Entomology

ENTOMOLOGY. This is the science which treats of the habits, transformations, and physical .structure of insects; or the science or natural history, and description of insects. An insect is an articulate animal form, having the body com posed of three distinct parts, the head, corslet or thorax, and abdomen; the legs are six in num ber with, usually, two/or four wings attached to the thorax; and, along the sides of the abdomen minute punctures, called spiracles, by means of which respiration takes place. Formerly spiders, and crustacea, and even worms and other small animals, were included under the term insect. The term is now restricted to the hexapods, or the six-footed species, known as beetles, bugs, bees, grasshoppers, locusts, fleas, etc., primarily produced from eggs, whatever secondary modes of propagation may take place. The egg state 'constitutes one of the most important epochs in insect life, since on this depends all the subse quent states and developments affecting devel opment and decay. From the egg the larva is produced, The late and lamented Dr. 'Le Baron, has carefully and tersely described the outlines of Entomology, and insects in 'general, in one of his valuable reports: From it we extract : Insects as a class, and in the meaning of the word, comprise three divisions, or sub-classes, com monly known as spiders, insects and millipedes. They may be distinguished by the following characters : 1. Sub-class : Arachnids, including spiders, scorpions and Acari, or mites. Body divided into two parts, the head and thorax being united in one; legs eight in number; without wings. 2. Sub-class; Dakota, or insects proper. Body divided into three parts, the head, the thorax, and the abdomen ; legs six; furnished with wings, in the perfect or imago state. 3. Subclass: Ilfyriapoda, commonly called milli pedes or centipedes.. Body divided into many parts or segments, varying from ten to two hun dred; legs numerous; usually either one or two pairs of legs to each segment of the body; never have wings. The exceptions to these characters are very few. In the Arachnids, some of the most minute (Acari) have but six legs. Insects proper are always six-legged in their last or perfect state; and they also generally have six true legs in' their larva state; but some larvEe have no legs, and the larva of the Lepidoptera, com monly called' caterpillars, have, in addition to their six true legs, several pairs of false legs, or pro-legs, which assist in locomotion. There are a few exceptional cases in which insects are des titute of wings. The fleas (Pulices), the lice (Pediculi), and the little family of insects known as spring-tails (Thysomoura)„ never have wings In some rare instances the females are wingless, whilst the males have wings. This is the case with some species of the lightning-beetles (Lam pyridce), and with the canker-worm moth, and the tussock-moth, and a few other species amongst the Lepidoptera. Similarly exceptional cases are also found in other orders of insects The present work treats only of insects proper. The nervous system of insects consists of a double cord extending the length of the body, and lying upon the inferior or ventral side of the internal cavity. The two threads which com pose this cord do not lie side by side; but one above the other. The lower thread swells at intervals into little knots of nervous matter, called ganglia. In insects of an elongated form, such as some of the Neuroptera, and the larvae of the Lepidoptera, there is a ganglion at each segment of the body, making thirteen in all; but in most mature insects the ganglia become more or less consolidated. In, the butterfly (Popilio), there are ten ganglia, counting the brain as one; in the bee (Apis), there are eight; in the may beetle (Xelolontlta), there are five, and in the Cicada there are but two. The upper 'of the two nervous threads runs nearly in contact with the lower, but is destitute of ganglia., These two threads seem to represent the double and more compact cord which constitutes the spinal mar row of the higher or vertebrated animals. The upper simple thread is supposed to furnish the nerves of motion, and the lower and ganglionic thread, the nerves of sensation. The fibres which compose these cords separate at the anterior extremity of the body, so as to embrace the oesophagus or gullet, above which they again unite form the cerebral ganglion or brain, which is somewhat larger than the other gang lia From the nervous cords, and chiefly from the ganglia, fine lateral threads are emitted, which are distributed to the adjacent parts. The nerves thus far described represent what, in the higher animals, is called the cerebrospinal system of nerves, and are sometimes called the nerves of relation, because they control the sensations and motions which associate the animal with the world around it. But in addition to these, there have been discovered a number of very fine nervous filaments proceeding from the brain, and extending down into the body, and furnished with minute ganglia of their own, which are supposed to represent the sympathetic system of nerves which preside over the internal functions, such as those of digestion and secre tion. The blood of insects is a colorless fluid, which does not circulate in closed vessels or tubes, like that of the higher animals, but permeates the tissues of the body. The only vessel ihat can he discovered is all oblong, membranous, pulsating sac, situated in the upper or dorsal part of the body, and evidently represents the heart. This is divided into several compartments by cross• valves, which are so arranged as to permit the blood to pass only in a forward direction. The heart is prolonged anteriorly into a narrower tube analogous to the aorta. Through this the blood flows first towards the head and thence through the body, returning to the heart, which it enters through openings at its sides. As compared with that of the warm-blooded animals, the blood of insects is not only colorless, but small in quantity, and must circulate very slowly, as is proved by the fact that when their bodies are wounded no blood escapes. Most of the organs of insects, and their functions, have an obvious analogy to those of the higher animals, but their breathing appara tus is constructed upon an entirely different plan. In all the vertebrated animals the blood is carried in vessels to a particular part or organ of the body, for the purpose of being exposed to the life-giving influence of the air. This part in terrestrial ani mals, is the lungs, and in aquatic animals the gills. But in insects the process is reversed, and the air is carried to the blood by being distributed to every part of the body in very delicate pearl white tubes or vessels, which present a beautiful appearance under the microscope. They are called tracheae, or air tubes. They admit the air through little openings along the sides of the insect's body, called spiracles. The spiracles or breathing pores can be easily seen along the sides of all caterpillars which are not too densely cov ered with hairs. In the perfect or winged state of insects the branches of the air tubes are dilated into a great number of little vesicles or air blad ders, which render their bodies lighter, and thus facilitate their flight. In some aquatic larvm the tracheae project from the body in the form of lit tle tufts, analogous to the gills of fishes. The aquatic beetles are under the necessity of rising to the surface, at intervals, for air, in a manner similar to that of the aquatic mammalia, the whales and the dolphins. The digestive appara tus of insects, like that of other animals, consists of an elongated tube called the alimentary canal, extending through the body, and having a num ber of enlargements in its course, and in many insects presents a particular resemblance to the digestive apparatus of birds. First, there is a short, straight cesophagus or gullet; this expands into a much larger cavity, resembling the crop; then follows a smaller muscular part, analogous to the gizzard ; and next, a much larger and longer cavity, which is the true digestive stomach ; this becomes contracted into the intestinal canal, which sometimes runs nearly straight through the body, and in other cases is more or less con voluted ; the intestine enlarges again before it reaches the end of the body into what is known as the large intestine or colon. As in other ani mals, the alimentary canal is much longer and more capacious in the herbivorous than in the carnivorous kinds. As a rule the canal is more capacious in the larva than in the imago state. The secretory apparatus of insects, though analogous in function, is very different in appearance from that of the higher animals. Instead of solid glands, like the liver or kidney, it has the form of masses of convoluted tubes. The salivary glands, the liver, the kidneys, and the testicles are found represented in insects. The gastric and pancreatic fluids are secreted by little cells or follicles in the coats of the stomach. The muscles of insects, like those of other ani mals, consist of contractile fibres, but in their situation and attachments, as compared with those of the vertebrate animals, they are reversed; that is to say, in the latter, the muscles are situated outside of, and upon the bones, which constitute the supporting part of the body whereas in insects the supporting part is the external crust, and the muscles are attached to its internal surface. The muscles are of a pale yellowish color, and are usually presented in the form of thin layers, and sometimes of isolated fibres, and are never united into the rounded compact form which they have in the higher animals. By counting the separate fibres, a very great number of muscles have been enumerated. Lyonet counted nearly four thousand in the larva of (losses ligniperda, and Newport found an equal number in the larva of Sphinx ligustri. The muscles of insects possess a wonderful contractile power in proportion to their size. A flea can leap two hundred times its own length, and some beetles can raise more than three hundred times their own weight. This remarkable strength may probably be attributed to the abundant supply of oxygen by means of the myriad rami fications of the air tubes. Insects are evidently endowed with the ordinary senses which other animals. possess, but no special organs of sense, except those of sight, have been discovered with certainty. The eyes of insects are of two kinds, simple and compound. The simple or single eyes are called octlii, and may be compared in appearance to minute glass beads. They are usually black, but sometimes red, and are gen erally three in number, and situated in a triadIgle on the top of the bead In insects with a com plete metamorphosis, these are the only kind of eyes possessed by them in their larva state, and in these they are usually arranged in a curved line, five or six in number, on each si!'..a of the i head. We have noticed that in some insects which undergo only a partial metamorphosis, as for example the common Squash-bug (c oreus tris'is), the ocelli are wanting in the larva and pupa states, but become developed in the last or perfect stage. The compound eyes of insects present one of the most complex and beautiful mechanisms in the organic world. They are two in number, but proportionately very large, occupying in many insects nearly the whole of the sides of the head and, in the dipterous order especially, often present across their disks,bands of the richest tints of green. brown and purple. These eyes are found to be composed of a great number of lesser eyes or eyelets, in the form of elongated cones so closely compacted as to form apparently a single organ. The larger ends of these cones point outwards, and by their union form the visible eye. Their smaller extremities point inwards, toward the brain, to which they are connected by means of a large optic nerve. When'one of these eyes is examined through a strong magnifying glass, it is seen to be composed of a very great number of little facets, sometimes square, but usually six sided, each one of which represents the outer and larger extremity of one of the component parts. These facets vary greatly in number in the eyes of different kinds of insects. In the ants there are about fifty in each eye, in the Sphinx moths, about 1300; in the house fly, 4,000; in the butterfly, upwards of 17,000; and in some of the small beetles of the genus Mordelle, it is said that more than 25,000 'facets have been enumerated in one compound eye; so that if we suppose that each of these component parts possesses the power of separate vision, one of these insects must have more than 50,000 eyes. How vision is effected, or how a unity of impression can be produced by so com plex an organ, we are unable to conceive. Insects are evidently affected by loud noises, and moreover, as many insects have the power of producing voluntary sounds, it is reasonable to suppose that they possess the sense of hearing: No organ, however, which has been generally admitted to be an organ of hearing, has been discovered. It is the most common opinion of entomologists that the antennae are instrumental in receiving the impressions of sound, and that the sense of hearing is located at or near their place of attachment to the head, and this view is much strengthened by the fact that in some of the larger crustaceans, such as the lobster and crab, a distinct organ of hearing is found located at the base of the antenna. That insects are endowed with the sense of smell, is proved by the fact that the carrion-fly, and other insects which feed upon, or deposit their eggs upon, putrescent matter, detect such substances at a distance, however completely they may be hidden from the sight. The bee also' discovers honey under similar circumstances, and it is- therefore fair to presume that insects discover flowers, more by their perfume than by their visible characters. But no organ of smelling has been discovered, and' this sense is supposed, from analogy, to be located in the lining membranes of the spiracles. It is impossible to determine, but there is no reason to doubt, that insects, like other animals, taste and enjoy food of which they partake; and the manner in which they frequently touch their food, and the surfaces over which they walk, with the tips of their palpi, which, indeed, have received the common name of feelers, renders it probable that these organs are endowed with a special sense of touch The songs of birds, and the noises made by other animals, are produced by the forcible passage of air through the glottis, which is the narrow opening at the top of the wind pipe, aided by the vibration of certain muscular folds near the outlet, called the vocal chords. But we have seen that insects never breathe through their mouths, and, therefore, they never make any oral sounds. But the humming of bees and flies is produced in an analogous manner, by the expul sion of air through the thoracic spiracles, and the vibration of a delicate valve-like fold, just within the opening. But besides this, insects make a variety of noises, which are produced in different ways. The singing of the Cicada, which is the loudest noise made by any insect, is pro duced by the expulsion of air from the first abdominal spiracle, striking upon a large trans parent drum-like apparatus, situated at the base of the abdomen. The chirping of crickets is produced by rubbing together their parchment like wing covers. The well-known noise of the katydid is produced in the same way, but here the sound is intensified by a thin talc-like plate' set into the base of each wing-cover. The stridulation of grasshoppers is caused by the friction of their spined shanks across the edge of their wing covers. The fainter, squeaking sounds, made by many insects when captured, are produced simply by the rapid friction of one part of their bodies upon another; in certain Hemiptera, by the friction of the head ufron the _pro-thorax; in the Capricorn beetles, by the friction of the pro-thorax upon the mesa-thorax; and in some of the Lamellicorn beetles, by the friction of the abdomen against the wing covers. The more complex and special apparatuses of insects for the production of sounds, are pos sessed' exclusively by the males, and are supposed to be exercised by them as calls to the opposite sex; but the simpler squeaking, sounds are emitted by both sexes, and appear to be mere notes of alarm. Nothing in the history of insects is more remarkable than the striking changes of form which many or them undergo, in the course of their development Whilst other animals progress from infancy to maturity, simply by a process of growth, and by such gradual and imperceptible changes only as their growth necessitates, many insects assume totally different forms in the course of theirdevelop ment; so that they could never be recognized as the same individuals, if this development had not been actually traced from one stage to another. These changes are called the meta morphoses or transformations of insects. All insects, in their growth, pass through four stages, designated as the egg state; the larva, or caterpillar state; the pupa, or chrysalis state; and the imago, or perfect and winged state. The metamorphoses of insects are of two prin cipal kinds, complete and incomplete. In the complete metamorphosis the larva bears no resemblance to the imago, and the insect, in the intermediate or pupa state, is motionless, and takes no food. This kind of metamorphosis presents two principal varieties.. In some (Lepi doptera and many Diptera,) the legs and wings are completely inclosed in the pupa case. In others, (Coleoptera, Hymenoptera, and some others,) the legs of the pupa, though useless, are free, and the rudimental wings lie loosely upon the sides. Moreover, in some (the nocturnal Lepidoptera, and many Hymenoptera,) the pups is inclosed in a separate covering or cocoon, whereas the majority of insects have no suck covering. Pupas thus inclosed are called foil/carts The term chrysalis, from a Greek word meaning golden, is sometimes applied to the pups of the diurnal Lepidoptera, because the pups of some butterflies are ornamented with golden spots. Most insects, in changing from the larva to the pupa state, cast off the larval skin, but in many of the two-winged flies, (Muscids, SyriphidEe, etc ,) the larval skin becomes contracted and hardened, assumes an oval form, and a brown color, and thus forms a compact and closely fitting case, in which the pupa proper is inclosed, but distinct. Pupa: thus inclosed are called toarctate, and their cases are analogous to the cocoons of the Lepidoptera. In the incomplete metamorphosis, the insect presents essentially the same form, and is active iu all its stages, after leaving the egg. The pupa is distinguished from the larva by the presence of short, rudimen tal wings at the base of the alrlomen, and the imago or adult state is distinguished by the fully grown wings and wing covers. It is only in this last stage that insects are capable of pr p agation. All the Hemiptera, or bugs proper, and all the Orthoptera, or crickets, grasshoppers and cockcoaches, exhibit imperfect metamorpho sis. In treating of the development of insects, it is necessary to refer to the periodical casting of the larval skin. All the growth of insects takes place in the larva state. Consequently no insect increases in size after it has acquired wings. The larval skin seems to he an organ ized membrane which does not correspond in its growth to that of the body, but yields to this growth, to a certain extent, by virtue of its elas ticity. A. time comes, therefore, when it can yield no farther. The insect then evidently becomes oppressed, ceases to eat, usually retires to some secluded spot and, if gregarious, hud dles together with its companions, and there remains a day or two, almost motionless and without food, and in an apparently torpid and sickly condition. After a time the distended skin bursts open, and the insect throws it off, and appears in a new, bright, and elastic skin, which, in its turn, is capable of a certain degree of distension. This process, which is called moulting, takes place three or four times in the course of the larval growth, and in a few larvEe which continue More than one year in this state, the moulting is said to occur from five to eight times. In insects of very rapid development, on the other hand, such as the maggots, or larva; of lifuscidte, no moulting takes place, and it is the larvse of this kind which form coarctate pups. As a general rule insects of different sexes resem ble each other so closely as to leave no doubt of their specific identity, and in many the sexes can scarcely be distinguished. But this rule is sub ject to many exceptions, and the naming of insects has been greatly confused by the sexes of the same insect having been described and named as distinct species. The sexual organs, especially those of the males, are usually concealed so as to be nearly or quite invisible; but the female, especially in the order of Hymenoptera, often have an exserted ovipositor of greater or less length, which readily distinguishes them from the opposite sex. An analogous structure exists in many wood-boring beetles, which deposit their eggs in deep crevices in the bark of trees; and more rarely in insects of the other orders. In the Coleoptera the males are sometimes dis tinguished by one or two horns, either upon the head or thorax, and many of the predaceous beetles, both terrestrial and aquatic, have the anterior feet much widened, and furnished be neath with a cushion of hairs or bristles. The antenna; usually differ in length but little, if at all, in the two sexes; but in the long-homed beetles (CerambycidEe) the antenna; of the males are generally considerably longer than those of females. In these moths which have bi-pectinate antenna;, these parts are almost always wider in the males. Many insects in the order of Diptera are remarkable for the great size and beauty of their eyes, and these organs are almost always larger in the males, than in the females. In describing insects it is customary, for the sake of brevity, to distinguish the sexes by signs, as 3 male, 4 female. The first representing the sign Mars and the second Venus. The classification of insects depends chiefly upon the structure of the external and visible parts. It is necessary therefore that the student should have a thorough knowledge of these parts and of the names by which they are designated. But as these parte are very greatly modified in the different orders of insects,. we shall reserve a minute description of them till we come to treat of them in connec tion with the several orders respectively, and shall here give only a general enumeration of them. It often becomes necessary to refer tp different parts of an insect's bead, and they are therefore designated by particular names indica tive of their situation. These are—the Hind head, (Occiput). The Crown, (Vertex). The Fore-head, (Prone). The Face, (Fadi s). The Cheeks, ((:fence). The appendages of the head are the Horns, (Antenna); the Eyes, (Oculi); and the parts of the Mouth, ( rophi, or oral organs). All insects have two more or less elongated and usually many-jointed antenna' situated one on each side of the head, and varying greatly, in different kinds of insects, in length and in the form of their componentjoints. insects have very short antenus in their larva state, and in some perfect insects, such as the water-beetles, (Gyrini and Hydrophilz), the antenna' are not longer than the head, whilst in others, such as some of the longicorn beetles, they are more than twice as long-aTthe whole body and in some of the small moths of the genus Ailela, they are five or six times as long The uses of the antenna) are not known, but, as we have stated above, when treating of the senses of insects, they are supposed to be instrumental in the sense of hear ing. The most common variations in the forms of the antenna; are expressed by the following terms: Fikform, or thread-like; long and slender, and of the same, or nearly the same width throughout. Setiform or setaceous; or bristle-like; long and slender, but tapering toward the tip. ilioniliform, or bead-like; when the joints are about the same size, and Serrate, or saw-toothed; when each joint is some what triangular, and a little prominent and pointed on the inner side. Pectinate, or comb toothed; when the inner angles of the joints are considerably prolonged. Bi pectinate, or double comb-toothed; pectinate on both sides. Clavate, or club-shaped; gradually enlarging towards the tip. Capitate, or knobbed; when a few of the terminal joints are abruptly enlarged. Lamel late; when the joints which compose the knob are prolonged on their inner side, in the form of plates. The eyes are uniformly of a round or oval shape, and sometimes notched on their inner side, to give place for the insertion of the antennae. In a few instances they are placed at the end of foot-stalks made by a lateral prolong ation of the head. The Trophi, or parts of the mouth of insects, present two very strongly marked variations; one of which is fitted for gnawing solid substances, and is therefore called the mandibulate, or gnawing mouth; and the other is fitted for sucking fluid nutriment, and is called the haust,llate, or sectorial mouth. The mandibulate mouth is composed of six pieces, more or loss distinct, and their appen dages. First, the labrum, or upper lip; a horny, usually somewhat semi-circular plate, attached to the anterior and inferior edge of the head, and serving to close and protest the mouth in front. Theu, the Mandibles, or upper jaws; a pair of very hard, horny pieces, more or less hooked at the point, and often toothed on their inner sides, which work together laterally, somewhat like' the blades of a pair of scissors. These are the true biting, gnawing, or mastica ting organs. Next are the Maxillas, or lower jaws; a pair of organs working laterally like the mandibles', but softer and more pliable in their texture, generally divided into two lobes at their extremity, which are furnished more or less with hairs. The maxillas undoubtedly assist in the operation of eating, hut the precise part which they perform is not, well understood. Behind the maxillae is a single piece which partially closes the mouth behind, and which may therefore be considered as the counterpart of the labrum or upper lip, and is accordingly called the labium, or lower lip. In the Coleoptera this piece is usually attached at its base to the anterior face of an elevated ridge upon the under side of the head, which forms a kind of wall behind the mouth, usually deeply notched in the middle, and which is called the mentum, or chin. When the labium forms a narrow elon gated piece, diitinet from the mentum, as in most of the Coleoptera, it is now generally called the tongue, ua or lzgula. The PO43i, or appendages of the mouth, are near the base of each maxilla; and on its outer side is attached a movable ,appendage, usually composed of four or five joints, and never more than six, called the maxillary palpus; and near the base of the labium is attached a similar pair of organs, but with a less .number of joints, distinguished as the labial palpi. These appendages are subject to considerable variation especially in the shape of their terminal joints and are made much use of in determining the families and genera of insects. The haustellate, or suetorial mouth consists of a more or less elongated proboscis or sucker, which is sometimes short and fleshy, as in the flies, (Masada); sometimes more elongate, and pointed, as in the bugs, (Hemiptera); and sometimes very long and slender, and rolled up, when not in use, in a spiral coil, as in the butterflies and moths, (Lepidopt, ra). It is evi dent-that all insects with a suctorial mouth must live excusively upon liquid food, or the juices of animals and plants. The haustellum or sucker is not a single organ, as it appears, but has upon upper side a deep groove, in which are con tamed two or four, but in some of the carnivorous species (mosquitoes and,horse flies) six needle-shaped pieces, which in these last make a complicated weapon with which they pierce the skins of animals upon whose blood they subsist. From a comparison of the haustellate with the mandibulate mouth, in different kinds of insects, it has been concluded that the apparent sucker, which, as we have just seen, forms a sheath for the smaller needle shaped pieces, corresponds to the labium, and that the contained pieces must represent the mandibles and maxillae and, where six pieces are present, also the labrum and lingua. In

accordance with the proportionately great devel opment of the labium, we find that its appen dages, that is, the labial palpi, are also very prominent, whilst the maxillary palpi are very small or rudimental. This is the ease in two of the suctorial orders, the Lepidoptera and Dip tera; but the other order (Hemihtera) is excep tional in this respect, having neither maxillary nor labial palpi developed. The thorax is the second, or middle division of the bodies of insects. Though apparently single, it is really composed of three pieces which seem as though soldered together. These pieces are more distinct in some insects than in others, but they,can always he distinguished by impressed lines upon the surface called sutures. The three pieces of the thorax are distinguished as the fore-thorax, the middle thorax, and the hind thorax; or, in sci entific language, the pr o-thoroz the meso-thorax and the meta-thorax. In the Coleoptera the pro thorax is very large, and forms the large upper part or shield, to which we usually give the gen eral name of thorax. In this order of 'insects, the meta-thorax is invisible above, and the only part of the meso-thorax seen from above is the triangular piece between the bases of the elytra, called the .scutellum. In many insects (Hymen optera and Lepidoptera) the pro-thorax is much reduced in size, and forms only a narrow which is usually called the collar. The under side of the thorax is called the sternum or breast plate. Each of the three divisionS of the thorax has its sternum, designated respectively as the pro-, mesa- and meta-sternum. 1n 'many insects, and espedially the Coleoptera, each section of the sternum is divided by sutures into a middle piece sternum proper, and a side piece, episternum. The appendages of the thorax are the organs of motion, namely, the wings and the legs. The great majority of insects have four wings. 'The anterior pair are attached to the upper part of the meso-thorax, and the posterior pair to the meta-thorax. The wings are thin, membran ous, transparent organs, in some eases folded when at rest, and supported by ribs or veins run ning across them. These veins are found to cor respond in their number and complexity to the rank of the insect in the scale, and from the ease with which they can be seen, they furnish admirable characters for the purpose of classifi cation. In somo insects, such as the grasshop pers, the fore-wings are thicker and less trans parent than the hinder pair, and have nearly the consistency of parchment; and in one large order of insects, the Coleoptera or beetles, the fore-wings become converted into the hard opaque pieces known as the elytra or wing-cases. The elytra take no part in the flight, but serve only to cover and protect the hinder or true wings, which are folded under them when at rest. In one large order, the insects have hut two wings, and are named from this character Diptera, or two-winged insects. In these insects the place of the hind-wings is supplied by a pair of little knobbed appendages called halteres or poisers. There are a few exceptional cases of two winged insects in some of the other orders—for example, some of the smaller Day-flies (Ephem erce) in the order of Neuroptera, and the males of the Bark-lice (Coceicke) in the order of Hom optera. Insects have six legs, attached in pairs to the under side of eacleof the three segments of the thorax. The leg consists of four princi pal parts; the hip (eoxa), a short piece by which the leg is attached to the body; then an elonga ted piece called the thigh (femur, plural femora); then another elongated piece called the shank (tibia); and lastly the foot (or tarsus); which is composed of a number of smaller pieces or joints; of which five is the largest and most common number. The feet of insects terminate almost invariably, in a pair of sharp, horny claws (ungues); and between these, at their base, is often one or two little pads (plftatulcs) by means of which flies and many other insects adhere to glass, or any other surface which is too smooth and hard for the claws to catch upon. The Lepidoptera have but one plantula, and the Diptera have two. Besides the parts of the leg here enumerated, there is a small piece attached to the hind part of the hip. called the troehanter. This is usually small and inconspicuous, but in the hind legs of the ground-beetles (Ca rabidce) it forms a large egg-shapped appendage, which is one of the most characteristic features of this family of insects. The abdomen is the hinder most of the three divisions of an insect's body. It is sometimes attached to the thorax by the whole width of its base, in which case it is called sessile. But it is often attached by a slender petiole or foot-stalk, when it is said to be petiola tat. The abdomen is composed of a number of rings, one behind another, each ring Usually lap ping a little upon the one following it. The normal number of rings or segments of the abdomen is considered to be nine, and this num ber is actually present in the earwig (Foiftca/u) and a few other insects; but in the great ity of insects, several of the terminal segments are abortive, and only from five to seven can usually be counted. In the females of many kinds of insects the abdomen terminates in a tubular, tail-like process, through which the eggs are conducted to their place of deposit, and which is therefore called the ovipositor. In some insects the ovipositor is simple, short, straight and stiff, as in some of the Capricorn beetles; but in others, as the Iehneumon flies, it is long, slender and flexible, and composed of three thread-like pieces, which when not in use, are separated from each other,' giving these insects the appearance of being three-tailed. Insects which do not readily fly, such as the bee tles and the bugs proper can be captured with ' the fingers, and are most easily killed and also preserved, for the time being, by dropping them into alcohol. For this purpose every collector should have in his pocket one or more small, strong, wide-mouthed bottles, sectirely corked, and filled about two-thirds full. with alcohol. The common 'morphine bo1les answer this purpose very well. The quinine bottle can be used when a larger bottle is required. The insects can be left in the alcohol till the col lector has leisure to pin them. They can be taken from the bottle with a pair of forceps, or the alcohol can be turned off into another bottle, and the insects shaken out on to a newspaper, or blot ting paper, which quickly absorbs the moisture. Insects which readily take flight, must he cap tured in a net, which is made like a small dip net for fishes, by making a hoop of stout wire about ten inches in diameter, with the ends of the wire turned out so as to form a short handle three or four inches long, and this can be length ened by inserting the ends of the wire into a wooden handle about two feet long. The net is made of lace or tarlatan muslin, twenty inches or more in depth. Many species otherwise seldom seen, can be obtained by beating the branches of trees, especially forest trees, and catching the insects as they fall. A common umbrella, inverted' under the tree, answers this purpose very well. This is in many ways a very useful imple ment to the collector. It will serve to protect him from the direct rays of the sun, or from a casual shower; and the hook at the end of the handle will enable him to di aw down branches so that they can be satisfactorily examined. The umbrella would be improved by being covered with white cloth, upon which small insects would be more easily detected. Most insects except those above mentioned are injured by being im mersed in alcohol, and butterflies and moths would be ruined by it. These insects can be killed by wetting them with benzine or chloro form. The benzine is the cheaper, and the only objection to it is its disagreeable odor. Large insects require to be saturated with chloroform several times to destroy life. A very neat way to kill the smaller moths is to put them under a wineglass and put in with them a tuft of wool sat urated with chloroform. The moths are killed by the fumes, without being wet or handled. Some use for this purpose a poisonous preparation called cyanide of potassium. In mounting bee tles the pin should be passed through the right 'wing-cover; other insects are pinned through the thorax The pin should be inserted so far that half of it will project below the body of the insect. The value of a collection of insects is greatly enhanced by having the legs and wings of the specimens displayed in a life-like attitude. For this purpose they must be set out with pins, and held so a day or two till they have become fixed. For spreading the wings of butterflies and moths it is indispensable to have a simple apparatus called the stretcher. It consists of two strips of nicely dressed soft pine wood, eighteen or twenty inches long, two inches wide, and about three-eighths of an inch thick, placed side by side half an inch apart at one end and a quarter of an inch at the other, so as to accommodate insects of different sizes, and held so by a sleet across each end. The space between the strips must be closed on the underside by pieces of sheet cork tacked to the board. The space between the strips is to receive the of the insect, the pin being passed through the cork so as to bring the wings on a level with the upper side of the stretcher. The wings are spread by catching them just be hind the stout front rib with a pin, or, what is better,. a needle set into a little handle, and car rying them forward, till the hind margins of the fore-wings are on a straight line with each other. They can he held in this position either by strips of card laid across them and fastened with pins, or by inserting a single small pin through the wing, behind the rib, and into the side pieces of the stretcher, which on this account should be be made of the softest kind of wood. For very small moths the stretcher must be constructed upon a smaller scale. Insects must be allowed to dry thoroughly before inclosing them in the cabinet. Beetles which have been permitted to dry with their limbs contracted, can be relaxed by putting them into hot water.' Boxes for the permanent preservation of insects may be seven teen or eighteen inches square, two and a half inches deeP, outside measure, and one inch and a half or a trifle more in the clear, made of perfectly seasoned wood, halved together in the middle, so as to have an upper and lower part, the former serving as the cover. The lower part must be lined on the bottom with sheet cork or thin strips of corn-stalk, and the whole covered with soft white paper. The paste with which the paper is attached should have a portion of arsenic stirred in with it, to guard against destruc tive vermin. The upper part, or cover, should be cut in around the top, like a window sash, so as to receive a piece of glasa, which ia to be secured in the usual way with putty. Every in aect drawer should have a lump of gum camphor rolled in a piece of muslin and pinned into one corner, to keep out destructive vermin.- The presence of vermin ia detected by little heaps of the dust-like gnawings under the infested speci mens. Such specimens should be at once re moved, and if the drawer is much infested, a teaspoonful or two of benzine should be poured upon the bottom, and the drawer or box imme diately cloaed, ,ao as to retain the fumes. A magnifying glass consisting of one, or, what is better, two lensea, so arranged that they can be used either singly or combined, is absolutely indispensable instudying insects. A common mis take is to suppose that insects can not be studied and classified without the use of a complex and costly microscope. Such instruments are useful only to examine excessively minute or transpar ent objects, and though sometimes indispensable to the professional entomologist, they are rarely used in the ordinary study of insects. Instinct is that faculty by which animals are enabled to discover their food, construct their nests, and provide for their young, and to perform these operations without having had any previous education or experience. Many of the manifes tations of this faculty are truly wonderful and unaccountable. , Such are the mathematically accurate construction of the cells of the honey comb; the curious economy of the ants and bees; and the provisions which many kinds of insects make for the future subsistence of their young, even in advance of their existence. Instinct is often spoken of as an imperfect or partially developed reason, but its relation to that faculty can be, at most, only that of a very remote analogy. It differs from reason in its invariable ness and its almost absolute infallibility, but most essentially in its independency of previous knowledge and experience. Reason acts only by virtue of what is already known, and man, who vastly excels all other animals in his reasoning powers, approaches perfection in any complex work only by long study and practice; the honey bee, on the contrary, constructs its first cell with such mathematical accuracy that it cannot be improved by any subsequent experience. Some of the higher animals, such as the horse and the dog, give proof of the possession of a reasoning faculty similar to our own, and inferior only in degree. But whilst the manifestations of reason are fainter as we descend in the animal scale, instinct becomes more remarkable, and in insects / especially, in which reason is almost if not abso lutely wanting, inatinct is exhibited in its highest perfection, far aurpassing, in many instances, in accuracy and prescience, the reason of man him self. Of the nature of the instinct of animals, as of that of the human mind, we know absolutely nothing; and we can only confess our ignorance by referring ita wonderful manifestations to the direct agency of the Creator. In regarding insects from a practical or economic point of view, we have to consider them in both their beneficial and their injurious relations. The directly beneficial insects are almost limited to the three well-known species: the honey-bee, the silk-worm and the cochineal-insect; whereas, those species which are injurious to mankind, chiefly by depredating upon valuable cultivated crops, are much more numerous, although con stituting but a very small proportion of the whole insect world. It is important to bear in mind that in these destructive operations insects occupy an exceptional or abnormal position, and' that we ourselves have been the means of bringing about this state of things, by the excessive culti vation of certain plants, whereby' a correspond ing increase of certain species of the insects which feed upon them has been induced. It is very rarely that any such loss of balance between the insect and the vegetable worlds takes place in the state of nature; and yet, such occurrences are not wholly unknown. This has happened most remarkably in the case of wood-eating insects, there being instances on record in which extenaive tracts of forest trees have been destroyed by the larvae of some of the more minute wood boring beetles. But, as just stated, it is in their depredations upon some one or other of the more valuable cultivated crops that insects have come into the most direct and serious conflict with human interest. These depredations, as is well known, have often been of a most extensive and ruinous character, causing the annual loss of crops to the value of many millions of dollars, and in some seasons and localities, necessitating the total abandonment of some of the most valu able and staple productions, such as wheat, barley and potatoes, and also some of our choicest fruita, such as the plum and the peach; and sometimes threatening the destruction even of the most valuable fruit of all—the hardy and widely distributed apple. These destructive operations of insects have necessarily attracted to them the most earnest attention of both prac tical and scientific men, and many valuable treatises and have been written which have been devoted chiefly to the practical treat mentnf the subject. It is our present intention to treat of insects from a more general and comprehensive point of view. From what has just been said, it is evident that it is in the nature of their food and their food-taking habits, that insects hold the closest relationship to human interests; and this is true not only in the direct manner above described, but also indirectly, by means of the important parts which they fulfil in the economy of nature. Indeed, the opera tions of insects in this last respect are of such vast importance, that it would be safe to say that if these should cease, the earth would soon become uninhabitable by mankind, These operations consist chiefly, first, in the destruction of other insects by predaceous and parasitic kinds, holding in check excessive increase; second, i in the instrumentality of a large proportion of insects in their character of scavengers, whereby the decomposition of decayed and offensive mat ters, both animal and vegetable,-is effected and accelerated; and third, in the agency of insects in causing the fertilization of plants, especially those with very deep corrollas, and those which have the-barren and productive flowers upon dif ferent plants, by carrying upon their legs, in their search for honey, the fertilizing pollen from one flower to another. A long chapter might be writ ten upon each of these topics, but we have space her barely to enumerate them. In the division of insects according to the nature of their food, i all may be divided into two classes—the carniv orous insects, or those which eat animal food (Sarcaphaga); and the herbivorous insects, or those which subsist upon vegetable substances (Phytophaga). Each of these classes is again divisible accordingly as the insects which com pcs:3 it take their food in a fresh and living state, or in a state decay. The former are called pre daceous insects (Adephaga) when they live upon animal prey; and the latter are designated by the name of scavengers (Rypophaga). Those insects which eat living animal food, are still further divisible into predaceous insects proper, which seize and devour their prey, and parasitic insects, which live within the bodies of their victims and feed upon their substance. Those insects which feed upon decaying animal matter present three divisions: first, general scavengers, which devour particles of putrescent matter wherever they may be found; second, those which live exclusively in or upon the bodies of dead animals (Necrophaga); and thirdly, those which are found exclusively in animal excrement (Coprophaga). The herbiv orous insects may be divided in a similar man ner into those which eat fresh vegetable food aikalerophaga) dud those which subsist upon 'hitegetable matters in a state of decay (Saprophaga). They can also be usefully classified according to the particular parts of the plant which they devour, into lignivorous or wood-eating insects (Xylophaga); the folivorous, or leaf-eating insects (Phyllophaga), and the fruetivorous or fruit-eating insect (Carpopha,ga). The above Greek terms in parenthesis have been used chiefly in connection with insects of the Coleopterous order, in which these diversities of food-habits exist to a much greater extent than in any of the other orders, but the terms themselves are of general significa tion, and being very concise and comprehensive, they might, not improperly, be used in speaking of insects in all the orders, so far as they are applicable. In attempting to classify insects according to the nature of their food we meet with a peculiar difficulty, owing to the remarkable change which some species undergo in this respect in passing from the larva to the perfect state. Most caterpillars, for example, feed upon leaves, whilst the butterflies and moths which they pro duce subsist upon the honey of flowers, or other liquid substances. Some two-winged flies (Asada) feed upon the roots of plants in their larva state, but become eminently predaceous in their winged state. Another remarkable example is furnished by certain coleopterous insects (Metoicke), which are parasitic in their larva state, but subsist upon foliage after they have assumed the beetle form. The question therefore arises, to which stage of insect's nsect's existence shall the precedence be given in this respect? At first view it would seem that the perfect state ought to govern, but when we take into account that insects are com paratively short-lived in this state; that having arrived at maturity they require but little food; and that some insects take no food at all at this stage of their lives; whereas all the growth of an Insect takes place whilst it is in the larva state, and consequently it is in this state that they feed so voraciously; when we consider this, it seems more reasonable that in classifying insects upon this basis, the food habits of the larva should take the precedence. The terms noxious and injurious re often used indiscriminately, but strictly speak ing, noxious insects are those which are endowed with some poisonous or otherwise hurtful quality; and these are divisible into two classes accord ingly as they are hurtful to mankind directly, such as the mosquito, flea, and bed-bug; or are hurt ful to the domesticated animals, as the horse-fly, the bot-fly, and the various kinds of animal lice. The insects which attack man directly are annoy ing rather than seriously hurtful, and this is usually the case also with those which molest the domesticated animals; but these sometimes mul tiply so as to seriously impoverish the animals which they infest. The term injurious, as dis tinguished from noxious, is properly applied to all those insects which damage mankind indi rectly, but often to a most serious extent. by depredating upon those crops, cultivated, upon which we depend for subsistence and profit. 'It is worthy of remark that by far the greater proportion of the damage caused by injurious insects is effected by species of very small size, whilst the large species are generally harmless. The two most serious fruit insects, the Codling moth and the Plum-curculio, are both below the medium size, and the Apple bark-louse, the Apple-aphis, the Hessian-fly, and the Wheat midge, arc so minute that they would not be noticeable were it not for the wide destruction which they cause to some of our most valuable crops, in consequence of their excessive multi plication. It is also an important consideration that in learning the elements of any science or art, an indispensable, part of such education is to acquire a knowledge of the more common tech nical /terms which properly belong to it, and which constitute its peculiar phraseology, and which the student will continually meet with in all wkitings upon the subject. The forms with which it has to deal are so numerous and diversified, and often, at the same time, so closely allied, that their classification constantly demands a minute and careful examination, and a discriminative analysis, which, regarded purely as an exercise of the mind, are scarcely inferior to those required by the abstract mathematics, whilst they possess the additional interest which n atu rally attaches to the study of living beings. Classification in natural history has two objects in view—first, to show the relationship which exists between organized beings, by putting them in ,groups, in accordance with the similarity of their characters; and secondly, to facilitate the study of them by enabling the student to com prehend a great number of different but allied forms under a comparatively small number of general heads, and thus to afford an important aid to the memory. By nomenclature is meant the giving to these groups and the species which compose them distinctive names. It is the' natural tendency of the specialist to attach undue value to the minor subdivisions of his par ticular department, whilst he whose studies take a wider range sees more forcibly the necessity of condensation and simplification. Much can be said upon both sides of this question, but perhaps the argument may be condensed into a single sentence by saying that, on the one hand, the minute subdivision of a natural group tends to give definiteness and precision to our in vestigations, whilst, on the other hand, the multiplication of genera or sub-genera, upon trivial characters, unnecessarily encumbers our nomenclature, and 'diminishes the interest and importance which ought to attach to the generic distinction. the names of insects— and the same rule applies to all other depart ments of natural history—it is the established custom to write first the name of the genus, usually without the author's name attached, and immediately following it the specific name, with the name of the original describer, or an abbre viation of it appended. As no one can carry all the modern genera of insects in his memory, it is an excellent practice, when space permits, to prefix the name of older and more compre by examples: The common rose-slug is the larva of a little wasp-like insect, known scientifically as the Selandria rola of Harris. This species was first described by Dr. Harris, who gave to it the specific name ram, meaning of the rose. It belongs to the modern genus Selandria, which was founded byDr. Leach, an English entomolo gist. This genus is a subdivision of the old genus Tenthr•edo, of Linnfeus. The name written in full, therefore, will stand: Tenthredo (Selan arna, Leach) TOSCO, Harris. Our tine large Polyphemus moth was originally de scribed by Linnaeus under the name of Attaeus Polyphemus. It belongs to the modern genus Telea, made by the Ger man lepidopterist, Its name, therefore, expressed in the simplest man ner, is 1 dea Pokplienrus, Linn. ; or writ- r ten in full —.Aigacus (Telea; Hubner) Polyphemus, Linnaeus. This is ordi narily all that is essential to be known, and any additional synonyms or refer ences should be placed in a subordinate T. 11 is 11 post Iti 11. wi observed no the family names of insects end in idol This is a Greek termination, meaning like or similar, and implies that all the species in any such group have a family resemblance to those of the leading genus to which it is affixed. —thus:' Cieindeticke means Cieincielcalke in sects. In pronouncing these words the accent is placed upon the syllable preceding this termina tion, thus: Cieindel-idce, Carab-idce, etc. It is often the case that families,- especially those which contain many species, admit of division hensive genus to which such species was formerly referred, and with which most entomologists may be presumed to be familiar. In this case the modern genus is included in a parenthesis,, and usually the author's name attached. To illustrate into a number of natural groups of a higherrank than genera, which are designated as sub-families, and distinguished by the termination ides.. .Thus the family Carabithe is divided into a number of sub-families, such as the the Searit ides, etc. . The class of insects is divided into a number of primary groups called orders. Be tween these' larger divisions are certain smaller ones, which serve as connecting links between them, and which some authors have merged in one or the other of the adjoining larger groups,. whilst others have considered them of sufficient importance to be raised to the same rank with the larger ones. From this it has resulted that the number of orders into which the class of insects has been divided has varied, even in- the works of standard authors, from seven to twelve, and the number will he still inorcased if we regard as distinct orders certain apterous form, such as the lice (Pedicult), and the spring-tails (Thysanoura). But as in such an article as the present one the classification of insects should be simplified as much as possible, we have adopted the smaller the investigations of more recent authors. As illustrating some of the principal forms of insect life, we show a variety of forms, all injurious except one, the Spotted Ladybird.