INSECTA

I N S E C T A.

THE animals which Linnæus included in his class Insecta have been distributed into four classes by modern naturalists. These are termed, Crustacea, Myriapoda, Arachnides, and Insecta. The distinguishing character of these different groups have already been laid before our readers under the article ANNULOSA, in which the systematical divisions of the three first have been pretty fully illustrated. In regard to insects, a reference was there made to the present article. In the fulfilment of our plan, we shall now take a view of the structure and physiology of insects; their classification, and the methods of preserving them for the cabinet, which are now in use.

The attention of naturalists, in general, has been confined to an examination of the forms of insects and the number of their parts. Their internal structure has been in a great measure overlooked, and little accurate information is known concerning many of their functions. The task, indeed, of examining the anatomy of insects is one of peculiar difficulty. The organs, in many cases, are complicated in their structure, and limited in size, so that in dissecting them, the point of a needle must frequently be employed instead of a scalpel, and the eye requires the assistance of high magnifiers. There are few, therefore, who have prosecuted this department of the subject with zeal or success, and who have inspired others with confidence in the accuracy of their statements. Swammerdam and Lyonet, however, form illustrious exceptions.

In the observations which we propose to lay before our readers in this article, we will confine ourselves, in the first place, to a brief exposition of the anatomy and physiology of insects, as the statements are given in considerable detail in the Encyclopædia, under the article ENTOMOLOGIE. It was necessary, however, to advert again to the same subject, for the purpose of noticing some of the recent discoveries which have been made by modern naturalists. In

VOL. V. PART I.

the second part of the article, there will be given an abridged view of the modern method of classifying insects. In the illustration of the first part of the subject, we shall begin by considering,

I.—The Organs of Protection and Motion.

The skin of insects serves the double purpose of protection and support, and represents the cutaneous and osseous systems of the vertebral animals. Its structure appears much more simple than in the higher classes, as it can neither be said to possess a mucous or cellular web or true skin. It bears the nearest resemblance to the cuticle of the skin of the higher classes, or rather, all the laminae of perfect skins are here incorporated into one uniform plate. It exhibits very remarkable varieties of texture. In some insects, as the house-fly, it is soft and pliable, while in others, as some of the weevils, it approaches the consistence of bone. In some species it is elastic, in others brittle.

The appendices of the skin consist of spines, hairs, and scales. The spines are merely projecting portions of its substance, and are usually distributed over certain parts of the feet, to aid the locomotive powers. Hairs are often distributed over the whole body; and, while they pass into spines on the one hand, they become, on the other, so exceedingly fine as to require the aid of a powerful magnifier to trace their character. These spines and hairs, being merely elongations of the skin, are not easily rubbed off. It is otherwise with scales. Some of these are inserted into their skin at their proximal, and are free at their distal extremity, and are so feebly connected, as to fall off, in many species, by touching them with the finger. These scales, in the butterfly, bear a remote resemblance to feathers in their form, and are very extensively used as pleasing objects for the microscope.

The MUSCLES of insects appear to possess the same internal structure as the same organs in the

higher classes. They are nearly all simple, and more or less transparent and whitish. All those which are concerned in the production of locomotion have their origin and insertion in the skin, apparently without the intervention of tendons. The different members appear to be connected with each other, by the intervention of a more transparent, tough substance, than the skin in other places, to which the name of ligament may be applied. The action of the muscles will be best understood by a description of the different parts of the body, and the motions which these perform.

1. The HEAD of insects contains the organs of the external senses and the mouth. It is joined to the trunk behind, and has its motions regulated by its mode of connection. Where the head is united to the trunk by a cylinder of ligament, the motion of which it is susceptible is various, limited chiefly in the dorsal direction by the superior margin of the trunk. When the articulation is effected by the immediate contact of the more solid surfaces, the three following modifications of joints present themselves. In the first, there are two or more rounded smooth tubercles, received into corresponding cavities in the trunk. The motion is consequently either backwards or forwards. In the second mode of articulation, the head is rounded posteriorly, and received into a socket in the thorax. In this manner great liberty of motion is obtained. In some cases, however, it is restrained by projections of the trunk, which limit it in one direction. In the third, the articulation takes place by the contact of two flat surfaces. The head is frequently contracted behind, and the trunk in front, to diminish the uniting surfaces, but such joint admits but of very imperfect motion.

The muscles of the head take their rise near the abdominal edge of the trunk, and, entering the occipital hole, become attached to its margin. Those which move the head upwards take their rise on the upper part of the trunk; while those which depress it arise from the under side. These last are the largest. Those which arise from the lateral parts of the trunk, give to the head its lateral motions.

The characters derived from the head, which are used in classification, are chiefly taken from the markings of its surface, the inequalities of its margin, its size, and shape. They are, in general, obvious and permanent.

2. The TRUNK, as an organ of support to the other members, may be considered as the most important part of the body. The terms, however, which are employed to designate its different parts are neither appropriate nor well defined. Linnaeus, in reference to this organ, gives the following enumeration of its parts: "Truncus, inter caput et abdomen, pedatus, thorace supra dorso, postice scutello, subtus pectore sternoque." By modern authors, it is usually divided into the thorax and breast.

The THORAX is the second ring of the body, and is united on the fore part with the head, and behind with the third ring or breast. In many species, this part is minute, while, in others, it occupies a large portion of the body. On its ventral aspect, it bears

the fore legs, or first pair, and between these is the thoracic sternum, frequently in the form of a keel, and terminating behind by a spinous process, which rests upon the pectoral sternum, as in the genera Elater and Dytiscus. It may be considered as the only fixed part of the body, giving origin to the muscles of the head, the fore legs, and frequently, also, to the breast and abdomen. Insecta.

The characters furnished by the thorax are extensively employed in the arrangement of insects. These are chiefly taken from its appearances on the back of the animal.

The BREAST is frequently so much incorporated with the thorax, as to appear as one organ. In other cases, it seems to form a part of the abdomen. In the back, it frequently exhibits a horny process, termed scutellum, analogous in consistence to the thorax, to which it is united behind. At this place of the breast, the wings have their origin. On its ventral side, it supports the middle and hind legs. Between these, at the base, is the pectoral sternum, which, in some species, expands into a cover for the first joint of the hind legs, and in others is produced to cover a portion of the abdomen. The breast contains the muscles for moving the middle and hind legs, the wings and abdomen; and it likewise contains some very strong muscles, passing from its ventral to its dorsal surface, and calculated to bring these, when required, nearer together. This motion is probably facilitated by the number of sutures with which its skin is traversed. The characters for classification are chiefly taken from the scutellum and sternum.

3. The ABDOMEN is the last portion of the body of insects. In some species, it is sessile, and intimately united with the breast; in others it is divided by a stalk. It consists of rings, varying in number in different genera. These rings are joined together in many species by a simple adhesion of the margin, while, in others, the posterior margin of the one includes the anterior margin of the other. The motion of the whole abdomen takes place by means of muscles, which arise in the breast, and, in those where it is sessile, the motion is very limited. The rings themselves are likewise susceptible of a little motion, especially when they are included. The muscular fibres which change their position are longitudinal, and pass from the posterior margin of one joint to the anterior of the other, and are able to draw the ring to one side, or pull it within the one which immediately precedes it.

The classical characters derived from the abdomen are chiefly taken from the number of the rings, their connection, and the condition of their surface. At the termination of the abdomen, the anus and external orifice of generation are situated. These have frequently appendices, which we will afterwards notice.

4. The MEMBERS of insects are of two kinds, wings and feet.

The wings vary in their number, structure, and appendices. In one class, they are wanting, and hence termed Apterous; in another they are two in number, but the greater number have four. These wings are either membranaceous, and supported by

Insecta. corneous ribs, which form a net-work in their substance; or, where the wings are four in number, the upper pair are sometimes crustaceous, obtain the name of elytra, and serve as a covering to the inferior ones. The ribs of the wings, improperly denominated nerves, in the manner of their distribution, the hairs by which they are covered, and the form of the vacant spaces, exhibit great regularity in the individuals of the same species. The manner in which the membranaceous wings are folded up, when at rest, is various. In some they are folded longitudinally, in others transversely, and in others obliquely. Each of these arrangements prevail throughout extensive groups. In the Diptera there is, under or behind each wing, a stalk terminating in a small knob. These are termed halteres, or poizers, and are considered as the rudiments of the second pair of wings. Between each poizer and the base of the wing, one or two spoon-like scales are found, termed winglets. They have likewise been observed in a coleopterous insect, Dytiscus marginalis. In some of the diptera they are absent. The use of these appendices of the wings has not been satisfactorily determined. The muscles which move the wings take their rise in the breast, and are capable of executing their functions with great celerity. The elytra perform no other motion than elevation and depression, and serve merely to protect the wings when at rest, not to assist them when flying.

The characters employed in the classification of the primary divisions of insects are, in a great measure, derived from the wings. Their presence or absence—their number and appendices—their texture and consistence, together with their size, position, and manner of folding up, yield marks which are of easy detection, and which experience has found to be permanent.

The legs of true insects are six in number. The first pair take their rise under the thorax, and the second and third pairs under the breast. They consist of the five following parts, the hip (coxa), the thigh (femur), the leg (tibia), the toe (tarsus), and the claw (unguis).

The hip, or coxa, serves to unite the limb with the body. It is usually short, or nearly as broad as it is long. It is imbedded in the thorax, or breast, and is limited in its motion by the mode of insertion. Sometimes its proximal extremity is globular, and received into a corresponding cavity of the body, giving to it a very extensive degree of motion. In other cases, the coxae of the hind legs are consolidated with the breast.

The thigh, or femur, is usually united with the coxa, in such a manner as only to admit of motion backwards and forwards. At its coxal extremity, the femur has, in some tribes, one or two eminences, in some cases produced into spines, which are termed trochanters, and as they are hollow within, they are considered as furnishing suitable insertions to the muscles for particular motions. When the thigh is slender and cylindrical, the motion of the legs is confined to walking, but where leaping is required, or even swimming, the thigh is thick, and bellied, to give room to the requisite muscles.

Insecta. The leg, or tibia, is articulated to the femur in such a manner as to admit of motion only in the same plane in which it moves. In those insects which swim, this joint is long and flattened, while, in those which dig holes in the ground, it is strong and serrated on the margin.

The toe, or tarsus, consists of several joints, which are articulated more loosely than the preceding parts of the limb, and admit not only of motion outwards and inwards, but likewise in a lateral direction. Its strongest muscle, as in the other parts of the leg, is the flexor. It is only by means of this part that the feet can apply closely to any object. The joints vary in number, length, and size; and, in many species, are furnished with very singular appendices. Those which deserve particular notice are denominated cushions and suckers, and are situated on the under surface of the joints. Accurate representations of these remarkable organs are given by Sir Everard Home, in the Philosophical Transactions for the Year 1816, (Plates XVIII.—XXI.), from the beautiful drawings of Mr Bauer.

The claw (unguis) is attached to the distal edge of the last joint of the tarsus. In a few species it is single, or capable of being opposed to a projection, serving the purpose of a thumb. In others, the claws are double, and either move in the same plane, or act in opposition. The muscles of the different parts are all included in the limb, except those of the coxae, which originate in the trunk. The former gives origin to those of the tibia, the latter to the first joint of the tarsus, and this again to the one which succeeds. These muscles are chiefly fixors and extensors, the former placed on the ventral, the latter on the dorsal surface of the limb.

From the enumeration which has now been given of the different organs calculated for the production of motion, we may see that insects are qualified for executing different kinds. Some indeed can only walk, others can walk and leap. Some can only walk and fly, others can walk, fly, and leap, while many can walk, fly, and swim, and, in addition, a few of these can leap.

II.—The Organs of Sensation.

The nervous system, in the class of animals now under consideration, exhibits a greater uniformity of structure and disposition than any of the other great systems of organs which they possess. The brain is situated in the head, on the dorsal surface of the gullet. It consists of two lobes, which exhibit slight variations of form, and are frequently so intimately united, that they appear as one, marked, however, in the middle by a groove. These lobes furnish the optic nerves, and frequently send filaments to the mouth. Near the posterior edge, two cords arise, which, after proceeding backwards, and, in many cases, embracing the gullet, unite to form a ganglion, from which nervous filaments proceed to the neighbouring parts. From this ganglion, two cords again proceed and form a second ganglion, and the same process is repeated until the cords reach the anal extremity, where they terminate. The number of ganglia which are formed, differ in different

genera, according to the number of articulations of the body. The cords, in some species, appear to unite and exhibit only the appearance of one.

The organs of the senses are more imperfectly developed in the insects than in the crustacea. The eye alone is the most perfect of any of these; and next to it may be classed the organ of touch. The existence of the other senses common to the vertebral animals, is rather inferred from the actions performed than from the structure of their parts.

It would lead into too extensive details were we to give an account of the various instincts which insects exhibit, the knowledge which they possess of external objects, and the indications of memory and reasoning which their actions intimate. Many of these have been already communicated under the articles ANT and BEE, and to the reader who is desirous of more information on the subject, we would recommend An Introduction to Entomology, by Messrs Kirby and Spence; two volumes of which have already appeared (1821), and the sequel is anxiously expected.

III.—Organs of Nutrition.

Under this division of our subject we include the alimentary canal, with all its appendices,—the vessels employed in circulation,—and those which are destined for aerating the blood.

1. ALIMENTARY CANAL. In treating of this important organ of nutrition in insects, it is necessary to begin with a description of the parts employed in obtaining and preparing food for the gullet. In many cases, as in the higher orders of animals, the legs, particularly the first pair, execute the first movement of seizing the food and conveying it to the mouth; in general, however, the parts of the mouth, unassisted, seize, cut, bruise, and prepare, the food for the gullet.

1. The masticating organs include the four following parts (which we shall designate by their Latin appellations for want of appropriate English terms), labrum, mandibulae, maxillae, and labium. These form the mouth, and are denominated Instrumenta cibaria.

The labrum is analogous to the upper lip of the higher classes of animals. It is articulated to the fore part of the head (frons, or clypeus, chaperon of the French), either directly by a simple suture, or by the intervention of a plate, to which Kirby, from its situation, has given the name nasus. The labrum itself, at its free edge, exhibits great variety of character in the condition of its margin, of which entomologists have availed themselves in the discrimination of species. This organ may be regarded as the cover to the other parts of the mouth above.

The mandibulae are two in number. They take their rise immediately below the labrum on each side. They exhibit very remarkable differences, in size, shape, and armature. They move horizontally, and serve to cut objects by their edges crossing like the blades of scissors.

The maxillae are likewise two in number. They are united to the cheeks immediately underneath the mandibulae, and between these organs and the labium. They are more complicated than the mandibulae.

On their inner margin they are usually covered with stiff hairs. Externally they support the palpi, which are articulated appendages, consisting of two or more joints. Each maxilla is furnished with one of these, rarely with two. The use of the palpi has not been determined, although it is probable that they serve as organs of smell, and perhaps also of touch.

The labium is analogous to the under lip, and closes the under side of the mouth, resting on the maxillae. Its free edge is variously marked, and there is usually a line in the middle indicating its tendency to be double. On each side it supports a palpus consisting of two or three joints. Its base is connected laterally by ligament, with the base of the maxillae, and behind with a fixed plate jointed to the head, and termed mentum, corresponding, in position, with the nasus of the labrum.

When all these parts bear such a proportion to one another as to be able to cut the substances on which the insects feed, and convey them to the pharynx, they are considered as in the most perfect condition. But all these parts in the different classes exhibit very remarkable modifications. There are many species, which are destined to live chiefly or exclusively on fluid substances, to whom such masticating organs would be unsuitable. Those which hold a middle station between the gnawers and suckers, have the labium transformed into a soft fleshy plate, like the tongue of quadrupeds (and hence frequently termed lingua), capable of licking, and of being rolled inwards when at rest,—as in the Hymenoptera, represented by the bee. In the genuine suckers, the organs of the mouth present two important modifications. In the first, the labrum is nearly obliterated; the labium is produced and either crustaceous (rostrum), or membranaceous (proboscis), with a groove on its upper side, for the reception of the four plates or hairs into which the two mandibulae and maxillae have been converted. These appearances are exhibited in the classes Hymiptera and Diptera. In the second, both the labrum and mandibles are nearly obliterated, and the labium is short and fixed; and the two maxillae are produced and so applied to each other as to form a sucker. This sucker is capable of being rolled up spirally, and as it appears in the Lepidoptera, the butterfly for example, is usually termed the proboscis or tongue.

All these different parts of the mouth, however much they may be modified in size and shape, may still be readily detected, either by their position or palpal appendages. We owe this discovery of the true nature of the parts of the mouth of insects and the other pedate annulosa to M. Savigny, who has accompanied his judicious observations with accurate representations of each organ, and its various changes in the Mémoires sur les Animaux sans Vertèbres, premier partie, Paris, 1816.

2. The orifice of the gullet is, in general, a simple aperture into which the food is conveyed chiefly by the agency of the maxillae. In some cases, however, chiefly among the Hymenoptera, there is an organ on the base of the mouth, more or less distinct, to which the term lingua ought to be restricted. M. Savigny calls it glossa or hypopharynx. On the

Insecta. dorsal margin of the opening there is likewise, in some cases, a particular process, which is denominated by the above naturalist epiglossa, or epipharynx.

The gullet itself is usually membranaceous, and is either simple or furnished with an enlargement, denominated the first stomach. In the true stomach the walls present the appearance of muscular fibres, and in some of the Orthoptera these bands cover the whole surface, forming a true gizzard, fortified with teeth or scales pointing backwards. The intestines are variously convoluted, and frequently, near the anus, exhibit an enlargement which has been denominated a rectum. In some cases the canal is furnished with one or more side pouches, or cœcæ, near the stomach.

The hepatic vessels (for there is no secreting organ which can be compared to a liver) have their origin in the fluid contents of the abdomen, and even send their capillary extremities to the remotest parts. They vary greatly in number and size. The walls are dense and cellular, and the bile which they secrete is yellow, brown, or white, according to the species. These vessels, in some, terminate separately, in others they unite into a common duct. The terminations vary greatly, being in different species at the pyloric extremity of the stomach, the middle of the intestine, or at the rectum.

In insects, neither absorbing nor circulating vessels have been detected, although anxiously looked for by many celebrated anatomists and microscopical observers. The nutritious portion of the food appears to be absorbed by the walls of the intestines, and discharged into the cavity of the body, where there are neither veins, arteries, nor heart. Towards the back, indeed, there is an obvious vessel, placed longitudinally, to which some have given the name of heart, but which is more generally denominated the Dorsal Vessel. This vessel is widest in the middle, and diminishes in size at each extremity. Its walls consist of two membranes, the internal one muscular, and the external one cellular. This last is so much crowded with tracheal vessels, as to appear to be entirely composed of them. All the coats are liberally provided with nervous filaments. This vessel is kept in its position by the tracheal tubes, and by muscular fibres, which, in general, are disposed in triangles, and increase in breadth from the superior part of the body to its inferior extremity.

The contents of the dorsal vessel are fluid, but of such consistence, that, when its coats are punctured, no liquid flows out. The colour is usually similar to the adipose matter which is collected on or near its surface, and differs according to the species. When placed under a microscope, this humour appears to consist of grains or globules, containing other globules. It mixes readily with water, and when dried, resembles gum.

The humour of the dorsal vessel is subject to

Insecta. some degree of motion, arising from the contractions which it experiences. These are irregular as to time, and proceed from the one extremity to the other, by stages usually corresponding with the rings of the animal, and strongest in the abdomen. The nerves do not appear to exercise any influence on these contractions. The muscular fibres and tracheal filaments appear to exercise the greatest control. These contractions, which in some species are little more than thirty in a minute, in others amount to one hundred and forty in number, according to the species, have been denominated pulsations, and the organ itself has been termed a heart. To that viscus, however, it bears no resemblance, except in its contractions, which are, however, irregular. It neither receives nor gives motion to any circulating fluid. Its use appears to be to imbibe and convert the fluid of the abdomen into fat, to serve as a supply in those numerous cases where much nourishment is suddenly required, as during the metamorphoses of youth, and the production of eggs in maturity. The peritoneal membrane appears destined to execute the same functions.*

If there is thus no heart, and no circulation of the nutritive fluid obtained from the food, in what manner is this fluid acrated? In reference to this subject, Cuvier justly observes, "le sang ne pouvant aller chercher l'air, c'est l'air qui va chercher le sang." (Leçons, IV. 165.) The object is accomplished by a very complicated apparatus. On each side of the body are small orifices, termed stigmata, differing in number according to the species. These are formed by a cartilaginous ring, and in some cases furnished with one or more valves. Each orifice is the extremity of a short tube, which opens internally into a cavity, one on each side of the body, and extending from the head to the tail. From these lateral cavities arise innumerable tubes, termed tracheæ, most numerous at the termination of the stigmata, which convey the air to every part of the body. To enable them to do this, their coats consist of an external and internal cellular membrane, with a middle layer, consisting of a cartilaginous string, spirally twisted, resembling the spiral tubes of plants. These tracheæ, by their number and subdivisions, convey air to every part of the body, and form, indeed, the great bulk of its contents. In what manner the vitiated air is expelled, has not been ascertained in a satisfactory manner.

From this view of the nutritive system in insects, it appears that the chyle is absorbed by the inner surface of the alimentary canal; that it exudes from its external surface into the common cavity; that the tracheæ aerate this mass; and that, while the dorsal vessel and the peritoneal membrane prepare fat, the hepatic filaments separate from it bile, and probably urine. The existence of this last excrementitious fluid is evinced by the presence of urea in the excrement.

* See "Observations on the Use of the Dorsal Vessel," by M. Marcel de Serres; translated in Annals of Philosophy, IV. p. 346; V. p. 191, 369; and VI. p. 34.

Insects have the sexual organs on different individuals, impregnation takes place internally by their union, and the females are all oviparous.

In the male, the sexual organs bear a closer resemblance to those of the mammalia than some of the higher classes. The testes may be regarded as two in number, situated one on each side of the abdomen. In some cases they appear a simple mass, while in others they are subdivided into a number of lobes, which may be regarded as so many separate organs. The spermatic ducts are two in number, varying greatly in length and the number of tubes, which, like roots, combine in their formation. They unite into a common duct near the penis; but, previous to doing this, they are joined by the ducts of the vesiculæ seminales, and other accessory tubes, which, in different genera, exhibit a great diversity of character. The penis is usually a simple tube, in some cases protected at the base by two scales, which separate upon entering the vagina of the female, and thus prepare a passage for the penis, and serve likewise for retention. The external opening is usually situated at the extremity of the abdomen, beside the anus. In the libellulæ, or dragon-flies, it is seated at the base of the abdomen.

The males of insects are seldom of so large a size as the females, and frequently exhibit peculiar characters in their abdomen, eyes, or antennæ, by which they may be distinguished.

The female organs exhibit fewer varieties of structure in the different genera than those of the other sex. The ovaria consist of numerous tubes, in which the eggs are prepared. These open into a common oviduct, terminating in the vulva. Previous to the termination of the oviduct, it receives the ducts of one or more vesicles. To the sagacity of John Hunter we owe our knowledge of the use of these: "In dissecting," says he, "the female parts in the silk moth, I discovered a bag lying on what may be called the vagina, or common oviduct, whose mouth or opening was external, but it had a canal of communication between it and the common oviduct. In dissecting these parts before copulation, I found this bag empty; and when I dissected them after, I found it full." (Phil. Trans. 1792, p. 186.) By the most decisive experiments, such as covering the ova of the unimpregnated moth, after exclusion, with the liquor taken from this bag in those which had sexual intercourse, and rendering them fertile, he demonstrated that this bag was a reservoir for the spermatic fluid, to impregnate the eggs as they were ready for exclusion, and that coition and impregnation were not simultaneous. It has not been determined, whether the same arrangement prevails in all insects. This is a very near approach to the external impregnation of the ova, as takes place in many fishes and reptiles.

The female insect may, in general, be distinguished from the male, by the superior size of the abdomen. In some cases, both males and females survive the process of generation, to repeat it again in another season. In other cases, the female only sur-

vives, while, in many, death ensues, upon the eggs being prepared and excluded.

The apparatus with which some insects are furnished, to enable them to place their egg in a proper situation, has been denominated the ovipositor. It is a continuation of the vulva, more or less strengthened by bony spiculæ, according to the nature of the substance it is destined to penetrate.

The period which elapses between the union of the sexes, and the laying of the eggs, extends to days in some, and even to months in others. The eggs themselves are either deposited at once, or at particular intervals. They are deposited under one or other of the following conditions. In the first, the egg, upon being deposited, is left to the influences of external circumstances, and the young, when hatched, to the resources of their own instinct. In the deposition of the egg, the wisest arrangements are made for the welfare of the young. The mother attaches them, in general, to those substances on which, upon being hatched, they are destined to feed. The butterfly attaches her eggs to a leaf; the flesh-fly deposits her's upon carrion; while others insert them into the young of other insects. Not a few females prepare a particular hole, in which they place the egg, and lay up for the young a suitable provision when they burst the shell. In the second, where the insects live in society, the eggs are deposited within the dwelling, and the young are reared and fed by the mother's care, or rather by barren females which act as slaves.

In the aphides, or plant lice, as they are called, the female retains the eggs at one time until they are hatched, and at another lays them like other insects. There is another circumstance no less remarkable in these insects,—one act of impregnation not only renders fertile the eggs of the individual, but the young produced from these eggs, and from the eggs of those, even until the ninth generation.

When the eggs are hatched, the young are termed grubs, maggots, caterpillars, or, technically, larvæ. In this state they are proverbially voracious, and their digestive organs are of much greater dimensions than when arrived at maturity. In the condition of larvæ insects possess a variety of members, as legs, suckers, hairs, and even stigmata, which they do not possess in their maturity. They are all, however, destitute of wings. Some of them live constantly in the water, instead of the land, their future residence,—swimming in youth, and flying in maturity. The food of the larvæ is often solid, requiring powerful jaws to gnaw it, while the food of the perfect insect is fluid, and sucked up. When the larva has attained a certain size, and acquired the requisite quantity of fat, having been nourished either by the food which it has acquired by its own industry, as the caterpillars, or by that which has been brought to its cell, as in the grub of the bee, it prepares to assume the forms of maturity, by passing through the third stage of existence as a pupa. In this state, the parts, which were suitable only in the larva condition, either become obliterated, or are changed into organs fit for maturity. The following conditions of the pupa state are recognised by naturalists:

1. Some insects of the apterous tribes, merely by repeated castings of the skin, arrive at the perfect state, without undergoing any sudden or remarkable change of form or structure. These are termed Pupæ completæ. They move and eat like the perfect insect.

2. Many insects, which have wings in the perfect state, are observed to obtain first the rudiments of them, and afterwards all their parts, and to assume the form of the perfect insect while passing through this period of youth, without any particular transformation. In this state they are called Pupæ semi-completæ. Like the pupæ completæ, they likewise move and eat like the perfect insect. In the different kinds of pupæ which remain to be considered, the animal neither eats nor moves. It derives its nourishment from its stores of fat.

3. After retiring to some suitable place, the larvæ of some insects cast their skin, and disclose the body of an ovate form, enveloped with a coriaceous covering, forming within separate sheaths for the different external organs. In this covering all the changes of form and structure take place, which prepare it for maturity. These are termed Pupæ incompletæ.

4. Other insects, likewise, upon changing their skin for the last time in their larva state, appear within a coriaceous covering, destitute, however, of any sheaths within for the external organs; these last being closely applied to the body. These are termed Pupæ obiectæ.

5. In the last form of the pupa, the skin, instead of casting, is changed into the coriaceous covering. Such are termed Pupæ coarctatæ.

All insects, which do not eat, and are motionless in the pupa state, are careful to retire to situations, sufficiently remote from enemies, of suitable temperature and moisture. In many cases, the larva forms an exterior covering, in which the pupa may be lodged with greater safety. This covering is in some composed of threads of the well known substance termed silk. Sometimes only one or two threads are required to keep the pupa in a proper position; in others, the silk is woven into cloth, or so matted together, as to resemble paper. These external cases are termed cocoons. The matter of which they are fabricated is prepared by two long tubes, which take their rise in the abdomen, enlarge as they approach the head, and terminate by a duct, which opens under the labium. By pressing the orifice of this duct to one place, and then to another, the larva draws out the tenacious threads.

The larvæ that live in cells ready fabricated for their reception, as the wasp and the bee, are not contented with these as a covering during the pupa state, but they line their sides and bottom, and cover their mouth with silk, thus making a complete cocoon. These, after the insect has been perfected, are left in the cell, and when it contains another larva, a second lining is likewise prepared. Each lining at the bottom, in the case of the bee, covers the excrement, which the animal had produced in its larva state. Hence, the walls of bee-combs appear double or treble; nay, John Hunter, by whom the appearance was observed, has counted twenty different linings in one cell. (Phil. Trans. 1792, p. 193.)

The external covering of the pupa, in some cases, consists of pieces of earth or dried leaves, curiously joined together, and cemented by an adhesive secretion.

After the insect has remained in a pupa state for a certain period, exceedingly different in the various tribes, it bursts forth from its confinement in its state of maturity. In this perfect condition it is termed the Imago. The organs of reproduction now speedily enlarge, and preparation is made to increase and multiply.

We now come to the second object proposed in Method of this article, the modern method of classifying insects. Classifying Insects. The arrangement of insects has occupied the attention of many acute and accomplished naturalists. As yet, however, a considerable difference of opinion prevails, as to the characters which should be employed in the formation of the orders and other subordinate divisions.

Since the days of Swammerdam, there have not been wanting naturalists who have regarded the metamorphoses of insects as furnishing the most suitable characters for primary divisions. But, instead of adopting the four forms of metamorphoses of that author, they have divided insects into such as do not undergo changes of form in the third or pupa state, and such as do undergo changes.

Linnaeus, to whom zoology in all its branches was greatly indebted, gave to insects a uniformity of nomenclature, and a methodical arrangement, greatly superior to all his predecessors. His primary divisions were taken from circumstances connected with the condition of the wings. The simplicity of this method, and the obviousness of the characters which have been employed, have obtained for this system a decided preference among the entomologists of Britain. Perhaps the strongest objection which can be urged against this method is its limited nature, arising from the great increase of species, and the consequent influx of new characters calling for the formation of additional divisions.

Fabricius introduced a method of classifying insects, founded on the organs of the mouth, which has met with many admirers. These instrumenta cibaria furnish permanent and definite characters, and exhibit, in the modifications which they present, marks well calculated for fixing the limits of species and genera. They are, however, in many cases minute; careful dissection is requisite for their display; and not unfrequently the aid of the microscope is necessary.

All the organs which compose the animal frame have certain mutual relations, so that any remarkable modification in the structure or functions of one set of organs is usually accompanied with corresponding changes in the other systems. Thus in the case of insects, when we observe any remarkable modifications taking place in the masticating organs, we observe equally remarkable variations in the locomotive organs, as these two systems of organs are correlative. Hence it happens that the divisions of the Linnean classification are frequently co-ordinate with those employed by Fabricius.

These considerations have induced modern ento-

mologists to combine the two systems of Linnæus and Fabricius, and to add that of Swammerdam. The characters employed by Linnæus occupy the first rank, because they are most obvious to the senses. Those of Fabricius are resorted to in cases where the locomotive organs do not furnish marks sufficiently characteristic.

In the following brief exposition of the modern state of the classification of insects, our notices must necessarily be confined within very narrow limits. It would extend this article to ten times its present bulk were we to attempt to detail the characters of the genera, much more to add an enumeration of the species. We the less regret this constraint, as the characters of the Linnean genera, and many of the species, with notices of their habits, have been presented to the reader in the Encyclopædia, under the article ENTOMOLOGU. In Plates XXIV. and XXV. of this Supplement, there have been given examples of one or more species in all the classes.

CLASS I.

COLEOPTERA.

The insects of this class have their integuments of a coriaceous consistence, approaching, in some genera, to the hardness of shell. The wings are four in number. The upper pair, denominated elytra, are of the same texture with the skin. They are convex above, concave below, and, when at rest, their mesial margins join by a straight suture. In some genera the elytra are inseparably united at their suture, and in others, the elytra at the base of the suture are in contact, or lap over each other, while at the extremity they recede from each other. The inferior pair of wings are membranaceous, strengthened by anastomosing ribs, and when at rest they are folded obliquely and transversely, and concealed under the elytra. When the insect is about to fly, the elytra are raised, and remain fixed while the under wings unfold and execute their motions. In some species, the under wings are imperfectly developed, or nearly obliterated, and, consequently, flying is impracticable. In such cases the elytra are cemented at the suture. The abdomen consists of six or seven rings more or less covered by the elytra, each of which have two sigmata, one on each side. The antennæ exhibit a great variety of character in their situation, length, form, and number of the joints. The eyes are compound and two in number. Each eye, in some, is divided by the continuity of the marginal band of the head. There are no ocelli. The instrumenta cibaria are formed for cutting and masticating solid substances. The food, however, which is consumed by them differs greatly, according to the species, in kind and consistence, so that all the parts of the digestive system exhibit extensive modifications of form. They are all oviparous. The larva is lengthened, frequently destitute of antennæ and eyes, of twelve or thirteen rings, with a scaly head, and the parts of the mouth similar to the perfect insect. It has usually six feet. After continuing months, or even years, in the larva state, it changes into a pupa obiecta, through the skin of which the different members may be distinctly perceived. The

coleoptera in their perfect state require a supply of food, and live to a greater age than other insects. They are very numerous in species and genera. Linnæus subdivided this extensive order into three groups, according as the antennæ were clavate, filiform, or setaceous. M. Geoffroy employed the number of joints in the tarsus as the basis of his subdivisions. This method, though it separates a very few naturally connected genera, and is liable to some exceptions, is nevertheless so simple and easy of application, that it has been universally received throughout Europe.

I. COLEOPTERA PENTAMERA.—Under this head are included those species which have five joints in each tarsus. The genera which they form are distributed by Lamark into three sections, according as the antennæ are filiform, including those which are moniliform and setaceous, clavate or lamellate. (Hist. Nat. des Animaux sans Vertèbres, Tom. IV. p. 439.) Latreille, whose industry and acuteness have contributed greatly to extend the limits of entomology, has subdivided them in the following manner. (Régne Animal, par M. Cuvier, III. p. 173.)

I. PENTAMERA CARNIVORA.—The distinguishing character of the insects here referred to, and one which is peculiar to them, is the possession of six palpi, in place of four, the ordinary number, two of these attached to the labium, and two to each maxilla. The maxillæ are hooked, and covered on the inside with stiff hairs or spines. They have two stomachs. The first is short and muscular; the second more produced, with villous walls. The hepatic vessels are four in number, and terminate at the pylorus. The antennæ are filiform or setaceous. The thighs, of the middle and hind legs, furnished with large trochanters. They are carnivorous both in their larva and perfect state. In the former the body consists of twelve rings, the head and the first ring scaly, with two short antennæ.

I. Carnivora Terrestria.—The feet are formed for walking. The mandibulæ are apparent, the body is oblong, and the eyes prominent. The intestine terminates in a large cloaca, with two vesicles secreting an acrid humour.

1. CICINDELIADÆ. The maxilla are furnished with an articulated claw. Mandibulæ prominent, straight, and denticulated; eyes large and full; labium short; the tibia of the fore legs destitute of a notch on the inner side. In the genera Manticora, Cicindela, Megacephala and Therates, the breadth and the length of the thorax are nearly equal, and all the joints of the tarsus are entire. In the genus Collyris of Fabricius, changed by Latreille into Collyris, the thorax is narrow, and produced, and the penult joint of the tarsus is bilobated.

2. CARABIDÆ. The maxillæ destitute of the articulated claw. In general, the head is narrower than the thorax, and the mandibulæ are destitute of teeth. This very numerous family has been divided by Latreille into seven sections.

1. The external maxillary and labial palpi, with the last joint equal or larger than the preceding. The tibiae of the fore legs have a deep notch on the inner side; elytra truncated or obtuse; labium entire and oval, or nearly square; the head is contract-

Insecta. ed behind; and, with the thorax, is narrower than the abdomen; the thorax is heart-shaped and truncated behind, and its length never exceeds, but frequently falls short of its breadth. This section includes the following genera: Anthis, Graphipterus, Brachinus and Lebia. This last genus has been subdivided into the following genera by Bonelli, viz. Hellus, Cymindus, Lamprias, Dromius, and Demetrus.

2. The genera of this section exhibit the same form of palpi and elytra. The head is deeply divided from the thorax, to which it is joined by a socket; the labium is furnished on each side with a lobe; the thorax is lengthened; the penultimate joint of the tarsi frequently bilobate. The genera are, Zephium, Galerita, Drypta, Agra, and Odacantha.

3. The palpi and tibiae present the same characters as the preceding. The elytra are not truncated; the suture of the mentum is obsolete. This includes the genus Siagona.

4. The genera of this section differ from the preceding ones, in the tibiae being denticulated externally. The second and third joints of the antennæ are nearly equal and moniliform; the elytra are entire, and the mentum articulated. This includes the genera Scarites and Clivina.

5. The elytra are entire; the mentum articulated; anterior tibiae entire externally, with short terminal spines; labium pointed in the middle, with lateral lobes. This section contains the genera Ozena, Morio, Aristus, Harpalus, Feronia, Licinus, Badister, Panagæus.

6. The elytra are entire, and the anterior tibiae very slightly, or not at all notched; labium pointed. This includes Cychrus, Pamborus, Calosoma, Carabus, Nebria, Omophron, Pogonophorus, Loricera, and Elaphrus.

7. In this last section, two at least of the exterior palpi are pointed at the extremity. The anterior tibiae are notched. Bembidion, Trechus, and Apolomus.

II. Carnivora Aquatica. The feet of the insects here referred to are formed for swimming. The mid and hind legs are compressed or ciliated; the mandibles are concealed; the terminal hook of the maxillæ bent from the base; the thorax is broad; they live in the water both in the larva and imago state. The larvæ are long and narrow, with twelve rings; the head large, with strong hooked mandibulæ, pierced at the apex. The body has six feet.

1. DYTICIDÆ. The antennæ are filiform, and longer than the head. In the males of many species, the three first joints of the tarsi of the mid and fore legs are dilated, and furnished with complicated suckers. In a few genera, the tarsi of the mid and fore legs have only four joints, as Hyphidrus and Hydroporus; in the others, the tarsi are entire, as Halipus, Pelobius, Noterus, Laccophilus, Colymbetes, Hydaticus, Acilius, and Dytiscus.

2. GYRINIDÆ. The antennæ are here clavate, with a subsidiary ciliated one at the base of each; each eye divided into two by the marginal band of the head. There is only one genus belonging to this family, Gyrinus.

II. PENTAMERA MICROPTERA.—The insects of

this division constituted the genus Staphylinus in the Linnean system. They are characterized by their filiform or moniliform antennæ, sometimes thickening a little towards the end. The body is narrow, and the elytra scarcely reach to half the length of the abdomen. The coxæ of the fore and mid legs are remarkably large. Two bags are protruded at pleasure from the anus. They run and fly readily. When pursued, they elevate their head and abdomen, and assume a very threatening attitude. They frequent moist places, in the neighbourhood of putrid animal or vegetable substances. A few are found in flowers, in pursuit of minute insects. Their first stomach is very short, and without folds; the second is long and villous, with a short intestine. The species are very numerous, and have been divided into many genera, which admit of the following distribution:

1. Head exposed, and separated from the thorax by an obvious mark. Among these there are some which have the labrum deeply divided into two lobes. The STAPHYLINIDÆ are distinguished by their filiform palpi, and consist of the following genera: Staphylinus, Pinophilus, and Lathrobium. The OXYFORIDÆ have the four palpi, or at least the labial ones, terminated by an enlarged joint, as in Oxyforus and Astraphæus. In other genera, the labrum is entire. In the PÆDERIDÆ, the maxillary palpi are nearly the length of the head, as in Pæderus, Evæsthetus, and Stenus. In the OXYTELIDÆ, the maxillary palpi are greatly shorter than the head, and the antennæ are inserted in front of the eye, as in Oxytelus, Siagonium, Omalium, Piestes, Proteinus and Lesteva. The ALEOCHARIDÆ differ from the preceding family in the antennæ being inserted between the eyes, as in Aleochara.

2. Head sunk in the thorax as far as the eyes. In the LOMECHUSIDÆ, the tibiae are entire, as in Lomechusa. In TACHINIDÆ, the tibiae are spinous, as in Tachinus and Tachyporus.

III. PENTAMERA SERRICORNUA.—The elytra cover the abdomen; the antennæ are usually filiform, or slightly clavate; and, in the males particularly, serrated, pectinated, or plumose. In some of the genera, the thoracic sternum is advanced in front, under the head, and likewise produced behind. This character is exhibited in those which have the mandibles notched or bifid at their extremity, as the ELATERIDÆ, a numerous family, in which the natural genera have not yet been established; and, in those which have entire mandibles, as BUPRESTIDÆ, having filiform palpi, and containing the genera Buprestis, Tracys, and Aphanisticus; and the MELASIDÆ, in which the palpi have an enlarged terminal joint, as Melasis and Cerophytum.

In those whose thoracic sternum is destitute of the singular character exhibited by the preceding families, there are several genera in which the mandibles are forked at the apex, or furnished with a tooth beneath. In some the body and elytra are soft. In these the head is furnished with a neck in LYMOXYLONIDÆ, in which the elytra do not embrace the abdomen, as Lymoxylon, Hylecætus, Attractocerus, and Cupes; and, in MASTIGOIDÆ, in which the abdomen is embraced by the elytra, as in Mastigus and Scydmanus. In others, the neck is concealed, as in

MALACHIUSIDÆ, which exhibit, as a peculiar character, four vesicles divided into lobes, under the thorax and the base of the abdomen, which can be withdrawn or exerted and inflated at pleasure. The MELYRIDÆ have the palpi filiform, as Melyris, Dasytes, and Drilus; while in CLERUSIDÆ, the palpi are securiform as Clerus, Tillus, and Enoplum.

In those families where the body and elytra are firm and crustaceous, the PTINUSIDÆ have the head and thorax narrower than the abdomen, with the antennæ about the length of the body as Ptinus and Gibbium; and the ANOBIUMEDÆ, having the thorax of the size of the abdomen, and the antennæ much shorter than the body, as Anobium, Ptilenus, and Dorcatoma.

There are several genera which agree with some of the preceding in the softness of their bodies, but whose mandibles are entire at the apex. In some of these the palpi are filiform, as in the CEBRIOSIDÆ, which have tarsal joints entire, as Cebrio and Hammonia; and in SCIRTESIDÆ, which have the penultimate joint of the tarsus bifid, as Scirtes, Elodes, Rhipicera, and Dascillus. In others, the palpi, especially the maxillary ones, become thicker towards the extremities. In the LAMPYRIDÆ the antennæ are approximate at the base, and the maxillary are longer than the labial palpi, as in Lampyrus, Lycus, and Omalisus. In the TELEPHORIDÆ, the antennæ at the base are remote, and the labial and maxillary palpi are nearly of equal length, as in Telephorus and Malthinus.

IV. PENTAMERA CLAVICORNUA.—The antennæ are here obviously club-shaped, perfoliated or solid, generally exposed at the base, and longer than the maxillary palpi. In a few genera, forming the family DRYOPSIDÆ, the first and second joints of the antennæ are enlarged, and the remainder form a club nearly solid, so that they appear three jointed; as Dryops, Hydera, and Heterocerus. In the remaining families, the antennæ increase more gradually from the base, and the club consists of several joints. In some of these the pectoral sternum is produced under the head towards the mouth. In the HISTENIDÆ, the mandibles are prominent, and the antennæ geniculated, as Hister, Abræus, Onthophilus, Dendrophilus, and Platysoma. In the BYRRHIDÆ, the antennæ are straight, as Byrrhus, Throscus, Anthrenus, Chelonarium, Nosodendron, Elmis, Macronychus, Geococcus, and Megatoma. In other genera, the pectoral sternum is abbreviated in the usual form, as the DERMESTIDÆ, which have the mandibles, short, thick, and straight, at the extremity, as Dermestes and Attagenus. In the remaining families, the mandibles are lengthened, compressed, and hooked, at their extremity. The NITIDULIDÆ, the mandibles are notched, bifid, or furnished with a tooth at their extremity, as Nitidula, Biturus, Cateretes, Micropapulus, Thymalus, Colobicus, Engis, Ips, Scaphidium, Scaphisoma, and Choleva. The SILPHIDÆ have the extremities of the mandibles entire, as Silpha and Necrophorus. The insects of this family are reputed to feed on carrion, and to dig under dead mice and moles, and bury them in order to feast upon them more securely. These statements are without foundation. They feed on maggots, and their pupæ; and, in penetrating the ground in search of

the last of these, they loosen the soil so much, that the dead animal sinks under, by its own weight, or, if light, is elevated on a hillock.

V. PENTAMERA PALPICORNUA.—The maxillary palpi nearly equal, or surpass the elevated antennæ in length. These last are inserted in a pit beneath an unusual production of the anterior margin of the head. In the HYDROPHILIDÆ, the first joint of the tarsus is abbreviated, and the legs are flattened, and formed for swimming, as Hydrophilus, Spercheus, Elophorus, and Hydræna. In the SPHERIDIADÆ, the five joints of the tarsus are distinct, as in Spheredium and Cercyon.

VI. PENTAMERA LAMELLICORNUA.—The insects of this division are readily recognized by their club-shaped antennæ, the extremity of which is divided into laminae, capable of receding or approaching at pleasure. The LUCANIDÆ differ from all the rest of this tribe in the laminae of the club of the antennæ, being placed (not as in the other families, approximating at the base, and opening and shutting like the leaves of a book, but) like the teeth of a comb, perpendicular to the axis, as Lucanus, Sinodendron, Esalus, Lamprina, Platyccres, and Passalus. In the COPRIDÆ, the membranaceous termination of the maxillæ is large and transverse; the antennæ have eight or nine joints; the labrum is concealed by the semicircular margin of the head; the mandibles are soft; and the last joint of the labial palpi comparatively small, as Copris, Aleuchus, and Aphodius. The GEOTRUPIDÆ have the terminal joint of the labial palpi as large as the preceding one; the antennæ have eleven joints, and the mandibles are horny, as Geotrupes, Lethrus, and Typhæus. In the SCARABIDÆ the antennæ have nine joints. The labium is concealed by the mentum, as Scarabeus, Trox, Egialia, Oryctes, Hexodon, and Rutella. The MELOLONTHADÆ have the mandibles greatly concealed by the head and the maxillæ, as Melolontha and Anoplognathus. In the GLAPHYRIDÆ the labium is advanced and divided into three lobes, as Glaphyrus, Amphicoma, and Anisonix. The TRICHIADÆ have membranaceous mandibles, as Trichius, Goliathus, Cetonia, and Crematoschalus.

II. COLEOPTERA HETEROMERA.—The insects belonging to this great subdivision have the tarsi of the fore and mid legs furnished with five joints, as in the preceding, but the tarsi of the hind legs have only four joints. In a few genera, as Rhinomacer, Rhinosisimus, and Stenostoma, constituting the family RHINOMACERIDÆ, the front of the head is advanced into a snout, on which are seated the antennæ. In the remaining genera, the front exhibits the usual characters. In some, the head is triangular, or heart-shaped, and is furnished with a neck, and the maxillæ have no corneous tooth on their inner edge. Among these, there are some which have the claws simple, as the PYROCHROIDÆ, with bilobate tarsi, including the genera Pyrochroa, Notoxus, Scraptia, and Dendrocera. In the MORDELLADÆ, in which the tarsi of the hind legs at least are simple, are included the Mordella, Rhipiphorus, Anapsis, Horea, and Apalus. Among others, the claws are double, or deeply divided. In the genus Tetraonix, the penultimate joint of the tarsi is bilobate, in the others entire. In the MYLABRIDÆ, the an-

Insecta. tennæ are thickened at the extremity, as in Mylabris, Hyleus, Cerocoma, while in the CANTHARIDÆ, the antennæ are of equal thickness throughout, or rather taper towards the point, as Cantharis, Meloe, Zonites, and Onas.

Among those genera which have the head oval and destitute of a neck, there are some which have the maxillæ furnished with a corneous tooth on the inner side. The elytra in some are free, and cover membranaceous wings, as the TENEBRIONIDÆ, including Tenebrio, Opatrum, Crypticus, Sarrotium, and Toxicum. In many other genera, the elytra are united, and the membranaceous wings are nearly obliterated. Some of these have the maxillary palpi filiform, with the last joint nearly cylindrical. The ERODIUSIDÆ have the maxillæ covered with the mentum, as Erodus and Pimelia. In the SCAURUSIDÆ, the base of the jaws are exposed, as Scaurus, Tagenia, Sepidium, Moluris, Tentyria, Hegester, Eurychora, and Akis. Others have the extremity of the maxillary palpi enlarged, or securiform. In the ASIDADÆ, the base of the maxillæ is concealed by a large mentum, as Asida and Chiroscelis. In the BLAPSIDÆ, the base of the maxillæ is exposed, as in Blaps, Misolampus, and Pedinus.

The genera, in which the maxillæ are destitute of a corneous tooth on the inner side, are likewise numerous. Many of them have the antennæ cylindrical, or slightly tapering. The MELANDRIADÆ have the penultimate joint of all the tarsi bilobate, as Melandria, Lagria, Calopus, Nothus, Odemera, Stenostoma, and Rynomacer. In the HELOPSIDÆ, the joints of the tarsi, at least those of the hind legs, are entire, as Helops, Serropalpus, Hallomenus, Pytho, Nilio, and Cistela. Others have the antennæ more or less club-shaped, and generally perfoliated. The HELEADÆ, including the genera Helea and Cossyphus, have the head concealed, or received into a notch in the front of the thorax. The remaining families have the head exposed and projecting. In the DIAPERIDÆ, the insertion of the antennæ is concealed by the lateral margin of the head, as in Diaperis, Hypophleus, Trachyscelis, Eledona, Cnodalon, and Epitragus. In the LEIODESIDÆ, the insertion of the antennæ is exposed, as in Leiodes, Tetratoma, Eustrophus, and Orchesia.

III. COLEOPTERA TETRAMERA.—The tarsal joints of all the feet are four in number. They are phytivorous, and live chiefly in wood or on flowers. In one extensive group, the head is produced in front, in the form of a snout. Among these there are two genera, Bruchus and Anthriscus, in which the snout is short, and the labrum and palpi distinct. In the remaining genera the snout is long, and the labrum and palpi obscure. In the CURCULIONIDÆ, including the genera Curculio, Rhynchænus, Cionus, Calandra, and Rhina, the antennæ are distinctly geniculated. The Brentusidæ have antennæ destitute of the knee, as Brentus, Orchestes, Rhamphus, Brachycerus, Cylas, Apoderus, Attelabus, and Apion. In another group, equally numerous, the forehead is of the usual size. Among these, there are some which have eleven joints in the antennæ, and the third joint of the tarsi bilobate. The antennæ, in some, terminate in a perfoliate club, as the EROTYLUSIDÆ, including Erotylus, Triplax,

Insecta. Lanugria, and Phalacrus. In others, the antennæ are filiform. In the CERAMBICIDÆ, the labium is dilated and heart-shaped at the extremity, including the genera Cerambix, Prionus, Callidium, Necydalis, Saperda, Lamia, Stenocorus, Leptura, together with Spondylis and Parandra. In the CHRYSOSELINIDÆ, the antennæ are shorter than in the preceding family, and the labium is plain. It includes the following genera, Chrysomela, Cassida, Cryptoccephalus, Clythra, Galeruca, Altica, Hispa, Crioceris, Donacia, and Sagra.

In those which have not eleven joints in the antennæ, and the third tarsal joints bilobate at the same time, there are some which have the third tarsal joints entire. The MYCETOPHAGIDÆ have eleven joints in the antennæ, as Mycetophagus, Uleiota, Cucujus, Agathidium, Zylophila, Meryx, and Trogossita. In the BOSTRICHIDÆ, the joints of the antennæ do not exceed ten, as Bostrichus, Cerylon, Nemosoma, Cis, Cerapterus, and Pausus. The SCOLYTUSIDÆ have the penultimate tarsal joint bilobate, as Scolytus and Phloiotribus.

IV. COLEOPTERA TRIMERA.—The tarsi in this division are all three-jointed. The antennæ are clavate. In the COCCINELLIDÆ, the antennæ are shorter than the thorax, as Coccinella and Chilocorus. In ENDOMYCHIDÆ, the antennæ are longer than the thorax, as in Endomylus, Lycoperdina, Dascarus, and Eumorphus.

V. COLEOPTERA DIMERA.—The tarsal joints are only three in number. The genera hitherto determined amount only to two, as Claviger and Pselaphus. The latter, however, has been recently constituted into a family, PSELAPHIDÆ, including Pselaphus, Euplectus, Bythenus, Arcopagus, Tychus, and Bryaxis.

CLASS. II.
STREPSIPTERA.

This class was instituted by Mr Kirby, one of the most acute and intelligent observers among the English entomologists. The elytra (if such they can be called) are coriaceous, and arise, not from the upper side of the breast, but from the base of the coxæ of the anterior pair of legs, consequently they are remote from each other. They first recede from the body, then approach, and lastly recede again, exhibiting a tortuous course. They do not cover the wings. These last are firmly membranaceous, and their ribs are simple, diverging from the base, and folding longitudinally like a fan. The parts of the mouth are obscure, apparently consisting of two minute two-jointed palpi and two maxillæ, thus intimating that the imago consumes but little food, and is short lived. The antennæ arise, each of them, from a common jointed base, and afterwards divide. The eyes are pedunculated, two in number, and compound, with elevated septa, dividing the hexagonal lenses; the terminal segment of the abdomen ends in a reflected process. The larva inhabits hymenopterous insects, in which it changes into a pupa coarctata with the head exerted.

This order contains only two genera, Stylops and Zenos. In the former, the upper branches of the antennæ are jointed, in the latter they are simple. The Stylops melitta and tenuicornis are natives of Britain.

Since the institution of this class, doubts have been entertained as to the propriety of denominating the twisted processes which arise from the sides of the thorax, elytra. Latreille and Lamarck, without indicating much reluctance to increase the synonyms of the science, or delicacy towards the naturalist who first instituted the class, have suppressed the term Strepsiptera, the former substituting that of Rhipiptera, the latter, with more classical propriety, Rhipidoptera (from ῥιπς), in reference to the fan-shaped wings.

In this class, the elytra are short, coriaceous, with a straight suture. The wings are membranaceous, with longitudinal ribs, connected in the margin by a transverse one; they are folded when at rest longitudinally and transversely. The mandibles are bidentate. The maxilla have a scaly cylindrical appendix or galea. There are no pyloric cæca. The tarsal joints are three in number. The metamorphosis is semicomplete. This class comprehends the following genera: Forficula, Labia, and Labidura.

The elytra, in the insects of this class, are coriaceous, and at their inner margin overlap each other. The under wings are membranaceous, and have numerous longitudinal ribs crossed alternately at right angles by an infinity of transverse ones, so that their reticulations, or little squares, are usually arranged like bricks in a wall; when at rest these are folded longitudinally, and unfold like a fan. The parts of the mouth are similar to the coleoptera, with the addition of the galea protecting the maxillæ at the sides. The alimentary canal is furnished with a membranaceous crop, and a muscular stomach, armed with corneous scales. The pyloric cæca receive the biliary vessels, and a few likewise terminate in the intestine. The larvæ exhibit a pupa semicomplete. In all the stages of existence they live on the land.

Among the Orthoptera, there are several genera with their wings, when at rest, roof-like. These have either the tarsi with four joints, as the LOCUSTIDÆ, or the tarsi have only three joints, as the ACHECTIDÆ, including the genera Acheta, Truxalis, Ziphicera, Acrydium, and Pneumora.

In the remaining genera, the wings are horizontal. Among these the GRYLLIDÆ, including Gryllus, Tridactylus, and Gryllotalpa, have the body not flattened, nor the sides truncated, but the abdomen is furnished with appendages. In the genus Blatta, the body is depressed, and the sides truncated, with abdominal appendages. The remaining genera, with horizontal wings, are destitute of the abdominal appendages. These are the MANTIDÆ, including Mantes, Empusa, Phasma, and Spectrum.

The insects of this class exhibit considerable differences with regard to their wings. In some, the

upper wings are true elytra, crustaceous, or coriaceous, with membranaceous extremities overlapping each other; while, in others, the upper wings are wholly membranaceous. In some of the genera, the males only are winged, or they are all apterous. They agree, however, in the characters exhibited by the parts of the mouth. These are formed for sucking. The labium is produced, with a canal on its upper surface, and consists of several joints. The mandibulæ and maxillæ appear like four hairs, which, by their union, form the haustellum. The labrum is more or less produced as a covering to the base of these organs. The palpi are nearly obliterated. The metamorphosis is here semicomplete. This class is divided into two orders, which, in the opinion of some naturalists, ought to be elevated to the rank of classes.

I. HEMIPTERA HETEROPTERA.—These have the elytra crustaceous at the base, and the extremities folding over each other, and membranaceous. The rostrum is attached to the front of the head. The first segment of the thorax larger than the second; ocelli, two. The Heteroptera admit of subdivision into the terrestrial and aquatic.

The terrestrial heteroptera have two ocelli, the antennæ exposed, longer than the head, and inserted between the eyes near the inner margin. Some of these have the labium of four joints, and the labrum long, subulate, and striated above. Among these the PENTATOMIDÆ have five-jointed antennæ, as Pentatoma, Cydus, Tetyra, and Elia. The COREIDÆ have only four joints in the antennæ, as Coreus, Berytus, Lygaeus, Capsus, Miris, and Mydocha. In another group, the labium consists of only three joints, sheathing the labrum, which is short. In the REDUVIADÆ, the rostrum is curved, as Reduvius and Plocaria; while in CIMICIDÆ it is straight, as in Cimex, Tingis, Aradus, and Phymata. In a third group the labium consists of two or three joints, and does not embrace the labrum, as the ACANTHIDÆ, including Acanthia and Galgulus.

The aquatic heteroptera live in or upon the water. They are destitute of ocelli. In the HYDROMETRIDÆ, including Hydrometra, Velia, and Gerris, the antennæ are long, and inserted between the eyes. In the remaining families, the antennæ are short, and inserted under the eyes, and are shorter than the head. In the NEPADÆ, the tarsi of the fore-legs are indistinct, as Naucoris, Nepa, and Ranatra. In the NOTONECTADÆ, the anterior tarsi are distinct, as in Notonecta, Plea, Sigara, and Corixa.

II. HEMIPTERA HOMOPTERA.—In the insects of this division, the rostrum seems to originate from the chin. The second segment of the thorax is as long as the first. There are two or three ocelli. The CICADIADÆ have three joints in the tarsi, the antennæ consist of six joints, and there are three ocelli, as Cicada. The FULGORADÆ have three tarsal joints, and only three joints to the antennæ, and two ocelli, as Fulgora, Flata, Issus, Tettigometra, and Delphax. The CERCOPIDÆ differ from the preceding in the antennæ being inserted between the eyes, as Cercopis, Etalion, Ledra, Membracis, and Tettigonia. The APHISIDÆ have two joints in the tarsi, as Aphis, Psylla, Thrips, and Aleyrodes. The COCCIDÆ can boast of only one tarsal joint, as Coccus.

CLASS VI.
TRICHOPTERA.

The wings of the trichopterous insects are four in number, and membranaceous. The upper ones are usually of a darker colour and firmer consistence than the lower ones. The ribs, which are usually hairy, are disposed longitudinally, and when they do anastomose, the intervening spaces are lengthened. The lower wings fold longitudinally. The mouth has a distinct labrum; the maxillary palpi have five joints. The labial palpi have only three joints, the last of which is a little enlarged. The maxillæ and labium are united, but do not form a sucker. There are two large compound eyes, and two ocelli. The legs are spinous, and the tarsal joints five in number. The larvæ live in the water in tubular dwellings, which they construct, and move about with, open at both ends, and consisting of bits of stick, sand, or shells. Hence, they are usually termed case worms. They change into a pupa incompleta in the tube, which they inhabited when larvæ, and when ready for exclusion, by means of the sheathed antennæ, and fore and mid-legs, crawl out of the water, throw off the covering, and become inhabitants of the land.

Dr Leach has subdivided this class into two families. The LEPTOCERIDÆ have the antennæ much longer than the whole body, as Leptocerus and Odontocerus. The PHYRGANIDÆ have the antennæ only the length of the body, as Phryganea and Linnephilus.

CLASS VII.
LEPIDOPTERA.

This extensive and beautiful class consists of the butterflies and moths. The wings are four in number, membranaceous in texture, irregularly ribbed, and covered with coloured scales, in the form of a farinaceous powder. The parts of the mouth are formed for suction. There are only vestiges of the labrum and mandibulæ. The maxillæ are produced, with a groove on the inner edge. When united, as they are naturally, they form a tubular proboscis, through which the animal obtains its food. The maxillary palpi are inserted upon the base externally, and are minute. The labium is short and without joints, and supports two obvious palpi with three joints. There are two compound eyes, and in some species two ocelli. The antennæ consist of many joints, and are usually much longer than the head. The segments of the thorax are united. The tarsal joints are six in number. The larvæ have six feet with claws, and from four to ten others on the posterior portion of the body, which they use as suckers. They are changed into a pupa obiecta. The genera are now divided into three orders, corresponding with the Linnean genera Papilio, Sphinx, and Phalæna.

I. LEPIDOPTERA DIURNA.—The upper wings, at least, in all the species are vertical in a state of rest, and the lower ones are destitute of hooks. The antennæ are clavated, or filiform, with hooked extremities. Among these, the PAPILIONIDÆ have the hinder tibiæ furnished with two spines, situated at the tarsal end, as in Papilio, Parnassius, Thais,

Pieris, Polyomatus, Heliconius, Danaus, Cethosia, Libythea, and Nymphalis. The HESPERIADÆ, including Hesperia and Urania, have four spines to the hinder tibiæ, two in the middle and two at the tarsal extremity, as in the remaining lepidoptera.

II. LEPIDOPTERA CREPUSCULARIA.—The wings are horizontal in repose, and the under ones are furnished with a spine under the base, at the external margin which enters a hook on the lower side of the upper wings, as in the following division. The antennæ are prismatic and fusiform. The GLAUCOPIDÆ have the antennæ bipectinated in the male at least, as Glaucopis, Stygia, and Procris. The antennæ, in the remaining genera, are simple in both sexes. The ZYGENIDÆ have the palpi slender and hairy, as Zygena, Sesia, and Macroglossum. The SPHINGIDÆ have large scaly palpi, as Sphinx, Smerinthus, and Castinea.

III. LEPIDOPTERA NOCTURNA.—The insects included under this division have setaceous antennæ, diminishing in thickness from the base to the point. Among these, there are several families, in which the wings, when at rest, fold round the body. The PTEROPHORIDÆ have the margins of two of the wings, at least, divided into processes at each rib, as Pterophorus and Orneodes. The other families of the division have the four wings entire. The TINEADÆ have only two palpi apparent, as Tinea, Yponomeuta, Oecophora, Lithosia, and Adela. In the ALUCITADÆ, there are four palpi apparent, as Alucita, Crambus, and Galleria. Other families have the wings at rest, lying upon the body without inclosing it, and by their union form a lengthened triangle. The AGLOSSADÆ have four apparent palpi, as Aglossa and Botys. The PYRALIDÆ have only two apparent palpi, as Pyralis, Hermenia, and Platypteryx. In the third division, the wings do not rest upon the body so as to form a triangle. This extensive family includes the following genera, Phalæna, Campea, Noctua, Callimorpha, Bombyx, Furcula, Hepialus, and Cossus.

M. Savigny has observed, that, in those cases where the maxillary palpi have only two joints, the proboscis is naked or pubescent; and when they consist of three joints, the proboscis is always scaly.

CLASS VIII.
NEUROPTERA.

The wings in this class are generally four in number, wholly membranaceous, transparent, and greatly reticulated by the anastomosing ribs. The under wings are either larger or longer than the upper ones. The labrum, mandibulæ, maxillæ, and labium, are of the ordinary size, and formed for cutting. There are two large eyes, and two or three ocelli. The segments of the thorax are united, support the six legs, and are distinct from the abdomen.

In some of the families, the antennæ are about the length of the head, subulate, and consist of from three to seven joints, the last of which is setaceous. Among these the LIBELLULADÆ, including Libellula, Aeshna, and Agrion, have three tarsal joints, the mandibulæ and maxillæ corneous, and the terminal ring of the abdomen, furnished with hooks or scales. In the EPHEMERADÆ, the mandibles are obscure,

the tarsal joints four in number, and the terminal ring of the abdomen furnished with setæ, as in Ephemera, Baetis, and Clocon.

In other families, the antennæ are much longer than the head, and consist of sixteen joints and upwards. Among these the PANORPADÆ, including Panorpa, Nemoptera, Bittaces, and Boreus, have the front produced into a snout. The remaining families have the front short. In the MYRMELIONEDÆ the antennæ are clavate, and the palpi six in number, as Myrmelion and Ascalapus. The two remaining families have filiform antennæ. The TERMESIDÆ have from two to three tarsal joints, as Termes and Psocus. The HEMEROBIDÆ have four or five tarsal joints, as Hemerobius, Raphidia, Mantissa, Scalis, Corydalus, Chauliodes, and Osmylus. The PERLADÆ, including Perla and Nemoura, have the inferior wings folded longitudinally.

CLASS IX.
HYMENOPTERA.

The wings are four in number, membranaceous, and divided into large unequal meshes by the anastomosing ribs. The under wings are the smallest. The organs of the mouth are adapted both for cutting and sucking. For the former operation the labrum and mandibulæ are sufficiently strong; while the maxillæ are, together with the labium, more or less produced, and by their union, form a sucker. They have two labial and two maxillary palpi. The eyes are large, and the ocelli three in number. The females are armed with a sting or piercer. Many of the species live in society, and exhibit, in the magnitude and regularity of their operations, the most striking displays of the attributes of the social instinct. The insects of this class admit of a division into two orders.

I. HYMENOPTERA TEREBRANTIA.—The females of this order are furnished with a produced ovipositor, frequently of sufficient strength to pierce the bodies in which the eggs are deposited. Among these, there are two families in which the piercer is tubular, and does not consist of separate valves. The CHRYSIDÆ have the piercer formed of the last rings of the body, retractile, and furnished with a small sting, as Chrysis, Parnopes, and Cleptes. In the OXYURIDÆ, the piercer is protuberant, without a sting, as Oxyurus and Drynus. In the remaining families the piercer consists of several valves. In some of these the abdomen is united to the thorax by a small portion of its transverse diameter. Among these there are some which have all the wings with ribs. The ICHEUMONIDÆ have upwards of twenty joints in the antennæ, as in the following genera, Ichneumon, Zorides, Crypturus, Agathis, Sigalphus, and Alysia. In the EVANIADÆ, including Evania and Fænus, the joints of the antennæ do not exceed fifteen in number. In others, the under wings are destitute of ribs. The CYNIPIDÆ have the antennæ broken, with from six to twelve joints, as Cynips, Leucopces, Chalcis, and Cynipsillum. The DIPLOLEPIDÆ have the antennæ straight, with from eleven to sixteen joints, as Diplolepis and Eucharis.

The remaining families have the abdomen united to the thorax by the whole of its transverse diameter.

In the SIREXIDÆ the piercer consists only of three valves, the lateral ones serving as sheaths, as Sirex and Oryssus. In the TENTHREDADÆ, including Tenthredo, Cimbex, Hylotoma, Xiphedria, and Pamphilus, the piercer consists of four valves, the internal pair serrated.

II. HYMENOPTERA ACULEATA.—In this order are included such as have no ovipositor or piercer. The abdomen in the females, however, is usually furnished with a sting, and poison bags. The antennæ have thirteen joints in the male, and twelve in the female. These may be again reduced into two divisions. In the first, the feet are not formed for collecting pollen, and the first tarsal joints are cylindrical. Among these, there are two families, in which the ocelli are indistinct, and the neuters or females are apterous. The FORMICADÆ, including Formica, Polyergus, Ponera, Myrmica, Atta, and Cryptocerus, have males, females, and neuters, the last of which are apterous. They live in societies. The MUTILLADÆ have no neuters, and the females are apterous, as Mutilla, Dorylus, and Labidus. They are solitary. The others have the ocelli distinct, and are all furnished with wings. Among these there are some families in which the wings are always expanded. In the SCOLIADÆ, the first segment of the thorax is large, and extends above to the base of the upper wings, as in Scolia, Tiphia, Sapyga, Thynnus, and Pampilus. In the SPHEXIDÆ, the first segment of the thorax is narrow and distant above from the base of the upper wings, as in Sphex, Bembex, Larra, Crabro, and Philanthus. There are other families in which the upper wings fold longitudinally. In the MASARIDÆ, the mandibles are narrow. There are only males and females, which are solitary, as Masaris, Synagris, Eumenes, and Zethus. In the VESPADÆ, which are social, there are males, females, and neuters; the mandibles are large, as Vespa and Polistes.

In nearly all the remaining genera, the hind legs are made for carrying pollen, having the first tarsal joint enlarged and compressed. Among these are some in which the tongue, or intermediate process of the labium, is as long, or longer than its sheath, and deflected when at rest. In the APIDÆ, which are social, there are males, females, and neuters, as Apis, Melepona, Bombus, Euglossa, Eucera, and Anthophora. While agreeing with the preceding in many particulars, the following genera are destitute of the expanded tarsal joint, for carrying pollen, Systropha, Panurgus, Zylocopa, Ceratina, Megachile, Philermus, and Nomada. Others have the tongue shorter than the sheath, as the ANDRENADÆ, including Andrena, Halectus, and Colletus.

CLASS X.
DIPTERA.

The insects of this class have only two wings; and, in a few instances, none. Many species are furnished with halteres, and squamulæ. The mouth is formed for suction. For this purpose, the labrum is more or less produced as a cover. The mandibulæ are obliterated, or in the form of threads. The maxillæ are produced into threads, and by their union in company with the mandibulæ, form the syphon. The labium is either double or single, and forms a

Insecta. sheath, destitute of joints, for the reception of the syphon. In some cases, there are two maxillary and two labial palpi. The larvæ are destitute of feet, and pass into pupæ oblecta, or coarctata. In this numerous division, the labium, or sheath, is univalve, in others it is bivalve. We shall now advert to the first of these.

Among those with a univalvular sheath to the proboscis, there are some in which this sucking organ is entirely withdrawn, when not in use. Some of these have the sucker consisting of only the produced maxillæ. The MUSCADÆ have the eyes sessile, as Musca, Tephritis, Myoda, Macrocera, Scenopinus. The ACHIASIDÆ have the eyes pedunculated, as Achias, Diopsis. The genus Oestrus, or Gad-fly, agrees with the muscadæ in habit, but the parts of the mouth are imperfect. Others have the sucker of four filaments, formed from the mandibulæ and maxillæ. In the SYRPHIDÆ, the front is produced like a beak, as Syrphus, Psarus, Chrysotoxum, Cerea, and Rhingia. In the APHRITIDÆ, the front is abbreviated, as Aphritis and Milesia. In the remaining genera of this group, the last joint of the antennæ is not simple, as in the preceding families, but annulated, and destitute of the lateral hair which they possess. These are termed STRATIOMYDÆ, and include the genera Stratiomys, Oxycera, and Nemotelus.

In the remaining families, with a univalvular sheath, the proboscis is always more or less protuberant. Among these, there are some which resemble the preceding families, in having only three joints in the antennæ. The CONOPSIDÆ have the sheath bent, and the sucker, with two filaments, as Conops, Zodion, Homoxis, Bucentes, and Myopa. The BOMBYLIDÆ have the sucker composed of from four to six filaments, and the sheath is destitute of large lips, as Bombylius, Ploas, Mithrax, Nemestrina, Panops, Cyrtus, Acrocera, Astomella; together with Empis, Asilus, and Dioctria. The TABANIDÆ have the sheath furnished with large lips, and the third joint of the antennæ distinctly annulated; as in Tabanus, Pangonia, and Cænomya; together with Pachystoma, Rhagis, Dolechopus, and Mydas. Others have six joints or more in the antennæ. Among these the BIBIONIDÆ have moniliform or perfoliated joints, about the length of the head, as Bibio, Scathopsis, and Simulium. The TRIPULIDÆ have filiform or setaceous tentacula, as Tipula, Cetenophora, Trichocera, Psychoda, Tanypus, Limonia, Hexatoma, and Culix, all of which are destitute of ocelli;

together with Asindulum, Ceroplatus, Mycetophila, and Rhyphus, which are furnished with ocelli.

In the remaining genera of this class, the sheath of the sucker is bivalve. HYPPOBOSCIDÆ have the head distinctly divided from the thorax, as in Hippobosca, Feronia, Ornithomyia, Craterina, Oxypteron, and Melophagus. In the genus Nycteribia, the head is united with the thorax.

CLASS XI.

APTERA.

Into this class we have placed tribes of insects, which differ greatly from each other in the organs of digestion; but which do not agree with any of the preceding classes. They possess one common character in wanting wings, in all the stages of their existence. They may be divided into three orders, which by some are elevated to a primary rank.

I. APTERA SUCTORIA.—The head, thorax, and abdomen intimately united. The mouth consists of two simple processes, the lowest of which is longest, and receives the superior one in a cavity in its upper side. On each side is a process of four joints covering the others. These unite to form a proboscis, which rests upon the sternum. Are the simple processes to be considered as the labrum and labium, and the articulated lateral ones as palpi, the mandibulæ and maxillæ being absent. The antennæ consist of four joints. This order contains at present only one genus, PULEX or Flea. There are several species. The P. irritans is every where common, and the P. fasciatus of Bosc may be met with on moles and mice.

II. APTERA THYSANURA.—The head in this and the following order is obviously separated from the thorax by a contraction or neck. The last segment of the body is furnished with long filaments. In the LEPISMADÆ the setæ of the tail are continually extended in the direction of the body, as Lepisma and Forbicina. In the PODURADÆ, the setæ, when at rest, are folded under the body, as Podura and Smythurus.

III. APTERA PARASITA.—The tail in this order is simple, or destitute of the filaments which distinguish the preceding. The NIRMIDÆ, including numerous species of lice which infest birds, and included in the genera Ricinus and Pediculus of authors, have the mouth furnished with two teeth. The PEDICULIDÆ have a tubular proboscis, and include the genera Pediculus, Phthirus, and Hæmatopinus. (Q.Q.)

DESCRIPTION OF THE PLATE.

1. A, The stag-beetle (Lucanus) seen on the back. (Class Coleoptera.) B, The under side, exhibiting the position of the legs, and on one side the pits for the reception of the coxæ. C, The parts of the mouth displayed; a, the labrum, with its broad nasus; b, the mandibulæ; c, the maxillæ, with their jointed palpi; d, the bifid labium, with the two palpi and broad mentum.

2. The parts of the mouth of Cimex nigricornis. (Class Hemiptera.) a, The articulated labium, with the edges at each side, and the first joint of each of

the antennæ. This is the sheath for the other organs, and exhibits the groove on its oral surface; b, the sucker viewed from above, covered at the base for one-third of its length, with the subulated labrum, and exhibiting, at the extremity, the straight united tip of the maxillæ, and the recurved ends of the mandibulæ; c, is a view of the same parts separated, with the labrum removed, to exhibit the expanded roots of the mandibulæ and maxillæ, the small opening of the pharynx, and the pointed lingua before it and between the maxillæ.