American insects

Front matter

PLATE I

Mary Wellman, del.

PLATE I.

Prefatory Note

If man were not the dominant animal in the world, this would be the Age of Insects. Outnumbering in kinds the members of all other groups of animals combined, and showing a wealth of individuals and a degree of prolificness excelled only by the fishes among larger animals, and among smaller animals by the Protozoa, the insects have an indisputable claim on the attention of students of natural history by sheer force of numbers. But their claim to our interest rests on securer ground. Their immediate and important relation to man as enemies of his crops, and, as we have come to know only to-day, as it were, as- a grim menace to his own health and life — this capacity of insects to destroy annually hundreds of millions of dollars’ worth of grains and fruits and vegetables, and to be solely responsible for the dissemination of some of the most serious diseases that make man to suffer and die, forces our attention whether we will or not. Finally, the amazing variety and specialization of habit and appearance, the extraor¬ dinary adaptations and “ shifts for a living” which insects show, make a claim on the attention of all who harbor the smallest trace of that “ scientific curiosity” which leads men to observe and ponder the ways and seeming of Nature. Some of the most attractive and important problems which modern biological study is attacking, such as the significance of color and pattern, the reality of mechanism and automatism in the action and behavior of animals as contrasted with intelligent and discriminating performances, the statistical and experimental study of variation and heredity, and other sub¬ jects of present-day biological investigation, are finding their most available material and data among the insects.

This book is written in the endeavor to foster an interest in insect biology on the part of students of natural history, of nature observers, and of general readers; it provides in a single volume a general systematic account of all the principal groups of insects as they occur in America, together with special accounts of the structure, physiology, development and metamorphoses, and of certain particularly interesting and important ecological -relations of insects with the world around them. Systematic entomology, economic entomology, and what may be called the bionomics of insects are the special subjects of the matter and illustration of the book. An effort has been made to put the matter at the easy command of the average intelligent reader ; but it has been felt that a little demand on his attention will accomplish the result more satisfactorily than could be done with that utter freedom from effort

VI

Prefatory Note with which some Nature-books try to disseminate knowledge. The few technical terms used are all explained in the text in connection with their first use, and besides are inserted in the Index with a specific reference, in black-faced type, to the explanation. So that the tyro reading casually in the book and meeting any of these terms apart from their explanation has only to refer to the Index for assistance. Readers more interested in accounts of the habits and kinds of insects than in their structure and physiology will be inclined to skip the first three chapters, and may do so and still find the rest of the book “easy reading” and, it is hoped, not devoid of entertain¬ ment and advantage. But the reader is earnestly advised not to spare the little attention especially needed for understanding these first chapters, and thus to ensure for his later reading some of that quality which is among the most valued possessions of the best minds.

In preparing such a book as this an author is under a host of obligations to previous writers and students which must perforce go unacknowledged. Some formal recognition, however, for aid and courtesies directly tendered by J. H. Comstock of Cornell University, whose entomological text-books have been for years the chief sources of knowledge of the insects of this country, I am able and glad to make. To my artist, Miss Mary Wellman, for her constant interest in a work that must often have been laborious and wearying, and for her persistently faithful endeavor toward accuracy, I extend sincere thanks. To Mrs. David Starr Jordan, who read all of the manuscript as a “general reader” critic, and to President Jordan for numerous sugges¬ tions I am particularly indebted. For special courtesies in the matter of illustrations (permission to have electrotypes made from original blocks) I am obliged to Prof. F. L. Washburn, State Entomologist of Minnesota (for nearly one hundred and fifty figures), Prof. M. V. Slingerland of Cornell University, Dr. E. P. Felt, State Entomologist of New York, Mr. Wm. Beutenmiiller, editor of the Journal of the New York Entomological Society, and Dr. Henry Skinner, editor of the Entomological Newrs.

Vernon L. Kellogg.

Stanford University, California,

Contents

CHAP. PAGE

I. The Structure and Special Physiology of Insects . . i

II. Development and Metamorphosis of Insects . . . 35

Chapter I

ERHAPS no more uninteresting matter, for the general reader or entomological amateur, can be written about insects than a descrip¬ tive catalogue of the parts and pieces of the insect body. And such matter is practically useless because it doesn’t stick in the reader’s mind. If it is worth while knowing the intimate make-up of a house-fly’s animated little body, it is worth getting this knowledge in the only way that will make it real, that is, by patient and eye-straining work with dissecting-needles and micro¬ scope. This book, anyway, is to try to convey some information about the kinds and ways of insects, and to stimulate interest in insect life, rather than to be a treatise on insect organs and their particular functions. Life is, to be sure, only the sum of the organic functions, but this sum or com¬ bination has an interest disproportionate to that of any of its component parts, and has an aspect and character which cannot be foretold in any com¬ pleteness from ever so careful a disjoined study of the particular functions. And so with the body, the sum of the organs: it is the manner and seeming of the body as a whole, its symmetry and exquisite adaptation to the special habit of life, the fine delicacy of its colors and pattern, or, at the other extreme, their amazing contrasts and bizarrerie, on which depend our first interest in the insect body. A second interest, although to the collector and amateur perhaps the dominant one, comes from that recognition of the differences and resemblances among the various insects which is simply the appreciation of kinds, i.e., of species. This interest expanded by oppor¬ tunity and observation and controlled by reason and the habit of order and arrangement is, when extreme, that ardent and much misunderstood and scoffed at but ever-impelling mainspring of the collector and classifier.

Of all entomologists, students of insects, the very large majority are col¬ lectors and classifiers, and of amateurs apart from the few who have “crawleries” and aquaria for keeping alive and rearing “ worms” and water-bugs and the few bee-keepers who are more interested in bees than honey, prac¬ tically all are collectors and arrangers. So, as collecting depends on a knowledge of the life of the insect as a whole, and classifying (apart from certain primary distinctions) on only the external structural character of the body, any detailed disquisition on the intimate character of the insectean insides would certainly not be welcome to most of the users of this book.

That insects agree among themselves in some important characteristics and differ from all other animals in the possession of these characteristics is implied in the segregation of insects into a single great class of animals- Class here is used with the technical meaning of the systematic zoologist- He says that the animal kingdom is separable into, or, better, is composed of several primary groups of animals, the members of each group possessing in common certain important and fundamental characteristics of structure and function which are lacking, at any rate in similar combination, in all other animals. These primary groups are called phyla or branches. All the minute one-celled animals, for example, compose the phylum Protozoa (the simplest animals); all the starfishes, sea-urchins, sea-cucumbers, and feather-stars, which have the body built on a radiate plan and have no back¬ bone, and have and do not have certain various other important things,, compose the phylum or branch Echinodermata; all the back-boned ani¬ mals and some few others with a cartilaginous rod instead of a bony column along the back compose the class Chordata; all the animals which have the body composed of a series of successive rings or segments, and have pairs of jointed appendages used as feet, mouth-parts, feelers, etc., aris¬ ing from these segments, compose the phylum Arthropoda. There are still other phyla — but I am not writing a zoology. The insects are Arthro¬ poda; and any one may readily see — it is most plainly seen in such forms as a locust, or dragon-fly, or butterfly, and less plainly in the concentrated knobby little body of a house-fly or bee — that an insect’s body shows the characteristic arthropod structure; it is made up of rings or segments, and the appendages, legs for easiest example, are jointed.

An earthworm’s body is made up of rings, but it has no jointed appendages. A worm is therefore not an arthropod. A crayfish, however, is made up of distinct successive body-rings, and its legs and other appendages are jointed. And so with crabs and lobsters and shrimps. And the same is true of thousand¬ legged worms and centipeds and scorpions and spiders. All these creatures, then, are Arthropods. But they are not insects. So all the back-boned animals, fishes, amphibians, reptiles, birds, and mammals are Chordates, but they are not all birds. The phylum Chordata is subdivided into or composed of the various classes Pisces (fishes), Aves (birds), etc. And similarly the phylum Arthropoda is composed of several distinct classes, viz.: the Crustacea, including the crayfishes, crabs, shrimps, lobsters, water-fleas, and barnacles; the Onychophora, containing a single genus (Peripatus) of worm-like creatures; the Myriapoda, including the thousand¬ legged worms and centipeds; the Arachnida, including the scorpions, spiders, mites, and ticks; and finally the class Insecta (or Hexapoda, as it is some¬ times called), whose members are distinguished from the other Arthroantennas pods by having the body-rings or segments grouped into three regions, called head, thorax, and abdomen, by having jointed appendages only on the body-rings composing the head and thorax (one or two pairs of appendages may occur on the terminal segments of the abdomen) , and by breathing by means of air-tubes (trachese) which ramify the whole interior of the body and open on its surface through paired openings (spiracles). The insects also have three pairs of legs, never more, and less only in cases of degeneration, and by this obvious character can be readily distinguished from the Myria¬ pods, which have many pairs, and the Arachnids, which have four pairs. Centipeds are not insects, nor are spiders and mites and ticks. What are insects most of this book is given to showing.

To proceed to the classifying of insects into orders and families and genera and species inside of the all-including class is the next work of the collector and classifier. And for this — if for no other reason — some further knowledge of insect structure is indispensable. The classification rests mostly on resemblances and differences in corresponding parts of the body, apparent in the various insect kinds. What these parts are, with their names and general characters, and what their particular use and significance are, may be got partly from the following brief general account, and partly from the special accounts given in connection with special groups of insects else¬ where in this book. A little patience and concentration of attention in the reading of the next few pages will make the reader’s attention to the rest of the book much simpler, and his understanding of it much more effective.

The outer layer of the skin or body-wall of an insect is called the cuticle, and in most insects the cuticle of most of the body is firm and horny in char¬ acter, due to the deposition in it, by the cells of the skin, of a substance called chitin. This firm external chitinized * cuticle (Fig. 2) forms an enclosing exoskeleton which serves at once to protect the inner soft parts from injury

FIG . 3. — Bit of body-wall, greatly magnified, of larva of blow-fly, Calliphora erythrocephala, ' to show attachment of muscles to inner surface.

and to afford rigid points of attachment (Figs. 2, 3 and 4) for the many small but strong muscles wdiich compose the insect’s complex muscular system. Insects have no internal skeleton, although in many cases small processes project internally from the exoskeleton, particularly in the thorax or part

* It is not certainly known whether the cuticle is wholly secreted by the skin cells, or is in part composed of the modified external ends of the cells themselves.

of the body bearing the wings and legs. Where the cuticle is not strongly chitinized it is flexible (Fig. 6), thus permitting the necessary movement or play of the rings of the body, the segments of the legs, antennae and mouth-parts, and other parts. The small portions of chitinized cuticle thus isolated or made separate by the thin interspaces or sutures

Fig. 4. — Diagram of cross-section through the thorax of an insect to show leg and wing muscles and their attachment to body-wall, h., heart; al.c., alimentary canal; v.n.c. ventral nerve-cord; w., wing; leg; m., muscles. (Much enlarged; after Graber.) Fig. 5. — Left middle leg of cockroach with exoskeleton partly removed, showing muscles. (Much enlarged; after Miall and Denny.)

are called sclerites, and many of them have received specific names, while their varying shape and character are made use of in distinguishing and classifying insects.

Fig. 6. — Chitinized cuticle from dorsal wall of two body segments of an insect, showing sutures (the bent places) between segmental sclerites. Note that the cuticle is not less thick in the sutures than in the sclerites, but is less strongly chitinized (indi¬ cated by its paler color).

The whole body is composed fundamentally of successive segments (Figs. 1 and 7), which may be pretty distinct and similar, as in a caterpillar or termite or locust, or fused together, and strongly modified, and hence dissimilar, as in a house-fly or honey-bee. The segments, originally five or six, composing the head, are in all insects wholly fused to form a single box-like cranium, while the three segments which compose the thorax are in most forms so fused and modified as to be only with difficulty distinguished as originally independent body-rings. On the other hand, in most insects the segments of the abdomen retain their independence and are more or prothorax^ labiaMk ■ palpi' ^

proboscis '

\ \ metathorax

\\ mesothorax

Ns ''.coxa

'' trochanter '''"femur

'abdomen compound eye, antennse.

tarsal segments

Fig. 7. — Body of the monarch butterfly, Anosia plexippus , with scales removed to show external parts. (Much enlarged.)

less similar, thus preserving a generalized or ancestral condition. On the

head are usually four pairs of jointed appendages (Fig. 8), viz., the

antennae and three pairs of mouth-parts,

known as mandibles, maxillae, and labium or

under-lip. Of these the mandibles in most

cases are only one-segmented, while the two

members of the labial pair have fused along

their inner edges to form the single lip-like

labium. The so-called upper lip or lab rum,

closing the mouth above, is simply a fold of

the skin, and is not homologous, as a true

appendage or pair of appendages, with the

other mouth-parts. In some insects with highly

modified mouth structure certain of the parts

may be wholly lost, as is true of the mandibles

of dobson-fly, Corydalis cor- in the case of all the butterflies. The head

nuta, female, showing mouth- bears also the large compound eyes and the

parts, lb., labrum, removed; . 0 ...

md., mandible; mx., maxilla; smaller simple eyes or ocelli (for an account of

li., labium; gl, glossse of la- the eyes see p. 30). Attached to the thorax are

mxf., palpus of maxilla; ant., three Palrs of kgs, whlch are jointed appendages, . antenna. homologous in origin and fundamental struc¬

ture with the mouth-parts and antennae, and two pairs of wings (one or

Fig. 8. — Dorsal asDect of head both pairs may be wanting) which are expansions of the dorso-laterai skin or body-wall, and are not homologous with the jointed' ventra appendages. The thorax usually has its first or most anterior segmentl the prothorax, distinct from the other two and freely movable, while the hinder two,» called meso- and meta-thoracic segments, are usually ? enlarged and firmly fused to form a box for holding and giving attachment to the numerous strong muscles which move the wings and legs. The abdomen usually includes ten or eleven segments without appendages or projecting processes except in the case of the last two or three, which bear in the female the parts composing the egg-laying organ or ovipositor, or

Fig. 9. — Head, much enlarged, of mosquito, Culex sp., showing piercing and sucking mouth-parts. (After Jordan and Kellogg.)

Fig. 10. — Head and mouth-parts of honey-bee, much enlarged. Note the short, trowel¬ like mandibles for moulding wax when building comb, and the extended proboscis for sucking flower-nectar. (Much enlarged.)

in certain insects the sting, and in the male the parts called claspers, cerci, etc., which are used in mating. On the abdomen are usually specially notice¬ able, as minute paired openings on the lateral aspects of the segments, the breathing-pores or spiracles, which admit air into the elaborate system of tracheae or air- tubes, which ramify the whole internal body (see p. 19).

Of all these external parts two groups are particularly used in schemes of classification because of their structural and physiological importance in connection with the special habits and functions of insect life, and because of the pronounced modifications and differences in their condition: these are the mouth-parts and the wings.

Insects exhibit an amazing variety in food-habit: the female mosquito likes blood, the honey-bee and butterfly drink flower-nectar, the chinch-bug sucks the sap from corn-leaves, the elm-leaf beetle and maple -worm bite and chew the leaves of our finest shade- trees, the carrion-beetles devour decaying animal matter, the house-fly laps up sirup or rasps off and dissolves loafsugar, the nut- and grain-weevils nibble the dry starchy food of these seeds, while the apple-tree borer and timber-beetles find sustenance in the dry wood of the tree-trunks. The biting bird-lice are content with bits of hair and feathers, the clothesmothi and carpet-beetles feast on our mgs and woolens, while the cigarette-beetle has the depraved taste of our modern youth.

Fig. ii.

Fig. ii. — Mouth-parts, much enlarged, of the house-fly, Musca domestica. mx.p., maxil¬ lary palpi; lb., labrum; li., labium; la., labellum.

Fig. 12. — Head and mouth-parts, much enlarged, of thrips. ant., antenna; lb., labrum; md., mandible; mx., maxilla; mx.p., maxillary palpus; li.p., labial palpus; m.s., mouth-stylet. (After Uzel; much enlarged.)

With all this variety of food, it is obvious that the food-taking parts must show many differences; one insect needs strong biting jaws (Fig. 8), another a sharp piercing beak (Figs. 9, 13, and 14), another a long flexible sucking proboscis (Figs. 10 and 16), and another a broad lapping tongue (Fig. 11). Just this variety of structure actually exists, and in it the classific entomolo¬ gist has found a basis for much of his modern classification.

Throughout all this range of mouth structure the insect morphologists and students of homology, beginning with Savigny in 1816, have been able to trace the fundamental three pairs of oral jointed appendages, the mandi¬ bles, maxillae, and labium. Each pair appears in widely differing condi¬ tions; the mandibles may be large strong jaws for biting and crushing, as with the locust, or trowel-like, for moulding wax, as with the honey-bee, or long, flat, slender, and saw-toothed, as with the scorpion-flies, or needle-like, as in all the sucking bugs, or reduced to mere rudiments or wholly lacking, as in the moths and butterflies. Similarly with the other parts. But by careful study of the comparative anatomy of the mouth structure, and par¬ ticularly by tracing its development in typical species representing the various types of biting, sucking, and lapping mouths, all the various kinds of mouth structure can be compared and the homologies or structural cor¬ respondences of the component parts determined. Figs.. 8 to 16 illustrate

Fig. 13. — Seventeen-year cicada, Cicada septendecim , sucking sap from twig. (After Quaintance; natural size.)

Fig. 14. — Section of twig of Carolina poplar showing beak of cicada in position when sucking. (After Quaintance; much enlarged.)

Fig. 15. — Mouth-parts, much enlarged, of net-winged midge, Bibicocephala doanei, female, md., mandible; mx., maxilla; mx.l., maxillary lobe; mx.p ., maxillary palpus; li., labium; hyp., hypopharynx; pg., paraglossa of labium; l.ep., labrum and epipharynx.

examples of different mouth structures, with the corresponding parts similarly lettered.

The most conspicuous structural characteristic of insects is their posession of wings. And the wings undoubtedly account for much of the success of the insect type. Insects are the dominant animal group of this age, as far as number of species constitutes dominance, their total largely sur¬ passing that of the species of all the other kinds of living animals. Flight is an extremely effective mode of locomotion, being swift, unimpeded by obstacles, and hence direct and distance-saving, and an animal in flight is safe from most of its enemies. The wings of insects are not modified true appendages of the body, but arise as simple sac-like expansions (Fig. 17) of the body-wall or skin much flattened and supported by a framework of io The Structure and Special Physiology of Insects strongly chitinized lines called veins. These veins are corresponding artic¬ ular thickenings, in the upper and lower walls of the flattened wing-sac, which protect, while the wing is forming, certain main tracheal trunks that carry air to the wing- tissue. After the wing is expanded and dry, the tracheae mostly die out, and the veins are left as firm thick- walled branching tubes which serve admirably as a skeleton or framework for the thin membranous wings. It has been found that despite the obvious great variety in the venation, or number and arrange¬ ment of these veins of the wing, a general typeplan of venation is apparent throughout the insect class. The more important and constant veins have been given names, and their branches numbers (Fig. 18). By the use of the same name or number for the corresponding vein throughout all the insect orders, the homologies or morphological correspondences of the veins as they appear in the variously modified wings of the different insects are made apparent. Many figures scattered through this book show the venation of insects of different orders, and the corresponding lettering and numbering indicate the homologies of the veins. As the wing venation presents differing conditions readily noted and described, much use is made of it in classification.

The differences in the wings them¬ selves, that is, in number, relative size of fore and hind wings, and in struc¬ ture, i.e., whether membranous and F i6 delicate, or horny and firm, etc., have

„ , „ . . . . , always been used to distinguish the

tig. io. — Sphinx moth, showing proboscis; J °

at left the proboscis is shown coiled up larger groups, as orders, of insects, on the under side of the head, the nor- and the first classification, that of mal position when not in use. (Large _ . . . .. . . .

figure, one-half natural size; small fig- Linnaeus (l75° aPP*)> divides the class

ure, natural size.) into orders almost solely on a basis

of wing characters. The ordinal names expressed, to some degree, the differences, as Diptera,* two-winged ; Lepidoptera, scale- winged ; Coleoptera, sheath-winged, and so on. As a matter of fact, there may be much differ-

* The derivation of the Linnaean ordinal names is given on p. 223.

ence in the wings within a single order; most beetles, for example, have four wings, but some have two and some none. There are indeed wingless species in almost every insect order. But a typical beetle has quite dis¬ tinctive and commonly recognized wing characters; that is, it has two pairs of wings, the fore pair being greatly thickened, and developed to serve as sheaths for the larger, membranous under-pair, which are the true flight wings. Similarly, practically all moths and butterflies have two pairs of

Fig. 17. — Wing of cabbage-butterfly, Pier is rapes, in early sac-like stage, tr., trachea;

tl., tracheoles; l.v., lines of future veins. (After Mercer; greatly magnified.)

Fig. 18. — Diagram of wings of monarch butterfly, Anosia plexippus, showing venation. c costal vein; s.c., subcostal vein; r., radial vein; cu., cubital vein; a ., anal veins. In addition, most insects have a vein lying between the subcostal and radial veins, called the median vein. (Natural size.)

membranous wings completely covered above and below by small scales, which give them their distinctive color and pattern.

The exoskeleton, or cuticle, of the insect body is sometimes nearly smooth and naked, but usually it is sculptured by grooves and ridges, punc¬ tures or projections, and clothed with hairs or those modified flattened hairs known as scales (especially characteristic of butterflies and moths). This clothing of hairs or scales, or the skin itself, is variously colored and pat¬ terned, often with the obvious use of producing protective resemblance or mimicry, but often without apparent significance. (For an account of the colors and patterns of insects and their uses see Chapter XVII.) The hairs may serve for protection, or may be tactile organs, or even organs of hearing (see p. 26). The projecting processes may be spines or thorns or curious and inexplicable i 2 The Structure and Special Physiology of Insects

knobs and horns. The rhinoceros-beetle (Dynastes) (Fig. 19) and the sacred scarabeus are familiar examples of insects with such prominent processes.

The insect body, as a whole, appears in great variety of form and range of size, as our knowledge of the variety of habit and habitat of insects would lead us to expect. In size they vary from the tiny four-winged chalcids which emerge, after their parasitic immature life, from the eggs of other insects, and measure less than a millimeter in length, to the giant Phasmids

Fig. 19. — Rhinoceros-beetle, Dynastes tityrus, showing chitinous horns.

(walking-sticks) of the tropics, with their ten or twelve inches of body length, and the great Formosan dragon-flies with an expanse of wing of ten inches. A Carboniferous insect like a dragon-fly, known from fossils found at Commentry, France, had a wing expanse of more than two feet. Insects show a plasticity as to general body shape and appearance that results in extreme modifications corresponding with the extremely various habits of life that obtain in the class. Compare the delicate fragility of the gauzy¬ winged May-fly with the rigid exoskeleton and horny wings of the water-beetle; the long-winged, slender-bodied flying-machine we call a dragon¬ fly with the shovel-footed, half-blind, burrowing mole-cricket; the plump, toothsome white ant that defends itself by simple prolificness with the spare, angular, twig-like body of the walking-stick with its effective protective resemblance to the dry branches among which it lives. Compare the leg¬ less, eyeless, antennaless, wingless, sac-like degraded body of the orange-scale with the marvelous specialization of structure of that compact expo¬ nent of the strenuous insect life, the honey-bee; contrast the dull colors of the lowly tumble-bug with the flashing radiance of the painted lady-butterfly. But through all this variety of shape and pattern, complexity and degenera^ tion, one can see the simple fundamental insect body-plan; the successive segments, their grouping into three body-regions, the presence of segmented appendages on head and thorax and their absence on abdomen (except perhaps in the terminal segments), and the modification of these append¬ ages into antennae and mouth-parts on the head, legs on the thorax, and ovipositor, sting, or claspers in the abdomen.

In the character of the structure and functions of the internal organs

The Structure and Special Physiology of Insects i 3 or systems of organs of insects, a special interest attaches to the conditions shown by the circulatory and respiratory systems, and by the special sense-

Fig. 20. — Diagram of lateral interior view of monarch butterfly, Anosia plexippus , show¬ ing the internal organs in their natural arrangement, after the removal of the right half of the body-wall together with the tracheae and fat body; I to III, segments of the thorax; i to 9, segments of the abdomen. Alimentary Canal and Appen¬ dages: ph., pharynx; sd. and sgl., salivary duct and gland of the right side; oe., oesophagus; f.r., food-reservoir; st., stomach; i., small intestine; c.} colon; r.} rec¬ tum; a., anus; m.v., Malpighian tube. Haemal System: h., heart or dorsal vessel; ao., aorta; a.c., aortal chamber; Nervous System (dotted in figure): br., brain; g., suboesophageal ganglion; l.g., compound thoracic ganglia; ag.v ag.4, first and fourth abdominal ganglia. Female Reproductive Organs: cp., copulatory pouch; v., vagina; o., oviduct, and 00., its external opening; r.ov., base of the right ovarian tubes turned down to expose the underlying organs; l.ov., left ovarian tubes in posi¬ tion, and ov.c., their termination and four cords; sp., spermatheca; a.gl. v part of the single accessory gland; a.gl.2, one of the paired accessory glands; only the base of its mate is shown. Head: a., antenna; mx., proboscis; p., labial palpus. (After Burgess; three times natural size.)