of smell in insects resides somewhere in the vicinity of this part; and when I come to treat of their senses, I shall produce at large those arguments that have induced me to adopt this opinion: and if I can make out this satisfactorily, you will readily allow the propriety of the denomination. I shall here only state those secondary reasons for the term, which, in my idea, prove that it is much more to the purpose than clypeus. This last word was originally applied by Linné in a metaphorical sense to the ample covering of the head of the Scarabæidæ, and the thoracic shield of Silpha, Cassida, Lampyris, and Blatta: in all which cases there was a propriety in the figurative use of it, because of the resemblance of the parts so illustrated to a shield. But when Fabricius (though he sometimes employs the term, as Linné did, merely for illustration,) admitted it into his orismological table, as a term to represent universally the anterior part of the face of insects to which the labrum is attached (though in some cases he designates the labrum itself by this name), it became extremely inappropriate; since in every case, except that of the Scarabæidæ, the part has no pretension to be called a shield;--so that the term is rather calculated to mislead than illustrate. This impropriety seems at length to have struck M. Latreille, since in a late essay[1406] he has changed the name of this part to Epistomis, a term signifying the part above the mouth. But there are reasons, exclusive of those hereafter to be produced concerning the sense of smell, which seem to me to prove that nasus is a preferable term; not to mention its claim of priority, as having been used to signify this part a century ago[1407]. When we come to consider the terms for the other parts of the head, as lips, jaws, tongue, eyes, temples, cheeks, forehead, &c. the concinnity, if I may so speak, and harmony of our technical language, seem to require that the part analogous in point of situation to the nose of vertebrate animals should bear the same name. And any person who had never examined an insect before, if asked to point out the nose of the animal, would immediately cast his eye upon this part: so that one of the principal uses of imposing names upon parts--that they might be more readily known--would be attained. If it is objected, that calling a part a nose that has not the sense of smell, supposing it to be so, might lead to mistakes--I would answer, that this objection is not regarded as valid in other cases: for instance, the maxillæ are not generally used as jaws, and yet no one objects to the term; because, from their situation, they evidently have an analogy to the organs whose name they bear. But enough on this subject--we will now consider the part itself.

To enable you to distinguish the nose of insects when it is not separated from the rest of the face by an impressed line, you must observe that it is the terminal middle part that sometimes overhangs the upper-lip, and at others is nearly in the same line with it; that on each side of it are the cheeks, which run from the anterior half of the eyes to the base of the mandibles. Just below the antennæ is sometimes another part distinct from the nose, which I shall soon have to mention; so that the nose must not be regarded as reaching always nearly to the base or insertion of the antennæ, since it sometimes occupies only half the space between them and the upper-lip, which space is marked out by an impressed line. But you will not always be left at such uncertainty when you want to ascertain the limits of the nose; for it is in many cases a distinct piece, separated by an elevated or impressed line from the rest of the face. This separation is either partial or universal. Take any species of the genera Copris, Onitis, or Ateuchus, and you will see the nose marked out in the centre of the anterior part of the face by two elevated lines, forming nearly a triangle and bounded by the horn[1408]. Or take a common wasp or hornet, and you will find a similar space, though approaching to a quadrangular figure, marked out by impressed lines[1409]. In Rhagio and Sciara, two Dipterous genera, this impression is so deep as to look like a suture. Between these lines, in those cases, is included what I call the nose. As to substance, in general it does not differ from the rest of the head; but in the Cleridæ it is almost membranous. You must observe, that in all these, what at first sight appears to be the termination of the front, is not the nose, but the narrow depressed piece that intervenes between it and the lip. With regard to its clothing, it is most commonly naked, but in some genera it is covered with hair; in Crabro F. often with golden or silver pile, which imparts a singular brilliance to the mouth of the insects of that genus: M. Latreille supposes that the brilliant colours of the golden-wasp (Chrysis L.) may dazzle their enemies, and so promote their escape[1410]; the brilliance of the mouth of the Crabro may on the contrary at first dazzle their prey for a moment, so as to prevent their escape. The form of the nose, where distinct from the rest of the face, admits of several variations: thus in the Staphylinidæ and Cleridæ it is transverse and linear; in Copris it is triangular, with the vertex of the triangle truncated; in Vespa Crabro it is subquadrate and sinuated. In many Heteromerous beetles[1411] it is rounded posteriorly: in Pelecotoma, a new genus in this tribe, related to Asida, there is a deep anterior sinus; in Blaps the anterior margin is concave; in Cetonia[1412] Brownii, and atropunctata (forming a distinct subgenus), it is bifid: it varies in the Scarabæidæ, in some being bidentate, in others quadridentate, and in others again sexdentate, including the cheeks: in Mylabris, a kind of blister-beetle, it is transverse and nearly oval; in Lamia, a capricorn-beetle, it represents a parallelogram; and in most Orthoptera it is subtriangular: in Tettigonia F. it is prominent, transversely furrowed, and divided by a longitudinal channel: in Otiocerus K. it presents the longitudinal section of a cone[1413]: in the Diptera Order, with the exception of the Tipulidæ and some others, in which it unites with the cheeks, &c. to form a rostrum, the nose in general, as to form, answers to its name, resembling that of many of the Mammalia: in some of the Asilidæ it is very tumid at the end, and terminates in a sinus, to permit the passage of the proboscis to and fro: in many of the Syrphidæ, &c. it is first flat and depressed, and then is suddenly elevated, so as to give the animal's head the air of that of a monkey: in some tribes, as Rhingia, Nemotelus, Eristalis, &c., in conjunction with the cheeks it forms a conical rostrum: in Tabanus bovinus, and other horse-flies, it terminates in three angles or teeth. Many more forms might be mentioned, but these will suffice to give you a general idea of them. In size and proportions the nose also varies. It is frequently, as in Tettigonia, the most conspicuous part of the face, both for size and characters; but in the Staphylinidæ it is very small, and often scarcely discernible, being overshadowed by its ample front: and it may be observed in general, that when the antennæ approximate the mouth, as in this genus and many others, the front becomes ample, and the nose is reduced to its minimum: but when they are distant from the mouth, the reverse takes place; and the nose is at its maximum and the front at its minimum. Mutilla, Myrmecodes, Scolia, &c. in the Hymenoptera, are an example of the former; and the Pompilidæ, Sphecidæ, Vespidæ, &c. of the latter. In Myopa buccata, &c. its length exceeds its width; but more commonly the reverse takes place. The circumscription of the nose also deserves attention. It is usually terminated behind by the front (frons), or, where it exists, by the postnasus, in the sides by the cheeks, and anteriorly by the labrum. But this is not invariably the case; for in the Cimicidæ, in which the cheeks form the bed of the Promuscis, the front embraces it on each side by means of two lateral processes, that sometimes meet or lap over each other anteriorly, which gives the nose the appearance of being insulated; but it really dips below these lobes to join the labrum. This structure you may see in Edessa F., and many other bugs. This part sometimes has its arms. Thus in Copris, and many Dynastidæ, the horns of the head seem, in part at least, to belong to this portion of it; in Tipula oleracea (the crane-fly), &c. it terminates before in a horizontal mucro. In Osmia cornuta, a kind of wild-bee, each side of the nose is armed with a vertical horn. The margin of the nose in most Lamellicorn insects, though mostly level, curves upwards.

I am next to mention a part of the nose which merits a distinct name and notice, which I conceive in some sort to be analogous to the nostrils of quadrupeds, and which I have therefore named the Rhinarium or nostril-piece. I had originally distinguished it by the plural term nares, nostrils; but as it is usually a single piece, I thought it best to denote it by one in the singular. When I treat of the senses of insects, I shall give you my reasons, as I have before said, for considering this part as the organ of scent, or connected with it, which you will then be able to appreciate. I shall only here observe, that the piece in question is in the usual situation of the nostrils--between the nose and the lip. In a large number of insects this part may be regarded as nearly obsolete; or at least it is merely represented by the very narrow membranous line that intervenes between the nose and the lip and connects them; which, as in the case of the head of Harpali before noticed, may be capable of tension and relaxation, and so present a greater surface to the action of the atmosphere. But I offer this as mere conjecture. In the lady-bird (Coccinella) this line is a little wider, and becomes a distinct Rhinarium; as it does also in Geotrupes. With respect to its insertion, the rhinarium is a piece that either entirely separates the nose from the lip, or only partially: the former is the most common structure. It is particularly remarkable in a New Holland genus of chafers (Anoplognathus Leach). In A. viridiæncus it is very ample, and forms the under side of the recurved nose, so that a large space intervenes between the margin of the latter and the base of the labrum. In Macropus Thunb., of the Capricorn tribe (Cerambyx L.), the nostril-piece, which forms a distinct segment, is narrower than the nose, and the upper-lip than the nostril-piece, forming as it were a triple gradation from the front to the mouth. Again, in others the part in question is received into a sinus of the nose. This is the case with the dragon-flies (Libellulina), in which this sinus is very wide; in the burying-beetle (Necrophorus)[1414], in some species of which it is deep but narrow; and in a species of Tenebrio from New Holland, which perhaps would make a subgenus. If you examine with a common glass any of the larger rove-beetles (Staphylinidæ), you will find that the nose itself seems lost in the nostril-piece, both together forming a very narrow line across the head above the labrum, without any apparent distinction between them; but if you have recourse to a higher magnifier, you will find this divided into an upper and lower part, the former of the hard substance of the rest of the head, and the latter membranous. I once was of opinion that the prominent transversely furrowed part, so conspicuous in the face of Tettigonia F.[1415], was the front: but upon considering the situation of this, chiefly below the eyes and antennæ, and comparing it with the analogous piece in Fulgora laternaria and other insects of the Homopterous section of the Hemiptera, I incline to think that it represents the nose, and that the longitudinal ridge below it is the nostril-piece[1416]. In the Heteropterous section it is merely the vertical termination of their narrow nose. In other insects again, this part approaches in some measure to the common idea of nostrils; there being two, either one on each side the nose, or two approximated ones. If you catch the first humble-bee that you see busy upon a flower, you will discover a minute membranous protuberance under each angle of the nose. Something similar may be observed in some species of Asilus L. In the Orthoptera, especially in Blatta, Phasma, and some Locustæ, two roundish or square pieces, close to each other on the lower part of the nose, represent the nostrils[1417].--With regard to substance, in the chafer-tribes, at least those that feed on leaves or living vegetable matter, as the Melolonthidæ, Anoplognathidæ, and in many other insects, the rhinarium is of the same substance with the rest of the head; but in Macropus Thunb., Staphylinus, Necrophorus, &c., it consists of membrane.

ii. Postnasus[1418].--This is a part that appears to have been confounded by Entomologists with the front of insects; in general, indeed, it may be regarded as included in the nose, and does not require separate notice: but there are many cases in which it is distinctly marked out and set by itself, and in which it forms a useful diagnostic of genera or subgenera. There is a very splendid and beautiful Chinese beetle, to be seen in most collections of foreign insects (Sagra purpurea), in which this part forms a striking feature, and helps to distinguish the genus from its near neighbour Donacia. If you examine its face, you will discover a triangular piece, below the antennæ and above the nasus, separated from the latter and from the front by a deeply-impressed line: this is the postnasus or after-nose. Again: if you examine any specimens of a Hymenopterous genus called by Fabricius Prosopis (Hylæus Latr.), remarkable for its scent of baum, you will find a similar triangle marked out in a similar situation[1419]. In many Coleopterous insects, besides Sagra, you will discover traces of the part we are considering: as in Anthia, Dytiscus, and several others of the Predaceous beetles. In Cistela it is larger than the nose itself; but it is more conspicuous in the Orthoptera, particularly in Locusta (Gryllus F.), in which it is the space below the antennæ, distinguished by two or four rather diverging ridges[1420]. In the Libellulina, Myrmeleonina, &c. it is a distinct transverse piece. In Dasyga Latr., a kind of bee, it is armed with a transverse ridge or horn--But enough has been said to render you acquainted with it; I shall therefore proceed to the next piece.

iii. Frons[1421].--The Front of insects may be denominated the middle part of the face between the eyes, bounded anteriorly by the nose, or after-nose, where it exists, and the cheeks; laterally by the eyes; and posteriorly by the vertex. Speaking properly, it is the region of the antennæ; though when these organs are placed before the eyes, under the margin of the nose, as in many Lamellicorn and Heteromerous beetles, they seem to be rather nasal than frontal. This part is often elevated, as in the elastic beetles (Elater), whose faculty of jumping, by means of a pectoral spring, has been related to you[1422]. In Anthia, a Predaceous beetle, it has often three longitudinal ridges. In many of the Capricorn beetles (Cerambyx L.), it is nearly in the shape of a Calvary cross, with the arms forming an obtuse angle, and then terminating at the sinus of the eyes in an elevation for the site of the antennæ. In the ants also (Formicidæ), the front is often elevated between those organs. In Ponera, one tribe of them, this elevation is bilobed, and receives between its lobes the vertex of the postnasus. In the hornet (Vespa Crabro) the elevation is a triangle, with its vertex towards the mouth. In Sagra it is marked out into three triangles, the postnasus making a fourth, with the vertexes meeting in the centre. In the Dynastidæ and Scarabæidæ the horns are often frontal appendages, as is that of Empusa Latr., a leaf-insect, and probably those of Sphinx Iatrophæ F., which affords a singular instance of a horned Lepidopterous one. Sometimes it is an ample space, reducing the nose to a very narrow line, as in the Staphylinidæ, or sending forth a lobe on each side, as before mentioned, which embraces the nose. In a species of bug from Brazil, related to Aradus F., these lobes are dilated, foliaceous, and meet before the nose, so as to form a remarkable extended frontlet to the head. In others this part is extremely minute: thus in many male flies and other insects, as the Libellulina, where the eyes touch each other, the front is cut off from the vertex and reduced to a small angle. In the female flies the communication with the vertex is kept open, and the front consequently longer. In the horse-flies (Tabanidæ), in Hæmatopota, and Heptatoma, the frontal space is wider than in the rest of that tribe. Many of these are distinguished by a levigated area behind the antennæ in the part we are treating of. In the Libellulina, and in the drone-bee, whose eyes are confluent, the stemmata are in the front. In many Orthoptera also, as Locusta Leach, one of them is below the antennæ; and in the lanthorn-fly tribe (Fulgoridæ), both these organs, which are situate between them and the eyes, as they do also in Truxalis, appear to be in it[1423]. In this tribe the rostrum is an elongation of the part in question; and perhaps you would think at first that what I have considered as the nose in Tettigonia F. was also a tendency to this kind of rostrum; but if you examine the great lanthorn-fly (Fulgora laternaria), you will find besides, at the lower base of the lanthorn, a triangular piece analogous to the nose of Tettigonia, and below it another representing its nostril-piece:--the horizontal part of the nose in that genus may perhaps be regarded as part of the front. In Truxalis F. the face consists of a supine and prone surface, and the latter is composed of the front, after-nose, nose, and organs of the mouth. I may notice here a most remarkable and singular tribe of bugs, of which two species have been figured by Stoll[1424]: in these the head, or rather those parts of it that we have now been describing, the nose, namely, the after-nose, and front, are absolutely divided longitudinally in two, each half having an eye and antenna planted in it; or perhaps, as it is stated to be divided in one instance to the commencement of the promuscis, the nose is left intire, and dips down, as in cases before alluded to: so that in this the nose appears to leave the lobes of the front, which in others embrace its sides.

iv. Vertex[1425].--We now come to the vertex, or crown of the head; which is situated behind the front, and, except where the communication is intercepted by confluent eyes, adjoins it. It is laterally bounded by the hind part of the eyes and the temples; and posteriorly, where that part exists, by the occiput. The vertex may be denominated the ordinary region of the stemmata: for though in several cases, as we have just seen, one or more of them are planted in the front; yet this in the great majority, especially in the Hymenoptera, is their natural station. In Blatta and some other Orthoptera the posterior angle of the head is the vertex. In many dung-chafers of Latreille's genus Onthophagus, which are said to have occipital horns, as O. nutans, nuchicornis, Xiphias, &c., the horn really arms the part I regard as the vertex. In Locusta Leach, this part is very ample, and in Truxalis very long; but more generally it is small, and not requiring particular notice.

v. Occiput[1426].--The occiput, or hind-head, is that part of the face that either forms an angle with the vertex posteriorly, or slopes downwards from it. It has for its lateral boundaries the temples, and behind it is either terminated by the orifice of the head, or in many cases by the neck. In those beetles that have no neck, as the Lamellicorn and Capricorn, the hind-head is merely a declivity from the vertex, usually concealed by the shield of the thorax, very lubricous, to facilitate its motion in the cavity of that part, and at its posterior margin distinguished by one or two notches, which I shall notice hereafter, for the attachment of the levator muscles: but in those beetles or other insects that have a neck, or a versatile head, the occiput forms an angle with the vertex, often rounded, and sometimes acute. This structure may be seen in Latreille's Trachelides, and several other beetles. In the Hymenoptera, Diptera, and others with a versatile head, the part now under consideration curves inwards from the vertical line, so as with the temples and under parts of the head to form a concavity adapted to its movement upon the trunk.

vi. Genæ[1427].--The cheeks of insects (Genæ) usually surround the anterior part of the eyes, and lie between them and the mandibles or their representatives. Where they approach the latter, as in the Predaceous beetles (Cicindela, Carabus L. &c.), they are very short, and of course longer where the eyes are further removed from the mouth; as in the Rhyncophorous beetles (Curculio L.), where they form the sides of the rostrum, and often contain a channel which receives the first joint of the antennæ, when they are unemployed. In the Scarabæidæ and many other Lamellicorn beetles, their separation on each side from the nose is marked by a ridge[1428]; and in the wasps (Vespa) by an impressed line or channel. In an African tribe at present arranged with Cetonia F., to which C. bicornis Latr.[1429] and another, which he has named, I believe, C. vitticollis, belong, the cheeks are porrected on each side of the mouth into a horizontal horn. These horns have at first the aspect of a pair of open mandibles. In the magnificent Goliathi Lam., the horns of the male are rather a process of the cheek than of the nose. In Alurnus, Hispa, and other beetles, these parts, by their elevation and conjunction with the lower side of the head, form a kind of fence which surrounds and protects the oral organs; in many Cimicidæ, by a similar elevation of the cheeks, the bed of the promuscis is formed. In the Homopterous Hemiptera they run parallel nearly with the rhinarium or nostril-piece. In the Hymenoptera they are almost always ample, but they are confined to the lower side of the eye. In Sirex grandis, and others of that genus, the cheek at the base of the mandible is dilated so as to form a rounded tooth below it. In the Capricorn-beetles it is considerable, and sometimes terminates, at the base of the mandible, in two or three notches. In Scaurus and Eurychora, darkling-beetles, the cheek below projects into a lobe that covers the base of the maxilla. But the animal distinguished by the most remarkable cheeks is a species of Phryganea L. (Phryganea personata Spence); for from this part projects a spoon-shaped process, which curves upwards, and uniting with that of the other cheek, forms an ample mask before the face, the anterior and upper margin of which, in the insect's natural state, are closely united; and the posterior part being applied to the anterior part of the eye, causes the face to appear much swoln. It looks as if it was a single piece; but upon pressing the thorax it opens, both above and in front, into two parts, each convex without and hollow within, and each having attached to its inside a yellow tuft of hair resembling a feather. The use of this machinery at present remains a mystery[1430].

vii. Tempora[1431].--The temples (Tempora) are merely a continuation of the cheeks to the posterior limit of the head, forming its sides and posterior angles, and including the hinder part of the eyes, the vertex, and the occiput. They seldom exhibit any tangible character, except in certain ants (Atta Latr.), in which their angle terminates in one or two strong spines, giving the animal a most ferocious aspect; and in that remarkable genus Corydalis they are armed below with a tooth or point, which was not overlooked by De Geer[1432].

viii. Oculi[1433].--I must now call your attention to organs of more importance and interest, and which indeed include a world of wonders: I mean the eyes (Oculi) of insects. These differ widely from those of vertebrate animals, being incapable of motion. They may be regarded as of three descriptions--simple, conglomerate, and compound.

1. Simple Eyes[1434]. We will consider them as to their number, structure, shape, colour, magnitude, situation, and arrangement.

As to their number, they vary from two to sixteen. In the flea, the louse, the harvest-man (Phalangium), there are only a pair; in the bird-louse of the goose (Nirmus Anseris), and probably in others of the same genus, there are four[1435]; in some spiders (Scytodes, Dysdera, and Segestria Latr.[1436]), and some scorpions[1437], there are six. In the majority of spiders and Scolopendra morsitans, Scorpio maurus, &c. there are eight; and in Podura and Sminthurus Latr. there are sixteen[1438].

As to their structure, nothing seems to have been ascertained; probably their organization does not materially differ from that of one of the lenses of a compound eye; which I shall soon explain to you.

Their colour in the many is black and shining, but in the bird-louse of the goose they are quite white and transparent. In spiders they are often of a sapphirine colour, and clear as crystal. In Scolopendra morsitans and many spiders, scorpions, and phalangia[1439], they appear to consist of iris and pupil, which gives them a fierce glare, the centre of the eye being dark and the circumference paler. In the celebrated Tarantula (Lycosa Tarantula), the pupil is transparent, and red as a ruby; and the iris more opaque, paler, and nearly the colour of amber.

Where there are more than two, they vary in magnitude. In the enormous bird-spider (Mygale avicularia) the four external eyes are larger than the four internal[1440]; but in the Tarantula and Sphasus, the two or four internal are the largest. In Clubiona and Drassus they are all nearly of the same size[1441]; and in the Micrommata family they are very small[1442].

They vary also in shape. In Scolopendra morsitans the three anterior ones are round, and the posterior one transverse, and somewhat triangular. In Mygale calpeiana, a spider, the two smallest are round and the rest oval[1443]. In the trapdoor or mason spider (Mygale cæmentaria), the four small internal ones are round, and the large external ones oval[1444]; and those that are circumscribed posteriorly with an impressed semicircle, are shaped like the moon when gibbous[1445].

The situation and arrangement of simple eyes are also various. In many they are imbedded, as usual, in the head; but in the little scarlet mite, formerly noticed[1446], (Trombidium holosericeum), they stand upon a small foot-stalk[1447]: the hairiness of this animal might otherwise have impeded its sight. In spiders they are planted on the back of the part that represents the head, sometimes four on a central elevation or tubercle, and the remaining four below it--as in Lycosa; sometimes the whole eight are on a tubercle, as in Mygale; and sometimes, as in the common garden-spider (Epeira Diadema), upon three tubercles, four on the central one and two on each of the lateral ones. Other variations in this respect might be named in this tribe. In the scorpions a pair are placed one on each side, on a dorsal tubercle, and the other four or six on two lateral ones of the anterior part of the head[1448]. In the Phalangidæ the frontal eyes of the scorpion cease, and only a pair of dorsal ones are inserted vertically in the sides of a horn or tubercle, either bifid or simple, often itself standing upon an elevation which emerges from the back of the animal[1449]. If their eyes were not in a vertical and elevated position, the sight of these insects would be very limited; but by means of the structure just stated, they get a considerable range of surrounding objects, as well as of those above them. With regard to the arrangement of the eyes we are considering, it varies much. Sometimes they are placed nearly in the segment of a circle, as in those spiders that have six eyes only, before noticed[1450]; sometimes in two straight lines[1451]; at others in two segments of a circle[1452]; at others, in three lines[1453], and at others in four[1454]. Again, in some instances they form a cross, or two triangles[1455]; in others, two squares[1456]; in others, a smaller square included in a large one[1457]; in others, a posterior square and two anterior triangles[1458]; sometimes a square and two lines. Though generally separate from each other, in several cases two of the eyes touch[1459]; and in one instance three coalesce into a triangle[1460]. But it would be endless to mention all the variations, as to arrangement, in the eyes of spiders.

2. Conglomerate Eyes[1461] differ in nothing from simple eyes, except that instead of being dispersed they are collected into a body, so as at first sight to exhibit the appearance of a compound eye:--they are, however, not hexagonal, and are generally convex. They occur in Lepisma, the Iulidæ, and several of the Scolopendridæ. In Scolopendra forficata the eye consists of about twenty contiguous, circular, pellucid lenses, arranged in five lines, with another larger behind them, as a sentinel or scout, placed at some little distance from the main body. In the common millepede (Iulus terrestris) there are twenty-eight of these eyes, placed in seven rows, and forming a triangle, thus [Illustration: triangular eye shape]--the posterior row containing seven lenses, the next six, and so on, gradually losing one, till the last terminates in unity. Each of these lenses is umbilicated, or marked with a central depression. In Craspedosoma Leach, you will find a similar formation. In Glomeris zonata, a kind of wood-louse that rolls itself into a ball, the lenses are arranged in a line curved at the lower end, with a single one by itself at the posterior end on the outside; they are oblong and set transversely, and their white hue and transparency give them the appearance of so many minute gems, especially as contrasted with the black colour of the animal[1462]. Between these eyes and the antennæ is another transverse linear white body, but opaque, seemingly set in a socket, and surrounded by a white elevated line, like the bezel of a ring. Whether it is an eye, or what organ, I cannot conjecture[1463]. Its aspect is that of a spiracle.

3. Compound Eyes[1464].--These are the most common kind of eye in hexapod insects, when arrived at their perfect state; in their larva state, as we have seen, their eyes being usually simple[1465]; except, indeed, those whose metamorphosis is semicomplete, which have compound eyes in every state.--In considering compound eyes, I shall advert to their structure, number, situation, figure, clothing, colour, and size.

As to their structure,--when seen under the microscope they appear to consist usually of an infinite number of convex hexagonal pieces. If you examine with a good glass the eye of any fly, you will find it traversed by numberless parallel lines, with others equally numerous cutting them at right angles, so as apparently to form myriads of little squares, with each a lens of the above figure set in it. The same structure, though often not so easily seen, obtains in the eyes of Coleoptera and other insects. When the eye is separated and made clean, these hexagons are as clear as crystal. Reaumur fitted one eye to a lens, and could see through it well, but objects were greatly multiplied[1466]. In Coleopterous insects they are of a hard and horny substance; but in Diptera, &c. more soft and membranous. The number of lenses in an eye varies in different insects. Hooke computed those in the eye of a horse-fly to amount to nearly 7,000[1467]; Leeuwenhoeck found more than 12,000 in that of a dragon-fly[1468]; and 17,325 have been counted in that of a butterfly[1469]. But of all insects they seem to be most numerous in the beetles of Mr. W. S. MacLeay's genus Dynastes. In the eyes of these the lenses are so small as not to be easily discoverable even under a pocket microscope, except the eye has turned white[1470]: it is not, therefore, wonderful, that Fabricius should call these eyes simple[1471]. In some insects, however, as in the Strepsiptera Kirby, the lenses are not numerous: in Xenos they do not exceed fifty, and are distinctly visible to the naked eye[1472]. These lenses vary in magnitude, not only in different, but sometimes in the same eyes. This is the case in those of male horse-flies and flies, those of the upper part of the eye being much larger than those of the lower[1473]. The partitions that separate the lenses, or rather bezels, in which they are set, are very visible in the eyes just mentioned, and those of Xenos; but in many insects they are only discernible at the intersecting lines of separation between the lenses. In hairy eyes, such as those of the hive-bee, the hairs emerge from these septa. Every single lens of a compound eye may be considered as a cornea, or a crystalline humour, it being convex without and concave within, but thicker in the middle than at the margin: it is the only transparent part to be found in these most remarkable eyes. Immediately under the cornea is an opaque varnish, varying according to the species, which produces sometimes in one and the same eye spots or bands of different colours. These spots and bands form a distinguishing ornament of many of the Tabani and other flies. And to this varnish the lace-winged flies (Hemerobius, &c.) are indebted for the beautiful metallic hues that often adorn them. When insects are dead, this varnish frequently loses its colour, and the eye turns white: hence many species are described as having white eyes which when alive had black ones. The consistence of this covering is the same with that of the varnish of the choroid in the eyes of vertebrate animals; but it entirely covers the underside of the lens, without leaving any passage for the light. Below this varnish there are numbers of short white hexagonal prisms[1474], every one of which enters the concavity of one of the lenses of the cornea, and is only separated from it by the varnish just described: this may be considered as the retina of the lens to which it is attached; but at present it has not been clearly explained how the light can act upon a retina of this description through an opaque varnish. Below this multitude of threads (for such the bodies appear), perpendicular to the cornea, is a membrane which serves them all for a base, and which consequently is nearly parallel with that part. It is very thin, of a black colour, not produced by a varnish; and in it may be seen very fine white tracheæ, which send forth branches still finer, that penetrate between the prisms of the cornea: this membrane may be called the choroid. Behind this is a thin expansion of the optic nerve, which is a true nervous membrane, precisely similar to the retina of red-blooded animals. It appears that the white pyramidal threads which form the retina of each lens are sent forth by this general retina, and pierce the choroid by a number of almost imperceptible holes[1475]. From this description it appears that the eyes of insects have nothing corresponding with the uvea or humours of those of vertebrate animals, but are of a type peculiar to themselves.

Having explained to you the wonderful and complex structure with which it has pleased the CREATOR to distinguish the organs of vision of these minute beings, proving, what I have so often asserted, that when animals seem approaching to nonentity, where one would expect them to be most simple, we find them in many cases most complex, I shall now call your attention to the next thing I am to consider--the number of the eyes in question. Most insects have only two; but there are several exceptions to this rule. Those that have occasion to see both above and below the head, the eyes of all being immovable, must have them so placed as to enable them to do this. This end is accomplished in many beetles, for instance Scarabæus L., Helæus Latr., &c., by having these organs fixed in the side of the head, so that part looks upward and part downward; but in others four are given for this purpose. If you examine the common whirlwig (Gyrinus Natator) that I have so often mentioned[1476], which has occasion, at the same time, to observe objects in the air and in the water, you will find it is gifted with this number of eyes. Lamia Tornator (Cerambyx tetrophthalmus Forst.) and some others, of which I make a genus, under the appellation of Tetrops, are also so distinguished. In these insects, one eye is above and the other below the base of the antennæ; in fact, in these the canthus, instead of dividing the eye partially, as in the other Capricorn-beetles, runs quite through it at considerable width[1477]. In Ryssonotus MacLeay (Lucanus nebulosus K.) the eye appears also to be divided in two by the canthus. In the Neuroptera Order there is more than one instance of the same kind. In Ascalaphus there are two considerable eyes on each side of the head, which, though clearly distinct, meet like those of many male flies and the drone. The male, likewise, of more than one species of Ephemera, besides the common lateral eyes and the stemmata on the back of the head, have a pair of compound eyes on the top of a short columnar process[1478]. In the Hemiptera Order, also, an instance occurs of four eyes in the genus Aleyrodes[1479]. Amongst the vertebrate animals, there is an example of eyes with two pupils in Anableps, a genus of fishes[1480], but no vertebrate animal has four of these organs. That many insects should have more than two eyes, will not seem to you so extraordinary as that any should be found that, like the Cyclops of old, have only one. There is, however, an insect, before celebrated for its agility[1481] (Machilis polypoda Latr.), which has a single eye in its forehead; or we may say, its eyes are confluent, without any line of distinction between them except a small notch behind. Now that I am treating of the number of eyes, I must not forget to observe to you, that in some insects no eyes at all have been discovered. In Polydesmus complanatus, on each side of the head there is an eye-shaped portion separated by a suture, in which under a powerful lens I cannot satisfy myself that I can discern any thing like the facets that usually distinguish compound eyes. In Geophilus electricus, another myriapod, they certainly do not exist[1482]. Whence we may conclude, as was before observed[1483], that the faculty of emitting light is rather given it as a means of defence than to guide it in its path.

The situation of compound eyes differs in different tribes. In some, as in the Staphylinidæ, they are planted laterally in the anterior part of the head; in others, the Carabi &c., in the middle; in others again, Locusta Leach &c., in the posterior part. In some, their station is more in the upper surface, either before or behind; so that a very narrow space separates them, or perhaps none at all. Instances of this position of the eyes occur in a minute weevil (Ramphus Clairv.[1484]), and many Diptera, &c. Of those that form an union on the top of the head, some are placed obliquely, so as to leave a diverging space below them, as in many Libellulina[1485], the drone[1486], &c. Others, as Atractocerus, in which the eyes occupy nearly the whole head, and unite anteriorly, have this diverging space above their conflux. In Rhina barbirostris Latr., another kind of weevil, they are confluent below the head, at the base of the rostrum, and a very narrow interval separates them above. In a large number of the Heteromerous beetles, they are set transversely, in the Capricorn ones longitudinally. Their surface, when they are lateral, has usually two aspects, one prone to see below, the other supine to see above. In general the eyes are situated behind the antennæ, so that their position, whether it shall be anterior or posterior, depends upon that of those organs. Often, indeed, as in the last-named beetles, part of the eye is behind and part before the antennæ; but except where there are four eyes, as in Tetrops, they are never placed before or below them.

Though the eyes of insects are generally sessile, yet to give them a wider range they are sometimes, but it rarely occurs, placed, like those of many Crustacea, on a footstalk, but not a moveable one. An instance of this in certain male Ephemeræ has already been mentioned. In the Hemiptera De Geer has figured two species of bugs (Cimicidæ) that are so circumstanced[1487]; as are also all the known Strepsiptera K., though in these the footstalk is very short[1488]: but the most remarkable example of columnar eyes is afforded by that curious Dipterous genus Diopsis, in which both eyes and antennæ stand upon a pair of branches, vastly longer than the head, which diverge at a very obtuse angle from its posterior part[1489].

In their figure eyes vary much. Sometimes they are so prominent as to be nearly spherical: this is the case with some aquatic bugs, as Ranatra, Hydrometra, and several male Ephemeræ[1490]. Very often they are hemispherical, as in the tiger-beetles (Cicindela L.), and the clocks or dors (Carabus L.); but in a large number of insects they are flat, and do not rise above the surface of the head.--With regard to their outline, they are often perfectly round, as in many weevils; oval, as in various bees; ovate, as in other bees (Andrena F.); triangular, as in the water-boatman (Notonecta). They are also often oblong, and occasionally narrow and linear; as in that singular beetle Helæus. In many of the Muscidæ they form nearly a semicircle, or rather, perhaps, the quadrant of a sphere. The eyes of the Capricorn-beetles (Cerambyx L.) have a sinus on their inner side, as it were, taken out of them; so that they more than half surround the antennæ, before which is the longest portion of them. An approach to this shape is more or less observed in the darkling-beetles (Tenebrio L.); but in these the sinus is not so deep. I may under this head observe, that in those Mantidæ that represent dry leaves, and some others, these organs usually terminate in a spine[1491].

Though not distinguished by the beauty and animation that give such interest to the eye of vertebrate animals, and exhibiting no trace of iris or pupil, yet from the variety of their colours the compound eyes of insects, though most commonly black or brown, are often very striking. Look at those of one of the lace-winged flies that commit such havoc amongst the Aphides[1492], and it will dazzle you with the splendour of the purest gold, sometimes softened with a lovely green. The lenses of those of Xenos blaze like diamonds set in jet[1493]. You have often noticed the fiery eyes of many horse-flies (Tabanus L.) with vivid bands of purple and green[1494]. Others are spotted[1495]; and Schellenberg has figured one (Thereva hemiptera)[1496], that exhibits the figure of a flower painted in red on a black ground. These colours and markings are all most vivid and brilliant in the living insect, and often impart that fire and animation to the eyes for which those of the higher animals are remarkable. Take one of the large dragon-flies that you see hawking about the hedges in search of prey, examine its eyes under a lens, and you will be astonished at the brilliance and crystalline transparency which its large eyes exhibit, and by the remarkable vision of larger hexagons which appear in motion under the cornea, being reflected by the retina--all which give it the appearance of a living eye. This moving reflexion of the hexagonal lenses in living insects was noticed long since in some bees (Nomada F., Cœlioxys Latr.)[1497]

Compound eyes differ greatly in their size. In some insects, as Atractocerus, the drone-bee, many male Muscidæ, &c., they occupy nearly the whole of the head; while in others, as numerous Staphylinidæ, Locusta Leach, &c., they are so small as to be scarcely larger than some simple eyes of spiders: and they exhibit every intermediate difference of magnitude in different tribes, genera, and species.

Under this head I must say something of the Canthus of the eye; by which I mean an elevated process of the cheek, which in almost all the genera of the Lamellicorn beetles enters the eye more or less, dividing the upper portion from the lower. Though usually only a process of the cheek, yet in the Scarabæidæ the whole of that part forms the canthus[1498]. It only enters the eye in the Rutelidæ, Cetonidæ, &c.; it extends through half of it in Copris; it goes beyond the half in Ateuchus; and in Ryssonotus MacLeay (Lucanus nebulosus K.) it quite divides the eye into two[1499], as I before observed. In Lucanus, Passalus &c. it projects before the eye into an angle; in Lucanus femoralis nearly into a spine; but in Lamprima and Œsalus it does not exist. The part, also, that enters the eye in the Capricorn-beetles may be regarded as a kind of canthus, though it is merely a dilatation of the front.

4. Stemmata[1500].--Having given so full an account of the kinds and structure of the ordinary eyes of insects, you may perhaps expect that I should now dismiss the subject: you would, however, have great cause to blame me, did I not make you acquainted with a kind of auxiliary eyes with which a large portion of them are gifted; I mean those pellucid spots often to be found on the posterior part of the front of these animals, or upon the vertex, frequently arranged in a triangle. These, Linné, from his regarding them as a kind of coronet, called Stemmata. They have been of late denominated Ocelli; but as this latter term is also in general use for the eyelets on the wings of Lepidoptera, I have adhered to that of the illustrious Swede. Neither he nor Fabricius has expressed any opinion as to the use of these organs; but Swammerdam and Reaumur were aware that they were real eyes. The former found that there are nerves that diverge to them though not easily traced, and that they have a cornea, and what he takes for the uvea[1501]; and the latter has supposed that the compound eyes and these simple ones have, the one the power of magnifying objects much, and the other but little, so that the former are for surveying those that are distant, and the latter those that are near[1502]. The same author relates some experiments that he tried with the common hive bee, by which he ascertained that the stemmata, as well as the compound eyes, were organs of vision. He first smeared the latter over with paint, and the animals, instead of making for their hive, rose in the air till he lost sight of them. He next did the same with the former, and placing the bees whose stemmata he had painted within a few paces of their hive, they flew about on all sides among the neighbouring plants, but never far: he did not observe that these ever rose in the air like the others[1503]. From this experiment it seems as if the compound eyes were for horizontal sight, and the stemmata for vertical.

The definition of them by Linné and Fabricius as smooth, shining, elevated or hemispheric puncta, conveys a very inadequate idea of them; for, except in a very few instances, they are perfectly clear and transparent, and their appearance is precisely the same as that of the simple eyes of Arachnida &c., under which head they might very well have been arranged; but as the last are primary eyes, and the stemmata secondary, it seemed to me best that they should stand by themselves. The structure of both is probably the same, and their internal organization that of one of the lenses of a compound eye, and both are set in a socket of the head.

Though a large number of insects have them, they are by no means universal, since some Orders, as the Strepsiptera, Dermaptera, and Aptera, are altogether without them. The Coleoptera, also, have been supposed to afford no instance of species furnished with them; but in the last number of Germar and Zincken Sommer's Magasin, it is affirmed that they are discoverable in Gravenhorst's genus Omalium, but not in the kindred genera Micropeplus and Anthophagus[1504]. Upon examining the former genus, I find, that although Omalium planum and affinities, O. striatulum, and some others, appear not to have them, yet with the aid of a good magnifier they may be discovered in most species of that genus; as likewise in Evœsthetus Grav. I find them also very conspicuous in A. Caraboides and other Anthophagi, but some species appear to want them. In these insects they are two in number, situated in the vertex a little behind the eyes but within them, and either at each end of a transverse furrow, or at the posterior termination of two longitudinal ones. Nor are they found in all the genera of the other Orders. In the Orthoptera, the Blattidæ, unless a white smooth spot on the inner and upper side of the eyes may be regarded as representing them, have them not; but in all the other genera of that Order they are to be found[1505]. In the Hemiptera all the Cicadiadæ are gifted with them; as are likewise Tetyra, Pentatoma, with many other Cimicidæ, and the Reduviadæ very remarkably; but many others in both sections of this order, as Thrips, Coccus, Aphis, Capsus, Miris, Naucoris, Nepa, and Notonecta, &c. are deprived of them[1506]. Of the Neuroptera the Libellulina add stemmata to their large eyes, in the anterior angle of which they are stationed[1507]; but many other genera of that Order are without them; as Myrmeleon, Ascalaphus, Hemerobius, &c. The Trichoptera and Lepidoptera universally have them; though in the latter, except in Castnia and the Sphingidæ, they are not easily seen. In the Hymenoptera they are usually very conspicuous, but in Larra and Lyrops, two genera of this order, the posterior pair are scarcely discernible; and in the neuter ants they are quite obsolete. In the Diptera, though many genera are furnished with them, yet many also want them; amongst the rest Latreille's Tipulariæ, and all the horse-flies (Tabanus L.). The Pupiparæ (Hippobosca L.) usually have none; but in Ornithomyia avicularia, one of that tribe, though extremely minute they are visible, arranged in a triangle, in the polished space of their vertex.

As to the Number of the stemmata, three appears to be most universal. Reaumur mentions an instance in which he counted four in a fly with two threads at its tail; but great doubt rests upon this statement[1508]. Some Orthopterous genera, as Gryllotalpa, and many Hemipterous, as Tetyra, Pentatoma, Reduvius[1509], Cercopis, Fulgora[1510], &c., have no more than two; and in Larra and its affinities, as just observed, the posterior ones are obsolete, so as to leave only one discernible.

Where there are three of these organs, they are usually arranged in an obverse triangle in the space behind the antennæ, at a greater or less distance from them. In those male flies (Muscidæ) whose eyes are confluent, the stemmata are in a little area behind their conflux; but, as before observed, in the drone-bee and the Libellulina they are before it. This triangle is in some cases nearly equilateral, as in Perla related to the may-flies, and many Hymenoptera; in others it is acutangular, as in Locusta &c., in which the stemma forming the vertex of the triangle is before the antenna[1511]: in others, again, it is obtusangular, as you will see in Pepsis and various Hymenoptera. In the humble-bees (Bombus), a line drawn through them would form a slight curve. Their situation also varies. In insects that have only two, they are sometimes placed a little behind the eyes, or in the back part of the space between them: this is the case with most of the bugs (Cimex L.) that have them.--They are often distant, as in Tetyra F., Edessa F.; and sometimes approximated, as in Reduvius F.[1512] In many of the Homopterous Hemiptera, as Cercopis, Ledra, &c. they are planted in the upper part of the head[1513], but in Iassus their situation is on the under part; and in a North American subgenus, as yet without a name, they are exactly between the two, being placed in the frontal angle. In Fulgora their station is between the eyes and antennæ[1514]. They are most commonly sessile, and as it were set in the head; but in some, as Fulgora candelaria, they stand on a footstalk. The stemmata are set in the side of a frontal tubercle in that four-winged fly of threatening aspect, Corydalis, which in its perfect state has mandibles, but longer and more tremendous, like those that distinguish the larva only of the kindred genus Hemerobius[1515]. These organs differ little in shape, being usually perfectly round and somewhat convex; but occasionally they vary in this respect. In Fulgora serrata they are oblong, with a longitudinal depression; in F. Diadema they are also umbilicated, but the umbilicus is circular; in Corydalis they are oval; in other insects they are ovate; in some semicircular, and in a few triangular. They vary much in size: in some of these animals being so minute as to be scarcely visible, while in others, as Corydalis, Dorylus, Vespa pallida F., Reduvius, &c.[1515], they are as large as some compound eyes. They differ also in colour, though often black: in Fulgora laternaria they are of a beautiful yellow; in F. candelaria they are white; in many Hymenoptera they are crystalline, in others red: the fierce look of Reduvius personatus is rendered more hateful by its stemmata having a pale iris round a dark pupil[1516].

Let us here stop and adore the goodness of a beneficent CREATOR, who, though he has deprived these little beings of the moveable eyes with which he has gifted the higher animals, has made it up to them by the variety and complex structure of their organs of vision, where we have only two points of sight, giving them more than as many myriads.

5. Antennæ.--But of all the organs of insects, none appear to be of more importance to them than their Antennæ, and none certainly are more wonderful and more various in their structure, and probably uses. Upon this last particular I shall enlarge hereafter. Their structure, as far as it differs in the sexes, I fully discussed in a former letter[1517]; and the most remarkable kinds of them will be included in a set of definitions which I shall draw up for you before our correspondence on this part of my subject closes: I shall therefore now confine myself to the following particulars--namely, their number, insertion, substance, situation, proportion, general form and structure, clothing, expansion, motions, and station of repose.

As to their Number, in the majority of crustaceous animals the antennæ amount to four, but no insect has more than two. A genus recently established (Otiocerus Kirby[1518]) seems to afford an exception to this rule, since the species composing it at first sight appear to have four, and in some instances even six antennæ; but as only two of them terminate in a bristle, the other, though proceeding from the same bed of membrane, may perhaps be regarded as merely appendages. Germar, who has described a species of this genus[1519] under the name of Cobax Wintheri, considers these appendages as analogous to palpi: but as they do not proceed from the oral organs, but from the bed of the antennæ at the base of the nose[1520], they ought certainly to be regarded rather as accessories to the latter, than as representing the former. In the Aptera order the mites (Acacus L.) appear to be without these organs. In the pupiparous tribe Hippobosca they seem about to disappear; and in the Arachnida &c., as has been more than once observed[1521], the mandibulæ have been thought to represent, not indeed the antennæ of insects, but the inner pair of those of the Crustacea.

In considering the insertion of antennæ, by which I mean their articulation with the head, we must advert first to the orifice (Torulus) that receives them[1522]. This is a perforation of the crust of the head; commonly, though not invariably, circular: in Coleopterous insects often with concave lubricous sides, forming an acetabulum, with processes usual in ginglymous articulations, larger than the bulb or root of the antennæ; and which is commonly covered, except the central space occupied by the bulb, with a tense membrane. Though not in general remarkable, in some cases it merits attention. In the genus Rhipicera Latr., the elegant antennæ of whose males I have described in a former letter[1523], particularly the Brazilian species, it is a long process on each side of the nose, and might be mistaken for the first joint: in another Coleopterous genus, Priocera K.[1524], it has somewhat of the shape of a trumpet: in Cupes a tubercle rises just above the base of the antenna: a circular process forms the torulus in Fulgora and others. It is also often placed in a cavity of the front, as in several wild-bees, Melitta K., and in Locusta Leach on the sides of an elevation of that part[1525]. In a large majority of insects the bulb (Bulbus) or ball which is received by the bed, wears the appearance, especially in the Hymenoptera, of a distinct joint; but if you carefully examine it, you will clearly see that it is merely the base of the scape swelled out into a spherical or other kindred form[1526]; and often marked, as in the Cicindelidæ, with impressed points: as it is the piece by which the antenna moves in its socket, this form of a rotula was doubtless given for its more ready motion in all directions. This structure is principally conspicuous in the Coleoptera and Hymenoptera Orders: in the others the base is not so distinguished from the rest of the scape. If you carefully extract the antennæ of a beetle, say a Copris or Lamia, and examine its base or bottom, you will find that it is open for the transmission of muscles and nerves; that in its upper margin it has a deep notch or sinus, on each side of which is a smaller notch; and that all round the margin, which is very lubricous, a membranous ligament is attached, by which it was affixed in the torulus. Its articulation, therefore, seems of a mixed kind, like that of most other organs and parts of insects, partaking of the ligamentous, ginglymous, and ball and socket. In the Orthoptera, Hemiptera, &c. the articulation seems more purely ligamentous.

With regard to their substance--these organs are regulated, in some degree, by the nature of the integument of the animal of which they are appendages; in the softer insects being of a softer substance than they are in hard ones. The vertex of the joints, where they receive the succeeding one, appears in many cases to be softer than the rest of it, and especially towards the apex, often papillose. The antennæ are generally opaque; but in Nebria complanata, a beetle common on the sea-coast in Wales and Lincolnshire, they are semitransparent.

The situation of antennæ must next be considered. In this respect it seems necessary that they should be so situated as to be under the direction of the eyes: for if you examine ten thousand insects (except, as was before observed[1527], where there are four eyes), you will not find one in which these organs are situated either above or immediately behind them; their station being always either somewhere in the space between the eyes or that below them. In Ptinus F. they are placed near the vertex; but in Gibbium, which is so nearly related to that destructive genus[1528], they are beneath them. In many Melittæ K. they are in the middle of the space between the eyes; and in many other Hymenoptera and Coleoptera (Staphylinus &c.), in the anterior part of it. In many Lamellicorn genera (except in some Acridæ, as A. viridissima) as Melolontha, Cetonia, Lucanus, &c. they may be regarded as planted in the lower surface of the cheek before the eyes; but in Copris &c., in which they are inserted further under the shield of the head, they are properly in the prone surface of the front. In the Capricorn-beetles (Cerambyx L.) and Cnodalon F. they may be termed inocular, or placed in a sinus of the eye; in the former tribe in its interior, and in the latter its anterior side. In the Rhynchophorous or rostrum-bearing beetles (Curculio L.) they vary in their situation. Thus in Macrocephalus Oliv. they are inserted at its apex; in Anthribus in its middle, and in Calandra at its base[1529]. In the water-scorpions (Nepa, Belostoma, &c.) they may be called extraocular, being placed under the head in its prone part, outside the eyes[1530]. In Nirmus Fringillæ, a kind of bird-louse, they appear to be oral, being situated, according to De Geer, under the head near the mouth, at a great distance from the eyes[1531].

In their proportions, both as to length and thickness, antennæ vary extremely. Thus sometimes they are very short--much shorter than the head; as in the aquatic beetles Gyrinus, Parnus, and the water-scorpion; and some land-beetles, as Anthrenus, &c. At other times they far exceed the length of the insect: the males of many Capricorn-beetles are so distinguished. In that of Lamia ædilis they are more than four times as long as the body; and every intermediate length between these two may be found amongst them. They vary also greatly in thickness: in Paussus, whose antennæ emit light in the night[1532], and Cerapterus, they are nearly as thick,--at least their knob, which forms the chief part of them,--as the body of the insect[1533]; while in Mantis, Acrida K. and Psocus, they are as slender as a hair. The antennæ in many of the Prioni, especially in P. imbricornis, are thick from base to tip; while in other Capricorn-beetles they are quite the reverse.

It will not be necessary to enlarge here upon the general form of these organs: I shall therefore only notice the two principal divisions of them in this respect.--Antennæ, regard being had to one of their uses, may be divided into two sections, distinguished by forms extremely different: those, namely, that are employed by insects as tactors to explore their way, and those that cannot be so employed. The great majority are of the former kind; but those that may be denominated setigerous,--as the antennæ of the Libellulina, Ephemerina, of the Homopterous Hemiptera, and of many Diptera, the last joint of which terminates in a bristle, or is furnished with a lateral one, and of some gnats that have short feathered antennæ,--appear not fitted to be used as tactors to explore by touch, and form the latter description. This difference in these organs, as I shall have occasion to prove more at large hereafter, furnishes a strong presumption that their primary function is not touch. Were this the case, it would be common to them all.

As to their structure, antennæ consist in general of a number of tubular joints; each of which having separate motion, the animal is thereby enabled to give them every flexure necessary for its purposes. The scape, or first joint, by means of the bulb inosculates in the torulus, or is suspended to it; and the others, sometimes by a similar, though less pronounced knob at their base, inosculate in the preceding one; but in some cases the inosculation seems not so perfect, the joints being simply suspended by ligament. In pectinated or lamellated antennæ, the branch is usually a lateral process of the joint from which it issues; but in Phengodes (Lampyris plumosa L.) its involute plumose branches appear to articulate with the apex of each joint[1534]. I have a specimen of one of the Cleridæ, of a genus undescribed, in which each branch is forked. In some tribes of the Capricorn-beetles (Stenocorus, &c.) the antennæ are often armed at their apex with spines, sometimes on the upper side and sometimes below. In some aquatic beetles (Gyrinus, Parnus) they are furnished with an auricle at their base, which, like the lid of a box, shuts them in when unemployed, and protects them from the water[1535].

The portions into which antennæ may in general be considered as divided, have been sufficiently explained to you above; but it may not be amiss to add here a few words on the principal variations in their structure that I have had an opportunity of observing. The scapus[1536] or first joint, which includes the bulbus, is usually the most conspicuous joint in the antenna (exclusive, I mean, of the capitulum, in those in which that organ terminates in a knob), it being thicker and often longer than the succeeding ones. In the Capricorn and Darkling beetles, indeed (Cerambyx and Tenebrio L.), the third joint is the longest, but the scape is still the thickest; and in the stag-beetles (Lucanus L.), many of the weevil tribes (Curculio L.), and those of the bees (Apis L.), except in the males, it is as long nearly as the remainder of the antennæ, which forms an angle with it. In shape it is generally somewhat curved and subclavate, or increasing in size from the base to the summit; but it is sometimes straight and filiform, at others oblong or square, at others again triangular, in several instances three-sided: in one (Cetonia cruenta F. Genuchus K.) it is, as it were, broken, the upper part forming nearly a right angle with the lower; in Cerocoma Schæfferi it is foliaceous; and it is occasionally suborbicular: and probably many other forms might be enumerated.

The Pedicellus[1537] is the second, and may be deemed the least conspicuous joint of the antennæ. Though more slender than the scape, it is generally thicker than that which immediately follows it. In broken antennæ it is the hinge or pivot on which the clavola or upper member turns: it is usually very short, campanulate or bell-shaped, or obconical; but in a species of bug (Tetyra, from New Holland--T. pedicellata Kirb. MS.) it is nearly as long as all the rest of the joints taken together. In those species of Lycus, a genus of beetles related to the glow-worm, that have flattened antennæ (as L. reticulatus, fasciatus, &c.), this joint is almost received into the socket of the scape, so that their antennæ appear at first to have only ten joints, but in those which have those organs filiform (as L. minutus, Aurora, &c.) it is more conspicuous.

The Clavola[1538], or remaining joints of the antennæ taken together, constitutes the principal part of the organ, which, especially at its extremity, exercises its functions of touch, or any other sense. The principal variations, as to form and structure, that occur in this part will be mentioned in another place. I shall only here observe, that in many instances the first joint of this part is longer than the rest; but in Tetyra pedicellata just mentioned, it is by far the shortest, and shaped like the pedicel of most insects. In the Libellulina, the Homopterous Hemiptera, and those flies whose antennæ terminate in a bristle, the clavolet is represented by the bristle. But in the flies which have a lateral bristle, on the last joint, and those with triarticulate antennæ that have no bristle, the terminal joint represents it. The clavolet often terminates in a knob, or in several joints thicker than that which precedes them. This varies greatly, not only in its form, but also in the number of joints of which it is composed. Thus in Paussus, Platypus, and many Calandræ, it consists of only a single joint[1539]; in Anthrenus, Ditoma, &c. of two; in Nitidula, Geotrupes, &c. of three[1540]; in Tetratoma, the Silphidæ, of four[1541]; of five in Scaphidium[1542]; of six in one species of Languria, of seven in the common cockchafer (Melolontha vulgaris[1543]); of eight in Diaperis Boleti, in which the whole clavolet forms the club[1544]; of nine in Oenas; and ten in Cerapterus[1545]. All the above, you will observe, are beetles. In the other orders there are eleven joints in the knob of some butterflies; twelve in that of Ascalaphus[1546] and Myrmeleon; and lastly, fourteen in Trachelus[1547].

Under structure also, the number of joints of which antennæ in general consist, should be considered. If you examine the insects belonging to the different orders, you will find remarkable variations in this respect. Let us run through them:--In the Coleoptera the natural number of joints is eleven; but this rule is not without many exceptions. Thus, many have fewer than the prescribed number: Paussus has only two[1548], Claviger and Platypus five, Dorcatoma and Calandra eight[1549], Geniates K. and Phanæus MacLeay nine[1550], and lastly Melolontha ten[1551]. Others, again, have more than eleven joints: Cebrio grandis, Chrysomela stolida, some Saperdæ, and several others, have twelve. In Prionus imbricornis the female has nineteen, and the male twenty[1552]. Rhipicera marginata has thirty-two; and in a New Holland species of this genus I counted thirty-eight. In the Orthoptera I can trace no general law in this respect. In Locusta Leach in some species you may count fourteen joints, in others sixteen, and in others twenty-five. In one, which appears to be a pupa, I found only thirteen. In Mantis they exceed thirty; but in Blatta, from between thirty and forty, they reach nearly one hundred and fifty; often varying in number in different individuals of the same species. The order Hemiptera exhibits two peculiar types of antennæ, which, with some exceptions, distinguish the two natural sections into which M. Latreille has judiciously divided it. In the Heteropterous section they are without a bristle at their end; and in the Homopterous one, with the exception of Aphis, Thrips, &c. they have one. In the genera of both these tribes, the number of joints varies in these organs. Thus, exclusive of the seta, in Flata and Cixius there are only two joints; in Galgulus, Fulgora, and Cercopis, there are three; in Lygæus, Coreus, &c. there are four; in Tetyra, Pentatoma, Tettigonia, there are five[1554]; in Aleyrodes there are six; in Aphis seven; in Thrips eight; in Psylla ten, the last of which is terminated by two bristles[1555]; and in Coccus eleven. The Neuroptera order, as it stands at present, is regulated by no general rule with regard to the number of joints in the antennæ of the insects that compose it. Several types of form in these organs distinguish its discordant tribes. The first is that of the Ephemeræ, in which the antennæ consist of two short joints, crowned by a short, tapering, unjointed bristle. The second is that of the Libellulina, similar to the above, but with a jointed bristle. The third is that of Psocus, in which the antenna has two short thick joints at the base, terminated by a long filiform bristle, consisting of seven or eight joints, and finer than a hair. Perhaps these three may be regarded as belonging to a common type. The fourth type is presented by the short filiform antennæ of Termes; the fifth by the setaceous ones of Corydalis, Hemerobius, &c.; and the sixth and last by the clavate and capitate ones of Myrmeleon and Ascalaphus. In the Lepidoptera and Trichoptera orders the antennæ, though varying in their general form in the three tribes of which Linné formed his genera Papilio, Sphinx, and Phalæna, with the exception of Hepialus, in which the joints are few, are always multiarticulate:--we will therefore, without further delay, proceed to the Hymenoptera. In Latreille's tribe Aculeata the general rule is, that the females shall have twelve joints and the males thirteen. In his Ichneumonides the law seems to be, that the antennæ shall be multiarticulate and setaceous; but in most of the other tribes of the order, even those that in other respects are most nearly related,--as in his Tenthredinetæ,--the number of joints of these organs varies without end. Thus in Hylotoma there are only three joints[1556]; in Cimbex læta[1557] five; in C. axillaris and Perga Leach[1558], six: and so on to twenty-five or more[1559]. The same fluctuation in this respect runs throughout the rest of the order. In the Diptera there are two general types of antennæ:--those of the Tipulariæ Latr., consisting usually of from fourteen to sixteen joints, in the males often resembling beautiful plumes; and those of the remainder of the order, in which they do not exceed three joints[1560]: though the last, or patella, is often further divided into obsolete or indistinct ones[1561]. These antennæ may be further subdivided into filatæ and aristatæ, or those without and those with a bristle, either lateral or terminal.

The clothing of antennæ also merits attention, since it is often not a little remarkable. By clothing I understand the down or hairs of every kind with which they are either generally or partially covered. A great number of filiform and setaceous antennæ of Predaceous beetles (Cicindela L., Carabus L.) have the first two, three, or four joints naked, and the rest covered with a fine down. In insects that have a knob at the end of these organs, whether lamellated or perfoliate, this down is often confined to it, or to its intermediate joints, and seems intermixed with nervous papillæ. These are particularly visible in the flabellate antennæ of Rhipicera, Lampyris Latreillii[1562], Elater flabellicornis[1563], &c. covering both surfaces of the processes of the joints. In some male bees these papillæ are inclosed in hexagonal spaces into which the antennæ are marked out[1564]. It is to be observed, that in many antennæ the joints of the clavolet have one or two bristles or more at their apex, one above perhaps, and one below; the lower angle in those of the serrated antennæ of Elater is usually so furnished, and sometimes the upper. In many Capricorn-beetles and various insects the antennæ are clothed, instead of down, with stiffish hairs or short bristles. Other insects have these organs, at least the clavolet, beset with longer hairs standing out from them on all sides: of this kind are those of a singular beetle (Sarrotrium muticum) sometimes found in this country[1565]. Again, there are some that have only their underside bearded with longer hairs; as Lamia curculionoides, speculifera K., and other Capricorns[1566]. In another of this tribe, Saperda hirsuticornis, the three intermediate joints are ornamented with branches of long black hairs, which give them an elegant and feathery appearance[1567]. In Callichroma alpina the apex of the slate-coloured joints of its antennæ is bearded with black hairs. In Lamia reticulata, and Saperda fasciculata and plumigera, all also Capricorns, a single bunch of hairs, resembling the brush of a bottle-cleaner, signalizes the middle of the antenna[1568]: in Saperda scopulicornis K. this is star-shaped[1569]. Sometimes the scape is externally bearded, as in Trox, a beetle found in horns and bones; and in many other Lamellicorns[1570]. In this last tribe the two exterior leaves of the knob of the antennæ are often set with short bristles[1571]; and in a minute beetle called by De Geer Dermestes atomarius, the hairs of this part are said to form a brush[1572].

When insects, I mean more particularly Coleoptera, are about to move from any station where they have been at rest, the first thing they usually do, before they set a step, is to bring forward and expand their antennæ, which have either been carefully laid up in a cavity fitted to receive them, or back upon the body: if they terminate in a lamellated knob, they separate the lamellæ as far as possible from each other; or if it is perfoliate, the joints of it mutually recede. The object of this is evidently to collect notices from the atmosphere, since the papillose part of these joints cannot be applied to surfaces. When the animal begins to move, in many cases the antennæ do the same, and continue their motion till it stops and returns to a state of repose. In the parasitic tribes of the Hymenoptera (Ichneumon L.) they are kept in an almost constant vibration. Many other insects move them in all directions without any order or regularity; and others, when they elevate one depress the other, and so proceed as if balancing themselves by means of these organs like a rope-dancer. I have before stated to you how by motions of their antennæ, ants and bees communicate their wants or discoveries to each other, or make inquiry concerning any thing they wish to know[1573]. But as I shall have occasion to make some further remarks upon this subject, when the senses of insects are under discussion, I shall for the present take my leave of it.

I shall conclude what I have to communicate to you relative to the organs of which we are treating, with a few observations with respect to their station when the insect reposes. In the Capricorn-beetles, Eucera and other insects with long antennæ, they are merely turned back or on one side with no particular cavity for their reception when unemployed, but probably the apex passes under the body. In the Predaceous and Darkling beetles (Carabus L., Tenebrio L.) their station is usually under the sides of the prothorax, and in the Tortoise beetles (Cassida), under its anterior margin. In the Elastic beetles (Elater) they are received into a groove between the under margin of that part and the fore-breast (antepectus). In Anthrenus, when the animal reposes or counterfeits death, the antennæ are concealed in a cavity of the underside of the prothorax, at right angles with the throat[1574]. In the kindred genus Byrrhus, another simulator of death, a large cavity is excavated under the same part, to receive both the forelegs and antennæ, a narrow space being left between the angle of the prothorax and fore-breast exactly admitting the base of the latter, which are quite concealed under the former. In Cryptocephalus and Chlamys, kindred beetles, when at rest they are withdrawn, except their scape and pedicel, with the head within the cavity of the prothorax. In others they are turned under the head, without any particular cavity for their reception; as in many moths, Apion, &c. In most of the Lamellicorn beetles their station is in the cavity formed by the eye and the throat, the knob forming an angle with the rest of the antenna. In Heterocerus they follow the contour of the eye[1575]. In Brentus, a genus of weevils remarkably long and slender, they are turned back and received by a slight longitudinal cavity of the rostrum; but in those of this tribe (Curculio L.) in which the clavolet forms an angle with the long scape, this latter part, bending back, is laid up in an oblique channel of that part; and the former, pointing in the contrary direction, is folded upon it. In many flies (Muscidæ) a vertical frontal cavity receives the antennæ, which point downwards during repose[1576]. Cryptocerus, a very remarkable ant, has on its head a singular square plate, the sides of which form a deep longitudinal cavity: in this cavity the antennæ, quite concealed, repose in safety. A cavity equally remarkable is exhibited by the water-scorpions, particularly Belostoma, in which is a very deep kidney-shaped box, between the eye and throat, to receive and defend its singular antennæ[1577]; which, when they are reposing, is closed by the exterior harder joints, and from which it seems as if they turned out, like a sentinel out of his box. In some aquatic genera of beetles, as Gyrinus, Parnus, &c. they are withdrawn within a lateral cavity of the same part, and are defended from the water externally by the auricle at their base[1578]. The flabellated and lamellated antennæ, previous to their being folded for repose, close all their plates; which in action are as widely expanded as possible, so as to form a knob; and in some the middle piece is entirely concealed, as if in a box. In broken antennæ, or those in which the clavolet forms an angle with the scape, the former is folded upon the latter, with its point downwards.

II. Subfacies.--Having dispatched the Facies, or upper side of the head, I am next to consider the Subfacies, or under side: but as the principal parts that occupy this side have been already considered, I shall have no occasion to detain you long.

i. Jugulum[1579].--This part, which may be regarded as analogous to the throat in vertebrate animals, lies between the cheeks; from which it may usually be distinguished by being more lubricous and tumid, and often separated by an impressed line. It is particularly conspicuous and elevated in the Lamellicorn beetles, and calculated by its lubricity for easy motion in the lower side of the cavity of the chest. Its apex is the base in which the mentum sits. It is not necessary to enlarge further upon it, as it seldom exhibits striking characters.

III. Collum[1580].--In a large proportion of insects the head inosculates in the trunk without the intervention of a neck, or a constriction of the head behind. In the Orders Orthoptera, Trichoptera, Lepidoptera, Hymenoptera, and Diptera, no instance of it that I recollect occurs: in the Coleoptera there are many. In the Predaceous beetles, though several have no distinct neck, yet others, as Anthia, &c. have a short and thick one; and some few, as Colliuris, Agra, &c. one more pronounced. Latreille has named a tribe in this Order Trachelides, from the circumstance of their having a neck: in this tribe you will find the blister-beetles (Cantharis and Mylabris) both of the moderns and the ancients. In the Hemiptera order the water-scorpions Nepa, &c. have a thick short neck; and Zelus, (a kind of bug,) one longer and more slender; and, like Raphidia, the snake's-head fly, which is similarly circumstanced, has the air of a serpent. Other Neuroptera, likewise, have a neck; as Hemerobius, Corydalis, &c. This part presents no other features that merit notice.

IV. Myoglyphides[1581].--The Myoglyphides, or muscle-notches, are sinuses, some shallow and some deeper, in the posterior margin of the upper side of the head, to which the levator muscles are affixed. They seem principally confined to the Coleoptera; though, in some cases at least, they may be traced in the Heteropterous Hemiptera. These notches vary in number and depth in different insects. Thus in Buprestis there is only one deep one[1582]: in Copris there are two shallow ones, in a deep sinus separated by a small prominence[1583]: in Elater and Lamia there are also two not in a sinus; and in Calandra Palmarum there are four, two on each side, with a prominent lobe between them[1584]. To each of these notches, at its under margin, below the ligament that unites the occiput to the trunk, a muscle to raise the head is usually attached.

FOOTNOTES:

[1151] See above, p. 86, 110, 243--.

[1152] Many species of Hister, Curculio L., Doryphora Illig. are extremely hard, while Cantharis Geoffr., Meloe F., and Telephorus Geoffr., are very soft.

[1153] Thenard Traité de Chimie Elémentaire, iii. 637. n. 2005. The other products he mentions are--a green oil, a yellow substance, a black ditto, acetic acid, uric acid, phosphate of magnesia. The vesicant matter consists of little micaceous laminæ soluble in boiling alcohol and oil, but insoluble in water.

[1154] Coquebert Illustr. Icon. ii. t. xviii. f. 14, 15.

[1155] Linn. Trans. xii. t. xxii. f. 16.

[1156] This name I would give to Locusta F., reserving, with Dr. Leach, the latter name to the true locust (Gryllus F.). The name Conocephalus, by which Locusta F. has been distinguished, is better restricted to those with a conical head.

[1157] PLATE XXVIII. FIG. 1, 2.

[1158] Huber Nouv. Obs. ii. 317.

[1159] VOL. I. p. 502--.

[1160] Hair, in the Holy Scriptures, is used as the symbol of strength or power. Judges xvi. 17--. 1 Cor. xi. 10.

[1161] Anat. Compar. ii. 624.

[1162] Anat. Compar. i. 119.

[1163] Ibid. ii. 540.

[1164] Ibid. 547.

[1165] Ibid. 553.

[1166] Anat. Compar. ii. 553.

[1167] Ibid. 557.

[1168] Ibid. 560.

[1169] PLATE XXVIII. FIG. 2. a´´´.

[1170] Anat. Compar. ii. 557.

[1171] A harmonic suture is when the margins of two flat bones simply touch each other, without any intermediate substance; and a squamose, when the thin margin of one covers that of the other. Anat. Compar. i. 124. With regard to the flat portions of the integument of insects, they have some motion; whereas a suture is an articulation without movement. Ibid.

[1172] Their connexion by means of a ligament classes them under Synneurosis (Monro On the Bones, Dr. Kirby's edit. 29), but even this not strictly, since a common ligament connects them all. Those of the trunk, as admitting a slight degree of motion, belong to Amphiarthrosis (Anat. Compar. i. 126), and those of the abdomen, which are capable of larger movements, to Diarthrosis (Ibid. 127).

[1173] See above, p. 309--.

[1174] In the hornet and other wasps, this line on the inside of the head furnishes a foundation for a septum, which in the sides of the nose is very high, and connects also with the hind part of the head.

[1175] Anat. Compar. i. 445--.

[1176] Ibid. 447.

[1177] Mém. sur les Anim. sans Vertèbr. I. i, 11--. Comp. Anat. Compar. iii. 314--.

[1178] It is probable that M. Cuvier took his idea of this first kind of articulation, by contact of solid parts, from this individual insect; since, besides its very prominent throat, there is on each side of the lower part of the occiput a small elevation, or approach to a tubercle.

[1179] Gen. des Crustac. et Ins. ii. 246. Regne Anim. iii. 325.

[1180] This was written directly after the experiment recommended in the text had been tried, with the result there stated.

[1181] Reaum. iv. 40. Latreille Fourmis, 328--.

[1182] PLATE VII. FIG. 2. k´´.

[1183] Clairville (Ent. Helvet. i. 44) appears to have been the first who classed insects according to their mode of taking their food.

[1184] PLATE VI. VII. XXVI. a´.

[1185] In Lucanus, Lamprina, &c. the labrum seems to form the under-side of the nose, and to be connate with it.

[1186] Kirby Mon. Ap. Angl. i. t. v. Apis *. b. f. 18. b.

[1187] Ibid. t. ii. Melitta **. b. f. 4, 5. PLATE XXVI. FIG. 30.

[1188] PLATE XXVI. FIG. 31. Mon. Ap. Angl. i. t. x. Apis **. c. 2. δ. f. 13. c.

[1189] PLATES VI. VII. and XXVI. b.

[1190] De Geer iv. 124. t. iv. f. 12. iii. 415. t. xxi. f. 4.

[1191] Ibid. iv. 281--. t. xi. f. 7.

[1192] Ibid. 329. t. xii. f. 3.

[1193] Ibid. ii. 775--. t. xxvi. f. 10. b c, b c.

[1194] Philos. Entom. 18.

[1195] Syst. Eleuth. i. Præf. iv.

[1196] Gen. Crustac. et Ins. i. 180.

[1197] N. Dict. d'Hist. Nat. iv. 246.

[1198] PLATE VI. FIG. 6. b´. a´´.

[1199] PLATE VII. FIG. 3. b´. a´´.

[1200] Kirby Linn. Trans. xii. t. xxi. f. 8. f.

[1201] Ibid. t. xxi. f. 10. d. MacLeay Hor. Entomol. i. t. iii. f. 26, 27.

[1202] PLATE XXVI. FIG. 35.

[1203] Ibid. FIG. 34.

[1204] PLATE VII. FIG. 3. b´.

[1205] PLATE XXVI. FIG. 24. b´.

[1206] PLATE VII. FIG. 3. a´´.

[1207] N. Dict. d'Hist. Nat. xxiv. 171.

[1208] PLATE VI. FIG. 6. e´.

[1209] PLATE VII. FIG. 3. i´´.

[1210] PLATE VI. FIG. 12. e´.

[1211] PLATE VI. FIG. 6. b´.

[1212] Ibid. FIG. 12. b´.

[1213] PLATES VI. VII. XXVI. b´´.

[1214] PLATE VI. FIG. 6. b´´.

[1215] Hor. Entomolog. i. t. i. f. 1. g.

[1216] Ibid. t. ii. f. 18. g.

[1217] Kirby Mon. Ap. Angl. i. t. xii. neut. f. 1. g. c.

[1218] Ibid. 93. 103--. t. vi. Apis **. b. f. 3. b. c.

[1219] Ibid. t. i. *. a. f. 3. b.

[1220] Ibid. t. ix. Apis **. c. 2. γ. f. 3. b.

[1221] Clairv. Ent. Helvet. ii. t. xxiv. f. 1. c.

[1222] PLATE XXVI. FIG. 24, 28. b´´.

[1223] Mon. Ap. Angl. i. t. ii. Melitta **. b. f. 2. c.

[1224] PLATE XIII. FIG. 2. Linn. Trans. xii. t. xxi. f. 6. b.

[1225] This is the case with Oxyporus F. PLATE XIII. FIG. 4.

[1226] PLATE VI. FIG. 12. b´´. Latreille, N. Dict. d'Hist. Nat. xvii. 545, seems not to regard these as palpi; but from their tubular form, and insertion in the socket of the labium, it is clear that they ought to be so considered.

[1227] PLATES VI. VII. XXVI. c´.

[1228] A corresponding articulation takes place between the tibia and thigh of some of the Scarabæidæ, which will be hereafter described. See PLATE XXVII. FIG. 8-11.

[1229] Comparaison des Organes de la Mastication des Orthoptères, 2.

[1230] Comparaison des Organes de la Mastication des Orthoptères, 2.

[1231] See above, p. 407. note b.

[1232] Ubi supra, 4.

[1233] Ibid.

[1234] Ibid. 5.

[1235] Oliv. Ins. no. 66. Prionus. t. xiii. f. 54.

[1236] Ibid. no. 83. Curculio. t. iv. f. 37.

[1237] Linn. Trans. xii. t. xxi. f. 12.

[1238] For Mandibles of Locusta see PLATE VI. FIG. 6. c´. of Lampyris Oliv. Ins. no. 28. t. i. f. 1. of Buprestis, Ibid. no. 32. t. iii. f. 17. of Lucanus, Ibid. no. 1. t. i-v. and of Prionus, Ibid. no. 66. t. ii. f. 8.

[1239] Gomphosis is, when one bone is immoveably fixed in another as a nail in a board.

[1240] Marcel de Serres ubi supra. 7.

[1241] See PLATE XIII. FIG. 7. Kirby Mon. Ap. Angl. i. t. xiii. f. 13. and t. xii. neut. f. 10.

[1242] PLATE XXVI. FIG. 19.

[1243] Oliv. Ins. no. 42. t. i. f. 1. and no. 2. t. i. f. 1. b.

[1244] PLATE XXVI. FIG. 16, 18.

[1245] Ibid. FIG. 21.

[1246] Mon. Ap. Angl. i. t. iv. Melitta. f. 5-8.

[1247] Drury Ins. ii. t. xlviii. f. 3. See above, p. 315.

[1248] Oliv. no. 1. t. v. f. 16. &c. t. iii. f. 7.

[1249] Comparaison des Organes, &c. 7--.

[1250] PLATE VI. FIG. 6. and XIII. FIG. 5. a´´´.

[1251] PLATE VI. FIG. 12. and XIII. FIG. 5. b´´´.

[1252] PLATE XXVI. FIG. 16.

[1253] I was not aware that Knoch had observed this part, till some time after the publication of my paper On Mr. William MacLeay's Doctrine of Affinity and Analogy (see Linn. Trans. xiv. 105--), when I happened to meet with it in a letter from a friend, received more than thirteen years ago; but without any reference to the work of Knoch, in which it was stated. It was doubtless taken from his Beiträge zur Insektengeschichte.

[1254] Anat. Comp. iii. 321--.

[1255] One of those mandibles is represented in PLATE XXVI. FIG. 20. a´´´. incisive teeth d´´´. molary plate. Comp. Linn. Trans. ubi supr. t. iii. f. 4. c a b.

[1256] VOL. II. p. 275--.

[1257] In the Myrmeleon, or ant-lion, the suction is promoted by the action of a piston, that pumps up the juices. Reaum. vi. 369.

[1258] De Geer iv. 386--. t. xv. f. 10. See above, p. 121.

[1259] PLATE XIII. FIG. 7. c´´.

[1260] Oliv. Ins. no. 42. Staphylinus. t. i. f. 1. b.

[1261] PLATES VI. VII. XXVI. d´.

[1262] PLATE VI. FIG. 3, 6, 12. VII. FIG. 3. c´´.

[1263] PLATE VII. FIG. 3. a´´. e´´. Mon. Ap. Angl. i. t. xiii. f. 1. e.

[1264] Ibid. f. 3. a.

[1265] Clairv. Ent. Helvet. ii. 146. t. xxiii. f. super. b.

[1266] N. Dict. d'Hist. Nat. iv. 243.

[1267] In Anoplognathus, however, though it has neither teeth nor spines, it is as hard as the mandibles.

[1268] See above, p. 317.

[1269] PLATE XXVI. FIG. 10, 11. d´´´. e´´´.

[1270] Ibid. FIG. 9. d´´´. e´´´.

[1271] PLATE VI. FIG. 6, 12. d´´´. e´´´. Oliv. Ins. no. 45. Meloe. t. i. f. 1. c. These are what Fabricius calls galeate maxillæ, on which he founded his class Ulonata.

[1272] PLATE XXVI. FIG. 11. d´´´. e´´´.

[1273] PLATE VI. FIG. 3. d´´´.

[1274] Clairv. Ent. Helvet. t. i. t. xviii. f. super. b.

[1275] Ibid. t. xix. b. This genus may be the analogue of some heteromerous one yet undiscovered, as Calosoma is of Adelium (Kirby Linn. Trans. xii. t. xxii. f. 2.)

[1276] Clairv. Ent. Helvet. ii. t. xxiv. f. super. b.

[1277] PLATE XXVI. FIG. 11.

[1278] Oliv. Ins. no. 19. Trogosita. t. 1. f. d. no. 41 bis. Dryops. t. i. f. 1. c.

[1279] See above, VOL. I. p. 238.

[1280] Oliv. Ins. no. 17. Ptinus. t. i. f. 1. c.

[1281] Ibid. no. 60. Blaps t. i. f. 2. c.

[1282] Ibid. no. 88. Languria. t. i. f. 2. c.

[1283] Ibid. no. 89. Erotylus. t. ii. f. 12. c.

[1284] Oliv. Ins. no. 41. Gyrinus. t. i. f. 1. e.

[1285] PLATE XXVI. FIG. 13. Hor. Entomolog. i. t. iii. f. 29, 30. E.

[1286] Mon. Ap. Angl. i. t. ii. Melitta. **. a. f. 2. t. v. Apis. *. b. f. 4. &c.

[1287] Oliv. Ins. no. 48. Cerocoma. t. i. f. 1. c.

[1288] PLATE XXVI. FIG. 10-12.

[1289] Clairv. Ent. Helvet. ii. Cicindela. t. xxiv. f. super. b. for Carabidæ, Dytiscidæ, his other plates.

[1290] Hor. Entomolog. i. t. ii. f. 13. E.

[1291] PLATE VI. FIG. 6, 12. f´´´.

[1292] Hor. Entomolog. t. i. f. 3. E.

[1293] Ibid. f. 4. E.

[1294] Oliv. Ins. no. 7. Hexodon. t. i. f. 1. e.

[1295] Ibid. no. 3. Scarabæus. t. l. f. 1. f.

[1296] Kirby in Linn. Trans. xiv. 102. t. iii. f. 4. d.

[1297] De Geer v. 417. t. iv. f. 12.

[1298] PLATES VI. VII. h´´.

[1299] See above, p. 443.

[1300] Mon. Ap. Angl. i. t. ix. 2. c. 2. β. f. 2. d. g. 4. t. xii. neut. f. 6. d. t. xiii. f. 3. b.

[1301] Clairv. Ent. Helv. ii. t. xxiii. f. 1.

[1302] PLATE VII. FIG. 3. b´´. h´´.

[1303] PLATE VI. FIG. 12. b´´. f´´´.

[1304] Ibid. FIG. 13. h´´. Savigny Anim. sans Vertèbr. l. i. 29--. t. i.-iii. ȯ.

[1305] De Geer vi. t. xix. f. 4. d.

[1306] Ibid. t. ix. f. 8. b b. t. xii. f. 20. b. t. xiv. f. 15. i i.

[1307] PLATE XXVI. FIG. 6.

[1308] Ibid. FIG. 5.

[1309] Kirby Mon. Ap. Angl. i. t. x. Apis. **. c. 2. δ. f. 3. a. and **. d. 1. f. 1. d.

[1310] Clairv. Ent. Helvet. ii. t. xxxi. f. super. b. Mon. Ap. Angl. i. t. xiv. f. 1. h. f. 3, 5. c.

[1311] See above, p. 317.

[1312] PLATE XXVI. FIG. 1. As the very remarkable maxillary palpi of that extraordinary Coleopterous genus Atractocerus seem not to have been so fully described as they deserve, I shall give here a minute detail of their composition. They consist of four joints: the first is wide and short, and somewhat platter-shaped; the second is much smaller and shorter: the third is concavo-convex, or shaped like a shallow bowl: towards the breast this joint is elevated, and on the elevated edge sits the last joint, which is longer than all the rest taken together. In my specimen it points towards the breast; its under side is entire and slightly curved, but in the upper side are two rows of lamellæ (b), placed alternately nine on each side, with an odd one at the end: these lamellæ are full of minute papillæ, and furrowed on the side next the mouth. From between the first pair a slender exarticulate hairy branch or appendage emerges (a), which forms nearly a right angle with the main stem. The labial palpi appear to consist of three joints; the two first very short, and the last large, ovate, and acute. This description is not taken from A. necydaloides, but from a Brazilian species more than five times its size, which I have named A. grandis.

[1313] PLATE VI. VII. XXVI. e´.

[1314] PLATE VI. FIG. 6, 12. e´. Cuvier Anat. Compar. iii. 347.

[1315] Cuvier Ibid.

[1316] Huber Fourmis, 4--.

[1317] Anim. sans Vertèbr. iii. 304.

[1318] See above, p. 440.

[1319] Reaum. v. 309--.

[1320] PLATE XXVI. FIG. 23.

[1321] Clairv. Ent. Helvet. ii. Pref. xxii.

[1322] Kirby Mon. Ap. Angl. i. t. xiv. (1) 2. b.

[1323] PLATE XXVI. FIG. 24. e´.

[1324] Clairv. ubi supr. t. xx. c.

[1325] PLATE XXVI. FIG. 28. e´.

[1326] Kirby ubi supr. fig. (8) 1. c c. The lateral pieces in the tongue in Vespa (Ibid. c c.) have been regarded as lobes of it, but they are rather Paraglossæ.

[1327] PLATE XXVI. FIG. 29. e´.

[1328] Clairv. ubi supr. t. xxx. c.

[1329] Kirby ubi supr. no. 2. f. 1, 3.

[1330] PLATE XXVI. FIG. 24. b.

[1331] Kirby ubi supr. t. x. Apis. c. 2. δ. f. 5. t. xii. neut. f. 2, 3. t. xiii. f. 1. h.

[1332] PLATE XXVI. FIG. 26, 29.

[1333] PLATE XXVI. FIG. 28. i´´.

[1334] Kirby Mon. Ap. Angl. i. t. xii. neut. f. 1. h h. t. xiii. f. 1. f f.

[1335] Ibid. t. x. **. d, 1. f. 2. b b.

[1336] See above, p. 425.

[1337] PLATE VII. FIG. 14. f´.

[1338] Reaum. v. 317.

[1339] Organisation exterieur des Ins. 184.

[1340] Ubi supra.

[1341] Anim. sans Vertèbr. I. i. 12.

[1342] De Geer ii. 778--. t. xxvi. f. 11. m. PLATE VII. FIG. 2. k´´.

[1343] Ubi supra.

[1344] See above, p. 455.

[1345] Organisation &c. 182.

[1346] Under this name M. Savigny includes the Myriapoda, Arachnida, and Crustacea. Anim. sans Vertèbr. I. i. 40.

[1347] Ibid. 43.

[1348] VOL. II. p. 275--. Also see above, p. 121--.

[1349] Anim. sans Vertèbr. I. i. t. ii. f. 2. a. a´.

[1350] PLATE VII. FIG. 13. c´.

[1351] Ibid. d´.

[1352] Anim. sans Vertèbr. I. i. 106. PLATE VII. FIG. 13. b´.

[1353] Ubi supr. 45--.

[1354] PLATE VII. FIG. 11. f´, a´´.

[1355] Ubi supra, 45.

[1356] Ibid. 44--.

[1357] N. Dict. d'Hist. Nat. ii. 275--. PLATE VII. FIG. 10. c´.

[1358] De Geer t. xl. f. 4. t. x. f. 7, 8.

[1359] See above, p. 18, 30.

[1360] Savigny Anim. sans Vertèbr. I. i. 62.

[1361] N. Dict. d'Hist. Nat. ii. 277.

[1362] N. Dict. d'Hist. Nat. ii. 276.

[1363] Ibid.

[1364] Ubi supr. 58.

[1365] PLATE XV. FIG. 7.

[1366] PLATE VI. FIG. 7-9. a´, b´, c´, d´.

[1367] Magaz. 1806.

[1368] PLATE VI. FIG. 7. a´.

[1369] Ibid. Labium b´. Mandibulæ c´. Maxillæ d´.

[1370] Savigny Anim. sans Vertèbr. I. i. 37.

[1371] De Geer iii. 137--. t. ix. f. 4.

[1372] Reaum. iii. 335. t. xxviii. f. 8-14.

[1373] De Geer iii. 117. t. viii. f. 22. b.

[1374] PLATE VII. FIG. 5, 6. a´, b´, c´, d´.

[1375] N. Dict. d'Hist. Nat. iv. 253.

[1376] PLATE VII. FIG. 5, 6. a´.

[1377] Ibid.

[1378] Reaum. iv. t. XVI. FIG. 13. z.

[1379] Authors are not agreed as to the precise number of lancets contained in a gnat's proboscis. Swammerdam affirms there are six, including the labrum. i. 156. b. t. xxxii. f. 3. Reaumur could find only five. iv. 597--. t. xlii. f. 10. And Leeuwenhoeck only four.

[1380] PLATE VII. FIG. 5.

[1381] PLATE VII. FIG. 5. This figure is copied from Reaumur, and was engraved before this discovery was made.

[1382] M. Savigny is of opinion that the central lancet or lancets represent the Epipharynx and Hypopharynx; for which he does not state his reasons: but as these are properly covers of the pharynx, the idea seems incorrect. Ubi supr. 15.

[1383] N. Dict. d'Hist. Nat. ix. 489. and iv. 253--.

[1384] Ubi supr. 36.

[1385] Ibid. t. iv. f. 1. o. o.

[1386] VOL. I. p. 48, 110--.

[1387] PLATE VI. FIG. 13. a´, b´, c´, d´.

[1388] VOL. I. p. 394--.

[1389] PLATE VI. FIG. 13. a´. Savigny Anim. sans Vertèbr. I. i. 3--. t. i.-iii. a.

[1390] Ibid. i. PLATE VI. FIG. 13. c´.

[1391] Ibid. FIG. 13. h´´. Savigny ubi supr. o.

[1392] PLATE VI. FIG. 13. d´. Savigny ubi supr. t. 1-3. o.

[1393] Ibid. ö. PLATE VI. FIG. 13. b´.

[1394] N. Dict. d'Hist. Nat. xvii. 467.

[1395] N. Dict. d'Hist. Nat. iv. 253.

[1396] PLATE VII. FIG. 8. c´, d´, e´, h´´.

[1397] Ibid, c´.

[1398] Ibid, d´.

[1399] Ibid, h´´.

[1400] Ibid. e´.

[1401] Rösel. ii. t. iii. f. 15. Latreille Gen. Crust. et Ins. iv. 365.

[1402] Swammerdam Bibl. Nat. t. ii. f. 4.

[1403] N. Dict. d'Hist. Nat. xxviii. 266.

[1404] Ibid. xvi. 432. De Geer vii. t. vi. f. 4. Not quite accurate.

[1405] PLATES VI. VII. XXVII. a.

[1406] Organisat. Extér. des Ins. 196.

[1407] In the Transactions of the Royal Society, this part in Anobium tessellatum is so called. xxxiii. 159--.

[1408] PLATE XXVII. FIG. 4. a.

[1409] PLATE VII. FIG. 2. a.

[1410] Observ. Nouv. sur les Hyménoptères (Ann. du Mus.) 5.

[1411] Those beetles whose posterior pair of tarsi have only four joints, and the two anterior five, are so called.

[1412] Kirby in Linn. Trans. xii. 464. t. xxiii. f. 6.

[1413] Ibid. xiii. t. i. f. 1. b.

[1414] PLATE VI. FIG. 10. g´.

[1415] Ibid. FIG. 7. a.

[1416] Ibid. g´.

[1417] PLATE VI. FIG. 4. g´.

[1418] PLATES VI. VII. b.

[1419] Kirby Mon. Ap. Angl. i. t. i. Melitta. *. b. f. 3.

[1420] PLATE VI. FIG. 4. b.

[1421] PLATES VI. VII. c.

[1422] VOL. II. p. 317--.

[1423] PLATE XXVI. FIG. 41. i.

[1424] Stoll Punaises, t. xxxix. f. 279, 280.

[1425] PLATES VI. VII. XXVI. d.

[1426] PLATES VI. VII. e.

[1427] PLATES VI. VII. f.

[1428] PLATE XXVII. FIG. 4. f.

[1429] Cuv. Regne Animal. iii. t. xiii. f. 4.

[1430] This insect was taken both at Matlock and Exmouth. The body and thighs are of a light-brown, wings testaceous, legs pale; antennæ between setaceous and filiform, two-thirds the length of the body; first joint not much thicker than the rest.

[1431] PLATE VI. VII. g.

[1432] De Geer iii. 561. t. xxvii. f. 1.

[1433] PLATES VI. VII. XXVI. h.

[1434] PLATE VII. FIG. 8, 9. XXVI. FIG. 43. h.

[1435] Viz. one on each side above, and one below.

[1436] Walckenaer Aranéïdes, t. v. f. 50, 52. t. viii. f. 82.

[1437] Treviranus (Arachnid. 4.) says that Scorpio Europæus has only two eyes. He appears to have overlooked the two on the anterior side of a tubercle at each angle of the head, where they are large, but not conspicuous, at least in my specimen.

[1438] De Geer vii. t. iii. f. 8, 9, 12.

[1439] PLATE XXVI. FIG. 43., h.

[1440] Walck. Aran. t. i. f. 3.

[1441] Ibid. t. v. f. 42-48.

[1442] Ibid. t. iv. f. 41.

[1443] Walck. Aran. t. i. f. 2.

[1444] Ibid. t. i. f. 7.

[1445] Ibid. t. ii. f. 18, 20.

[1446] VOL. I. p. 323.

[1447] De Geer vii. 138. t. viii. f. 15. y y.

[1448] Ibid. t. xl. f. 3. o o, y y.

[1449] PLATE XXVI. FIG. 43. h.

[1450] Segestria perfida, Walck. Aran. t. v. f. 52. &c.

[1451] Tetragnatha and Latrodectes, Ibid. t. vii. f. 64. and t. ix. f.. 84.

[1452] Nyssus coloripes, Ibid. t. vi. f. 58.

[1453] Dolomeda, Ibid. t. ii. f. 18, 20.

[1454] Sphasus, Ibid. t. iii. f. 24.

[1455] Mygale avicularia, Ibid. t. i. f. 3.

[1456] Sparasus, Ibid. t. iv. f. 41. PLATE XXVI. FIG. 37.

[1457] Eresus, Ibid. t. iii. f. 26.

[1458] Storena, Ibid. t. ix. f. 86.

[1459] Argyroneta, Ibid. f. 88.

[1460] Pholeus, Ibid. t. viii. f. 80.

[1461] PLATE XIII. FIG. 11.

[1462] PLATE XXIX. FIG. 11. h.

[1463] Ibid. a.

[1464] PLATE XIII. FIG. 10.

[1465] See above, p. 117--.

[1466] Reaum. iv. 245.

[1467] Microgr. 176.

[1468] Epist. Mar. 6. 1717.

[1469] Amœn. Academ. vii. 141.

[1470] I possess a specimen in which the eye is partly black and partly white: the lenses are invisible in the black part, but very visible in the white.

[1471] Philos. Entomolog. 19.

[1472] PLATE XXVI. FIG. 38.

[1473] Hooke Microgr. schem. xxiv.

[1474] PLATE XXIII. FIG. 3.

[1475] Cuvier Anat. Compar. ii. 442--. Compare Swammerdam Bibl. Nat. i. 211. t. xx. f. 45.

[1476] VOL. II. p. 4, 364, &c.

[1477] PLATE XXVI. FIG. 36. h. Fabricius, and after him Olivier, though both quote Forster, regard one of these eyes in Lamia Tornator as a spot; but they could not have examined it attentively. Saperda præusta F. has also four eyes.

[1478] PLATE XXVI. FIG. 39. h.

[1479] Latreille Gen. Crust. et Ins. iii. 73.

[1480] N. Dict. d'Hist. Nat. i. 479.

[1481] VOL. II. 320.

[1482] De Geer vii. 562.

[1483] VOL. II. p. 228.

[1484] Ent. Helvet. i. t. xii.

[1485] PLATE VI. FIG. 10.

[1486] Kirby Mon. Ap. Angl. i. t. xi. Apis. **. e. 1. f. 2.

[1487] De Geer iii. t. xxxiv. f. 17, 18, 24. o o.

[1488] Mon. Ap. Angl. i. t. xiv. no. 11. f. 1. f. Linn. Trans. xi. t. ix. f. 10. d.

[1489] PLATE XIII. FIG. 9. Fuessly Archiv. t. vi.

[1490] Schellenberg Cimices t. xiii. ix. f. 1. a. De Geer ii. t. xviii. f. 10.

[1491] Stoll Spectres, &c. t. iv. f. 14. t. x. f. 38, &c.

[1492] VOL. I. p. 261--.

[1493] Linn. Trans. ubi supr.

[1494] Schellenberg Mouches, t. xxvii. f. 1, 2. a, d.

[1495] Ibid. t. ix. f. 3. a.

[1496] Ibid. t. ii. f. 2. a.

[1497] Mon. Ap. Angl. i. 148.

[1498] PLATE XXVII. FIG. 4. h´.

[1499] This circumstance proves that Mr. W. S. MacLeay is correct in considering this as a subgenus; but it militates against its being connected with Lamprima.

[1500] PLATE VI. FIG. 4, 10. VII. FIG. 1, 2, 4. XXVI. FIG. 39-42. i.

[1501] Bibl. Nat. i. 214.

[1502] Reaum. iv. 245.

[1503] Ibid. v. 287--.

[1504] Magas. der Entomolog. iv. 410.

[1505] Latreille speaks of Phasma as having no stemmata; but it should seem that he examined only the apterous ones, all the winged individuals, at least so far as I have examined them, having three very visible ones. It may, I think, be laid down as a rule, that the larvæ and pupæ of Orthoptera have not these organs. Probably their use is principally in flying?

[1506] Flata phalænoides F. and affinities have no stemmata, while Flata reticulata and affinities have them: a proof that these tribes are distinct genera.

[1507] PLATE VI. FIG. 10. i.

[1508] Reaum. iv. 243. He refers for this insect to plate xiv. without adding any number for the figure; but no such is in that plate.

[1509] PLATE XXVI. FIG. 40. i.

[1510] Cercopis, Ibid. FIG. 42; and Fulgora, FIG. 41. i.

[1511] PLATE VI. FIG. 4. i.

[1512] PLATE XXVI. FIG. 40. i.

[1513] Ibid. FIG. 42. i.

[1514] PLATE XXVI. FIG. 41. i.

[1515] De Geer iii. t. xxvii. f. 1. Reaum. iii. t. xxxii. f. 3, 9.

[1516] PLATE XXVI. FIG. 40. i.

[1517] See above, p. 318--.

[1518] Linn. Trans. xiii.

[1519] Mag. der Entomolog. iv. 5.

[1520] Palpi quatuor, subæquales, cylindrici, ad basin clypei. Germ.

[1521] See above, p. 18, &c.

[1522] PLATE VI. FIG. 1, 4. i´.

[1523] See above, p. 321. Linn. Trans. xii. t. xxi. f. 3.

[1524] Ibid. f. 7.

[1525] PLATE VI. FIG. 4. c. i´.

[1526] PLATE XII. FIG. 9. l´´. This circumstance was very recently discovered; which will account for this plate not being quite correct in this respect, the bulb being represented as a distinct joint in FIG. 6, 10, 26.

[1527] See above, p. 498.

[1528] VOL. I. p. 231, 238.

[1529] Oliv. Ins. no. 80. Macrocephalus t. i. f. 1-4.; Anthribus f. 5-12; and no. 83. Curculio t. ii. Calandra f. 16.

[1530] Schellenberg Cimices t. xiv. f. 1. b.

[1531] De Geer vii. t. iv. f. 7. a a.

[1532] VOL. II. p. 421.

[1533] PLATES XII. FIG. 28; and XXV. FIG. 9, 24.

[1534] PLATE XXV. FIG. 4.

[1535] PLATES XII. FIG. 29; and XXV. FIG. 28. a.

[1536] PLATES XI. XII. XXV. k´´.

[1537] PLATES XI. XII. XXV. l´.

[1538] Ibid. m´.

[1539] PLATES XII. FIG. 28; and XXV. FIG. 13. m´´.

[1540] PLATE XXV. FIG. 2, 5, 21. m´´.

[1541] PLATE XII. FIG. 10. m´´.

[1542] Ibid. FIG. 4. m´´.

[1543] PLATE XXV. FIG. 1. m´´.

[1544] PLATE XI. FIG. 23.

[1545] PLATE XXV. FIG. 24.

[1546] Ibid. FIG. 30.

[1547] Jurine Hymenopt. t. vii. f. 3.

[1548] PLATE XXV. FIG. 28.

[1549] Ibid. FIG. 13.

[1550] Ibid. FIG. 5.

[1551] Ibid. FIG. 1.

[1552] PLATE XI. FIG. 12.

[1553] Linn. Trans. xii. t. xxi. f. 3.

[1554] Latreille says six, but only five are discernible; the three last form a kind of bristle.

[1555] Latr. Fourmis, 323.

[1556] Jurine Hymenopt. t. vi. f. 3.

[1557] Ibid. f. 2.

[1558] Ibid. f. 1. PLATE XXV. FIG. 7.

[1559] PLATE XXV. FIG. 25, 26.

[1560] PLATE XII. FIG. 16-22.

[1561] Ibid. FIG. 19. a.

[1562] Linn. Trans. xxii. t. xxi. f. 3, 4. PLATE XXV. FIG. 11.

[1563] PLATE XI. FIG. 17.

[1564] Kirby Mon. Ap. Angl. i. 184. t. x. **. d. 1. f. 8.

[1565] PLATE XXV. FIG. 27.

[1566] PLATE XII. FIG. 26.

[1567] PLATE XXV. FIG. 32.

[1568] PLATE XII. FIG. 25.

[1569] PLATE XXV. FIG. 17.

[1570] Linn. Trans. xii. t. xxiii. f. 5. f.

[1571] Ibid. t. xxi. f. 8 g. 9, 10. c.

[1572] De Geer iv. 219. t. viii. f. 20.

[1573] See VOL. II. p. 65, 201--.

[1574] De Geer iv. t. vii. f. 22.

[1575] PLATE XXV. FIG. 35.

[1576] De Geer vi. t. i. f. 5.

[1577] PLATE XI. FIG. 21.

[1578] PLATE XII. FIG. 29. a.

[1579] PLATE VI. m.

[1580] Ibid.

[1581] PLATE XXVII. FIG. 1, 3-5. n´.

[1582] Ibid. FIG. 3.

[1583] Ibid. FIG. 4.

[1584] PLATE XXVII. FIG. 1.