COLEOPTERA, or Beetles, a vast and remarkably homogeneous order of Insects, characterized, as the name implies (κoλ∈o ’ s, a sheath, and τrτepα, wings), by the structure of the upper wings, or elytra, as they are called, which are so modified as to form shields for the protection of the under wings—the true organs of flight in those insects. The name was given, and the principal characters of the order defined, by Aristotle; and owing doubtless to their singular and varied forms and habits, the brilliant colouring and great size of numerous species, and that solid consistence which renders their collection and preservation comparatively easy, Coleopterous insects have since the days of the Stagirite received the special attention of entomologists.
The body in Coleoptera is enclosed in a chitinous integument of a more or less rigid consistence, and is somewhat oval in form, although in most cases greatly longer than broad. In this respect, however, the utmost diversity prevails even among the members of the same family, the form being modified to suit the habits of the insect. Thus, according to Bates, among the South American forms of Dermestidae, the species of one group are cubical in shape, and live in dung; those of another, inhabiting the stems of palm trees, are much flatter; those of a third, only found under the bark of trees, are excessively depressed, some species being literally “as thin as a wafer;” while the members of a fourth group of the same family are cylindrical in shape, and are woodborers, “looking,” says Bates, “like animated gimlets, their pointed heads being fixed in the wood, while their glossy bodies work rapidly round so as to create little streams of saw-dust from the holes” (Naturalist on the Amazons). The body, in common with that of all other insects, is divided into three parts,—head, thorax, and abdomen. The head, which is usually rounded or somewhat triangular in shape (except in the Weevil tribe, where it is produced into an elongated rostrum or snout), bears the organs of the senses. The eyes of beetles are two in number and compound, and in predaceous species are somewhat protuberant, thus affording greater range of vision. The simple eyes, or ocelli, common among butterflies and moths, are almost unknown among beetles, although present in the larvae. In many species, especially of Lamellicorn Beetles, these organs are more or less completely divided by a process known as the cantfius; and in the Gyrinidae, or Whirligigs, the intersection is so complete as to give the appearance of a pair of eyes on each side. In burrowing and cave-dwelling species, whose lives are spent in almost total darkness, the eyes, although distinctly visible in the young, become more or less atrophied in the adult forms. The two antennae, supposed by some to be organs of hearing, and by others of smell, are placed between or in front of the eyes, and usually consist of 11 joints. These differ greatly in form and size, not only in different species, but in the two sexes of the same species, the most prevalent forms being the setaceous, moniliform, serrate, pectinate, clavate, and lamellate. In many groups the antennae are exceedingly short, while in such forms as the Longicorn Beetles they, in a few cases, measure four times the length of the body.
The parts which go to form the mouth are typically developed in beetles, and for this among other reasons the order Coleoptera has generally been placed at the head of the class of insects. It is known as the masticatory mouth, and consists of the four parts (Plate VI. fig- 1). (1) The labrum, or upper lip, is usually a continuation of the upper surface of the head. (2) The mandibles, or true masticatory organs, consist of two powerful arched jaws generally dentated, moving horizontally and opposed to each other, the teeth in some cases interlocking, in others, as in the Tiger Beetles, crossing like the blades in a pair of scissors. In many species they are so small as to be almost concealed within the cavity of the mouth, while in such forms as the Stag Beetles they measure half the length of the entire body. The form and texture of the mandibles are largely dependent on the nature of the insect’s food, being acute and sharply dentated in predaceous species, and thick and blunt in vegetable feeders. Their margins are soft and flexible in those which feed on decaying animal and vegetable matters, while the entire mandibles are soft and flattened in those which live on fluids. (3) The maxillae, or lesser jaws, placed beneath the mandibles, and like them moving horizontally, serve to hold the food and guide it to the mouth. Their extremities are in many cases furnished with a movable claw, and their inner surfaces with a series of bristles, which are probably of use in straining the juices from their food. The maxillae are provided with a pair of appendages called maxillary palps—delicate organs that vibrate intensely, and are supposed to be principal organs of touch. (4) Tlιe labium, or lower lip, also provided with palps.
The thorax bears the organs of locomotion, consisting of three pairs of legs and two pairs of wings (Plate VI. fig. 2). The legs vary in their structure and development according to the habits of the species; thus in running and walking beetles these organs are usually of equal length, and generally similar in other respects, the anterior pair, however, being often stronger in the male than in the female; and in a few species, as the Harlequin Beetle, the anterior legs are enormously elongated and proportionately thickened. In burrowing beetles the anterior legs are developed into fossorial organs with broad and strongly dentated tarsi, and in arboreal forms the under side of the tarsi is usually covered with hair, forming a cushion-like sole terminating in toothed claws, by which they are enabled to keep their footing on the leaves and branches of trees. Water beetles generally have the posterior pair of legs elongated, flattened, and ciliated, so as to form swimming organs; those known as Whirligigs using the middle and posterior pairs for this purpose, while the anterior limbs are employed as rudders; and jumping beetles, as Halticidae, have the thighs of the posterior pair of legs greatly thickened for saltatory purposes (Plate VIII. fig. 10). The two anterior wings become solidified in beetles, and are thus rendered useless as organs of flight. They are termed elytra (eλυτpov, a shield), and serve to protect the delicate wings beneath, as well as the stigmata, or breathing pores, placed ¾loug the sides of the abdomen. The elytra are always present except in the females of a few species, as the Glow-worm, and are generally large enough to cover the upper surface of the abdomen and to conceal the under wings when at rest. In Brachelytrυus Beetles, however, they are exceedingly short, and the wings in these are only shielded by being folded more than once beneath them. The elytra when at rest meet on the middle of the back, their internal margins forming a straight longitudinal line or suture highly characteristic of the Coleoptera; but even this character is not universal, as in the Oil Beetles (Meloë) and a few others the one elytron partly folds over the other. The posterior wings are large, veined, and membranaceous and form the true organs of flight, but they are much more frequently absent than the elytra, and where this occurs, as in manyCarabideous Beetles, the latter are more or less soldered together. During flight the elytra are either extended horizontally or merely raised without being separated, as in the Rose-Chafers (Cetonia); and as might be expected from their general stoutness of body and comparative deficiency of wings, the flight of beetles is heavy and seldom long sustained. Their weakness in this respect is further shown in the apparent inability of many species suddenly to alter their course so as to avoid collision with any object that may unexpectedly come in their way, a defect popularly but erroneously attributed, in. the phrase “as blind as a beetle,” to weakness of sight rather than of wing. In certain water beetles fDytiscidae) a pair of aslulae, or winglets, are developed at the inner angle of the elytra.
The colouring of the chitinous integument of beetles is often exceedingly brilliant, and the elytra and other parts of many species are largely used in the manufacture of personal ornaments. This colouring can in many instances be shown to bear a close resemblance to that of surrounding nature; thus burrowing beetles, and those which dwell in subterranean .caves, are generally black or brown; "Weevils, found on the ground, are earth-coloured; while arboreal species of this and other groups are of various shades of green. Bates found a species of beetle, on a particular tree in South America, which so resembled the bark on which it spent its existence as to be, when motionless, no longer visible. This assimilation in colour to surrounding nature is probably useful in assisting them to elude their enemies; and when the markings are such as to render the beetle conspicuous it is often provided with, and no doubt protected by, an offensive odour or nauseous juices; thus the naturalist already mentioned found on a sandy beach two species of Tiger Beetles, the one of a pallid hue like the sand it ran upon, the other of a brilliant and conspicuous copper colour, but having “a strong, offensive, putrid, and musky odour,” from which the other was entirely free. Fireflies, a group of Coleopterous insects, are also exceedingly conspicuous, but are similarly protected. The phenomena of mimicry, or the imitation of one animal by another for protective purposes, have been, observed in several instances among beetles. Mr Belt, in his interesting work, The Naturalist in Nicaragua, states that he captured what he supposed was a hairy caterpillar, but on closer inspection he found it to be a Longicorn Beetle, the antennae being concealed among the hair. Hairy caterpillars are almost universally rejected by insecteating animals, and thus probably this beetle shared in the immunity from attack accorded to its model. A species of beetle found in South America closely resembles a bee found in the same locality, its body being covered with hair and its legs similarly tufted; another, with yellow banded abdomen, sufficiently resembled a wasp as to make its captor both cautious and. timid in handling it at first. One of the Chrysomfilidae (Crioceris merdigera} is said to disguise itself by covering its upper surface with its own dung; while many species to be afterwards noticed, when in danger, simulate death. Brilliant colouring in beetles is not as in some orders of animals a characteristic mainly of the male sex, both sexes being usually similar in this respect, while iu those cases in which they differ, the female is generally the more gaudy insect. The chief external difference, however, between the sexes in many beetles is to be found in the presence of horns on the head and thorax of the males. These vary exceedingly in their development even in individuals of the same species, while in their form they resemble the horns of the rhinoceros, and the antlers of the stag; and as among mammals the reindeer is exceptional in the possession of antlers by both sexes, so among beetles there is at least one species, Phanaeus lancifor, in which both male and female are similarly equipped. The male beetle has not been observed to use its horns either for purposes of offence or defence, some of the most pugnacious species being entirely destitute of them; and in Darwin’s opinion these appendages have been acquired merely as ornaments.
The abdomen of Coleopterous insects is sessile, that is, attached to the‘thorax by its largest transverse diameter. On the under side it is always of a firm horny consistence, while the upper surface is generally soft, being protected by the elytra and wings; when these, however, are absent or abbreviated, it is as hard above as below. It bears the organs of generation as well as the respiratory openings, or stigmata, which form the apertures of the tracheae by means of which air is disseminated through all parts of the insect system. Beetles belonging to several distinct families possess stridulating organs, and these are generally found in both sexes. The apparatus by which the sound, loud enough to be heard in many cases at some yards distance, is produced, consists of a couple of delicate rasps placed on the upper surface of the abdomen, on the elytra, or on the prothorax, and a scraper formed by the margins of the elytra, the edges of the abdominal segments, or the mesothorax, the rapid motion of the latter over the rasps producing the sound. In many cases, according to Darwin, the males only stridulate, the females being destitute of those organs, and in such cases the sound is employed as a call to the female; with most beetles, however, the stridulation proceeds from both sexes and serves as a mutual call. Beetles are entirely destitute of stinging organs, but a few are furnished with a retractile tube, or ovipositor, at the extremity of the abdomen, by means of which they deposit their eggs in the cracks of wood and other suitable localities.
The eggs of beetles are deposited in a great variety of situations, and in the case of a certain group of Staphylinidae found in the nests of white ants in South America, it was recently discovered by Schödte that the eggs are not deposited at all, but remain in the abdomen until they are hatched. These ovo-viviparous beetles are only one-tenth of an inch in length, and have the abdominal region enormously distended and turned over so as to rest on the back. Dung beetles deposit their eggs in the midst of the manure on which the future larvae feed; the Sacred Beetle of Egypt rolling each of hers about until a globular pellet is formed, when the whole is buried in the ground; while the Sexton Beetle finds an appropriate nidus for her eggs in the dead bodies of animals. One species of Cleridae selects the nest of the solitary bee, another (Plate VII. fig. 31) that of the hive bee, while several species of Rose Beetles choose the nest of the ant for this purpose. The water beetles belonging to the genus Hydrophilus deposit their eggs in a single mass, which they surround with a oocoon, formed of a silky substance secreted by certain glands in the abdomen, and then either fix this to the leaf of an aquatic plant or leave it to float on the surface of the water. Certain species of the Weevil tribe deposit their eggs on the leaves of trees, splitting the median nervures in several places, and afterwards rolling them up. In its progress from the egg to the perfect insect the beetle undergoes complete metamorphosis, passing from the larval to the pupa stage, and remaining totally quiescent during the latter. Coleopterous larvae generally consist of 13 segments, of which those forming the head and thorax are usually of a hard horny texture,—the mouth, as in the perfect insect, being masticatory, and the eyes, when present, simple, or ocelli. They have usually six legs, and prolegs, as in caterpillars, are occasionally present; but the larvae of many species are legless grubs, while in others the limbs are but feebly developed. In those groups in which the elytra are abbreviated, the larvae are exceedingly active and closely resemble the perfect insect. Like their parents the larvae of beetles feed on living animals, on plants, or on decaying animal and vegetable substances, but greatly exceed the perfect insect in the quantity of food which they consume, and it is in this condition that beetles do most injury to field crops and forest trees. The larvae of burrowing beetles, known as “White Worms,” spend their existence in the earth, and are destitute of eyes; those of the Stag Beetles and other wood-boring groups live in the trunks of decaying trees; mealworms—the larvae of Tenebrio molitor — live enveloped in flour, and those of the Corn Weevil in the heart of the wheat grain; while those of another species of Weevil make their homes in the fleshy parts of the receptacles of composite flowers. The larvae of Oil Beetles (Melo'e), or at least certain species of them whose life-history has been observed, after leaving the egg, which the perfect insect has deposited just beneath the surface of the ground, climb upon the stems of plants, and take the first opportunity of attaching themselves to any insect that may happen to alight near them, and in this way they are occasionally conveyed into the hives of bees, in which alone they meet with their appropriate food. Only a few of them are thus fortunate, the majority of the larvae getting attached to the wrong insect, and so perishing of hunger. The species probably owes its preservation to the great number of eggs, amounting to upwards of 4000, deposited by a single female. The larvae of one group of water beetles, Hydrophilus, swim readily by means of their ciliated legs, those of another group, Dytiscus, make use also of their flexible abdomen provided at its extremity with a pair of leaf-like appendages (Plate VII. fig. 6); while the Whirligig larvae (Gyrinus), in addition to ciliated swimming organs, are provided with four movable hooks on the posterior segment, by which they are enabled to take extensive leaps (Plate VII. fig. 17). The duration of the larval state varies in different groups of beetles, being comparatively short in leaf-eating species, but lasting for three or four years in those which burrow in the earth or in wood. The larvae in the latter case pass the winter in a torpid state, abstaining almost entirely from food, until awakened from their temporary trance by the return of genial weather, when they greedily attack their favourite food, and grow rapidly. In passing from the condition of a larva, the beetle does not, like the butterfly, assume a form altogether different from that of the perfect insect, but in the pupa or nymph state shows all the parts of the future insect, only in a condition of almost complete immobility. In preparing for this quiescent period, the larvae of many species surround themselves with a cocoon, consisting, in the case of the Scarabaeidae, of earth and small pieces of wood glued together with saliva, and in that of the Goliath Beetles, of mud. Others resemble the larvae of moths in constructing tubes in which to undergo their transformations, while the Jarvae of Lady-Birds— Coccinella— suspend themselves by the tail and make use of their larval covering as a protection to the nymph within. When the condition of nymph is assumed in autumn, no further change takes place till the ensuing spring, but under suitable conditions of heat this stage does not last usually for more than three or four weeks, after which it emerges a full-blown beetle.
The number of known species of beetles is estimated at J0,000, and these are probably not more than one-half of the total number in existence—Great Britain alone possessing 3614 indigenous species. They occur in greatest abundance in the wooded parts of tropical regions. “A large proportion of the beetles of the tropics,” says Wallace, “are more or less dependent on vegetation and particularly on timber, bark, and leaves in various stages of decay. In the untouched virgin forest the beetles are found at spots where trees have fallen through decay and old age.” The number gradually decreases towards the poles, only a few species occurring as far north as Greenland. The six zoological provinces proposed by Mr Sclater in 1859 as applicable to the existing distribution of birds, have lately been shown by Mr A. R. Wallace, in his admirable work on the Geographical Distribution of Animals (1876), to mark off equally characteristic groups of Coleopterous insects, a conclusion arrived at from a study of the distribution of the following six important families :— [table]
The Palaearctic Region, which comprises Europe, Africa north of the Sahara, and Northern Asia, possesses about 20,000 species of beetles, and is specially characterized by abundance of Carabidae, nearly two-fifths of the entire number belonging to this region; Longicorns are also well represented by 196 genera, of which 51 are peculiar to it. The Coleoptera of the Canary Islands, Madeira, and the Azores are Palaearctic, but are peculiar in the total absence of such forms as the Tiger Beetles, the Chafers, and the Rose-Chafers, also in the great number of wingless species. The latter are specially numerous in groups of beetles peculiar to those islands, but they also occur in other cases, 22 genera which either usually or at least sometimes are winged in Southern Europe having only wingless species in Madeira, while at least three species winged in Europe occur in those islands in an apterous condition. On the other hand, those species in Madeira which possess wings have them more largely developed than they are among allied continental forms; the strong-winged and the wingless thus appearing best suited to live in islands exposed, as these Atlantic groups are, to frequent storms. The Ethiopian Region, which includes Africa south of the Sahara and Madagascar, is specially rich in Cetoniidce, possessing 76, or more than half of the known genera, with 64 of these peculiar to it, of which no less than 21 are found exclusively in Madagascar. It has also 262 genera oí Longicorns, 216 of which are peculiar. The Oriental Region, comprising Southern Asia and the islands adjacent, contains some of the most remarkable forms of Carabidae, as Mormolyce phyllodes, and is rich in gorgeous metallic beetles (Buprestidae) and in Longicorns, having 360 genera of the latter, with 70 per cent, peculiar to it. The Australian Region shows affinity with the Oriental in its Coleoptera; it is equally rich in peculiar forms of Longicorns, and is the richest of all the regions in Buprestidae, having 47, or more than one-half of the knowm genera, and 20 of these confined to it. Several genera belonging to this and other families have their species divided between the Australian and Neotropical or South American Regions, and this resemblance has given rise to the supposition that at some distant period a land connection existed between the two continents; it is more probable, however, as Wallace holds, “that it may have arisen from intercommunication during the warm southern period -when floating timber would occasionally transmit a few larvae from island to island across the Antarctic seas.” The Neotropical Region comprehends southern and Central America and the West Indies, and is enormously rich in Longicorn Beetles, having no fewer than 516 genera, of which 487 are found nowhere else. The most remarkable fact in the distribution of the Stag Beetles (Lucanidae) is their almost total absence from the tropical parts of this region, and their presence in North America, while in the old world they are specially characteristic of the hottest parts of the Oriental and Australian Regions. The Nearctic Region comprises the northern and temperate parts of America, and is comparatively poor in Coleoptera, showing greater affinity, however, with the Palaearctic than with the contiguous Neotropical Region.
The insects belonging to this extensive Order comprise numerous well-defined and generally recognized families, but great diversity of opinion exists as to the best mode of grouping these together so as to exhibit their natural affinities. Geoffroy, a French naturalist, was the first to make use of the number of joints in the tarsi for this purpose, a method adopted and extended by Olivier, and brought into general use by Latreille. According to the tarsal system the Coleoptera are divided into the following four sections :—(1) Pentamera, in which all the tarsi are five-jointed; (2) Heteromera, with five articulations to the first four tarsi and four to the posterior pair; (3) Tetramera, with four articulations to all the tarsi; and (4) Trimera, with all the tarsi three-jointed. Macleay, an English naturalist, altogether rejected the tarsal system of Geoffroy, and founded his five primary divisions on characters derived from the larvae of those insects—a system adopted by Stephens in his Classification of British Insects, and by several other English writers on this subject. The tarsal system is to a large extent artificial, and when slavishly followed brings together forms which in other respects differ very widely, while separating many that are as obviously related. Its simplicity and consequent easiness of application have, in the absence of a more natural system, led to its very general adoption by both British and foreign naturalists, who do not, however, apply it where obviously unnatural.
Pentamera. —The majority of the beetles in this section have the tarsi of the feet five-jointed, and they comprise fully one-half of all the known species of Coleoptera. It is subdivided into the following 8 groups :—
I. Geodephaga, or Predaceous Land Beetles, resemble the succeeding group and differ from other Coleoptera in having the outer lobe of the maxillae distinct and articulated, thus appearing to possess six palpi. They are extremely active, their legs being admirably adapted for running; the majority are nocturnal in their habits, secreting themselves under stones and clods of earth; and all are carnivorous, feeding on other insects and occasionally devouring individuals of their own species, while their larvae are equally predaceous. They are exceedingly numerous in temperate regions, and are eminently serviceable in checking the increase of insects which feed on fruit and grain. The mandibles, by which they seize and tear their living prey, are long horny organs, hooked and sharp at the points, and toothed on the inner edges. This group includes the Tiger Beetles, Cicindelidae ( Plate VI. figs. 4, 9-12), so called from the fierceness of their disposition, and probably also from the spots and stripes with w hich the elytra are generally adorned. Most of the epecies are diurnal, frequenting hot sandy districts, enjoying the bright sunshine, and flying for short distances with great velocity. They are elegant in form and adorned with brilliant metallic colours, the prevalent hue being a golden green. The habits of the larvae of these insects are very remarkable. Unfit, from the softness of their bodies and the slowness of their motions, effectually to protect themselves from the attacks of their enemies, or to capture their prey on the surface of the ground, the larvae of the Tiger Beetles have recourse to stratagem in order to effect these purposes. By means of their short thick legs, assisted by their powerful sickle-shaped jaws, they dig burrows in the sandy banks which they frequent, vertical for some distance, and afterwards curving so as to become horizontal. These are about a foot in depth, and within them the Tiger Beetle remains during its larval and pupa stages. In seeking its food the creature makes its way from the bottom of its den until the head segment, which is broad and flat, reaches the level of the ground, and thus blocks up the aperture of its tunnel. It remains fixed in this position by means of two bent hooks placed on the upper surface of the 'eighth segment, which is considerably thicker than the others, until an unsuspecting ant or other insect passing over or close to it is seized by its formidable jaws and speedily conveyed to the bottom of the pit-fall, where it is greedily devoured. Should the tunnels of different individuals happen to come in contact, the more powerful larva is said to devour its weaker neighbour. When full grown it closes the mouth of its burrow and there undergoes metamorphosis. The best known and most beautiful of British species is the Tiger Beetle, Cicindela campestris, of a sea-green colour with six whitish spots on the elytra. When handled it exhales, according to Westwood, a pleasant odour like that of roses. Ground beetles (Carabidae) are generally less brilliant in colour than the Tiger forms, being more nocturnal in their habits, and with the jaws less formidably toothed. Many of the species are entirely apterous, with the elytra more or less soldered together, and the majority of them secrete an acrid juice which they expel when menaced or attacked. Of the latter the most remarkable are the Bombardier Beetles, Brachinus (Plate VI. fig. 8). These congregate together under stones, and when disturbed discharge a caustic fluid of an extremely penetrating odour, and so volatile that no sooner does it come in contact with the atmosphere than it passes into a vapour, accompanied by a considerable explosion, during which they seek to escape. When placed on the tongue this fluid causes a sharp pain and leaves a yellow spot somewhat similar to that produced by a drop of nitric acid. The Bombardiers are said to be capable of giving off as many as 18 of such discharges at a time. One of the most beautiful of European beetles is the Calosoma sycophanta (Plate VII. fig. 2), belonging to this group. Its body is of a deep violet colour, and the elytra, which are striated and punctured, are of a rich green and gold tint. Both in the larva and perfect states these beetles frequent the trunks and branches of the oak, where they find their favourite food—the large caterpillars of the Processionary Moth (Bombyx processionea), of which they devour enormous numbers, apparently undeterred by the hairs which clothe the body of the caterpillar, and which when seized by the human hand cause considerable pain. One of the most curious of Carabideous Beetles, Mormolyce phyllodes (Plate VI. fig. 5), is a native of Java. Its body is about 3 inches long and 1∣ inches across the elytra. The latter are flat, thin, and greatly dilated, while the other parts of the body are remarkably depressed, the beetle thus somewhat resembling the Orthopterous leaf-insects, and hence the specific name phyllodes, or leaf-like. Many of the ground beetles, such as the typical Carabi (Plate VI. figs. 6, 7) and the Calosoma, live in the sunshine and are generally brilliant in colouring; others spend their existence in subterranean caves, and are both colourless and blind; while such forms as Biennis areolatus, found on the coast of Normandy, live for the most part under water, being only found when the tide is low.
II. Hydradephaga, or Carnivorous Water Beetles, are oval and somewhat depressed in form, with the two posterior pairs of legs flattened and otherwise fitted for swimming. They include the Diving Beetles (Dytiscus) and the Whirligigs (Gyrinus). The former (Plate VII. figs. 3-7) occur in all quarters of the globe, and are truly amphibious, for although water is their favourite element, they survive for a long time on moist land, and most of them fly about in the evening and morning twilight with great power and speed. When needing to breathe they allow themselves to float on the surface of the water, raise their elytra, and expose their stigmata to the atmosphere, thus getting quit of exhausted air and obtaining a fresh supply, which is stored up by closing the elytra. They are exceedingly voracious, devouring aquatic insects, as Hy drophilus piceus, much larger than themselves, and doing considerable damage in fish ponds by devouring the young fish. They are readily kept in confinement, having been known to live thus for 3¾ years, feeding on raw beef and insects. The larvae are even more voracious than the perfect insects, sucking the juices of their prey through perforated mandibles, and protected from attack by their horny integuments. Whirligigs (Gyrinus) (Plate VII. figs. 10,11) differ from the Diving Beetles in the antennae, which are short and stout, and are so placed as somewhat to resemble ears. They are sociable creatures, and may be seen in ponds and ditches, congregated in groups varying from 2 to 100, swimming upon the surface with their backs above the water, and chasing each other in circles or darting about in more irregular gyrations. Unlike other water beetles their backs show a brilliant metallic lustre, and when darting about in the sunshine they look like pearls dancing on the surface. Their eyes are so divided as to appear to consist of two turned upwards and another pair looking downwards. The larvae (Plate VII. fig. 17) are long, slender creatures somewhat resembling small centipedes, having each of the abdominal segments provided with a pair of slender ciliated appendages employed as organs of respiration as well as of locomotion, while the last segment is provided with four hooked organs by means of which they leap about.
III. Philhydrida, or Water-loving Beetles, are aquatic or subaquatic in their habits, being found in the water or on the moist margins of ponds and marshes. Along with the two following groups they feed on decaying animal and vegetable substances, and for this reason those insects have been classed together as Rhypophaga, or Cleansers. The antennae are short and clavate, and they are specially distinguished from other aquatic forms by the great length of the maxillary palps, a feature which has procured for them the name Palpicornes, often applied to them. The best known forms belong to the family Hydrophilidee, of which one species, and that the largest, Hydrophilus piceus (Plate VII. fig. 32), is an inhabitant of Europe. This beetle is oval in form, and of a dark olive colour, and measures 1∣ inches in length. It uses its hind legs for swimming or rather paddling, moving them not together, as the true water beetles do, but alternately. Its movements in the water are thus slower than those of the former, but speed in this case is less necessary, their principal food consisting of aquatic leaves. In the larval stage, however, H. piceus makes an approach to the true water beetles in its food, and is so ferocious as to have earned the name ver assassin on the Continent. The mode of respiration in the perfect insect is curious; unable to raise its upper surface above the water, it merely protrudes its head, and folding its clubshaped antennae, the ends of which are slightly hollow, it thus conveys little bubbles of air beneath the surface of the water, where it brings them into contact with the tracheal openings. The larvae swim with facility, and are provided at the posterior extremity with two appendages which serve to maintain them at the surface when they ascend to breathe.
IV. Necrophaga are the beetles of most service in removing decaying animal matter, although a few species live õn putrescent fungi, and others resemble the carnivorous groups in attacking and devouring the larvae of other insects. They are chiefly marked by the form of the antennae, which are not much longer than the head, and get thickened or club-shaped at the extremity. This group comprises the Sexton Beetles (Necrophorus), of which Necrophorus vespillo (Plate VII. fig. 27) may be taken as the type. These insects have thick bodies and powerful limbs, and owe their popular name to the peculiar manner in which they provide a nidus for their eggs. Their sense of smell is exceedingly acute, and no sooner does one of the smaller quadrupeds, as mice or moles, die, than several of those burying beetles, gathering about, begin to remove the earth from beneath the dead animal, and in a few hours succeed in sinking the carcase beneath the level of the ground, which they then cover over with earth. Having thus prevented the body from being devoured by other carrion-eating animals, or from having its juices dried up by exposure to the sun, they make their way into the carcase and there deposit their eggs. Several individuals generally work together in this grave-digging operation, although Necrophorus germanicus is said to labour alone, and they have been known to show considerable intelligence in performing this operation; thus Gleiditsch states that in order to get possession of the body of a mole, fixed on the end of a stick, they undermined the latter and thus brought the dead body to the ground. The larvae on leaving the egg thus find themselves surrounded by an abundance of food; and when full grown they bury themselves fully a foot beneath the surface of the ground, where they form an oval chamber, the walls of which are strengthened by a coating of a gluey liquid, and in which they undergo metamorphosis. Shield Beetles (Silpha) (Plate VII. fig. 22)—so called from the flattened form of their bodies, feed chiefly on carrion; some, however, climb upon plants, particularly the stems of wheat and other grain, where they find small helices on which they prey; while others, as Silpha punctata, dwell on trees and devour caterpillars. They exhale a disagreeable odour, probably arising from the nature of their food, and when they are seized a thick dark-coloured liquid exudes from their bodies. The Dermestidae are a family of small but widely-distributed beetles, which work great havoc among skins, furs, leather, and the dried or stuffed animals in museums. The perfect insects are timid creatures, which when disturbed fold their short contractile feet under their bodies, and, remaining perfectly motionless, admirably counterfeit death. The mischief is mainly wrought by the larvae. These shed their skins several times, and take nearly a year in attaining their full growth. One of the most common and injurious species of this family is the Bacon Beetle (Dermestes lardarius) (Plate VII. fig. 14)—so called from its fondness for lard, but equally ready to attack the furrier’s wares. Their tastes are exceedingly general, as they have been known to destroy a whole cargo of cork and even to perforate asbestos. The larvae of Anthrenus museorum, a species not exceeding one-tenth of an inch in length, is exceedingly injurious to collections of insects, among which it eludes observation by its minuteness and by working in the interior of the specimens, which are thus ruined before the damage is observed.
V. Brachelytra (Plate VII. figs. 12, 15, 20) are readily distinguished from the other groups of beetles by having the elytra much shorter than the abdomen, although they still suffice to cover the long membranous wings, which when not in use are completely folded beneath. The abdomen is long and exceedingly mobile, and is employed in folding and unfolding the wings. It is furnished at its extremity with two vesicles which can be protruded or withdrawn at pleasure, and from which, when irritated, many species emit a most disagreeable odour, although in a few the scent is more pleasing; “one species,” says Kirby, “which I once took, smelt precisely like a fine high scented pear, another like the water-lily, a third like watercresses, and a fourth like saffron.” They are very voracious both in the larval and perfect states, feeding chiefly upon decaying animal and vegetable matters, although a few species devour living prey. Many of the smaller forms reside in and feed on mushrooms, some are found abundantly under putrescent plants, others in manure heaps, where they feed upon the maggots of flies, while there are a few forms which make their homes in the nests of the hornet and the ant. The larvae bear a considerable resemblance to their parents in form and habits, and have the terminal segment of the abdomen prolonged into a tube with two conical and hairy appendages attached. The Brachelytrous beetles form an extensive group, almost entirely confined to the temperate regions of the northern hemisphere, Great Britain alone possessing nearly 800 species. They are familiarly known in this country as Cock-tails, one of the largest and most familiar species being that known as the Devil’s Coach horse (Go'érius olens) It is about an inch in length, of a black colour, and its eggs are larger than those of any other British insect. It may often be seen crossing garden walks; and when approached or otherwise threatened, it immediately assumes a most ferocious aspect and attitude, elevating its head and opening wide its formidable jaws, raising and throwing back its tail after the manner of the scorpion, protruding its anal vesicles, and emitting a disagreeable odour. It is carnivorous.
VI. Glavicornes have the antennae terminating in a solid or perfoliated club, and include the Pill Beetles (Byrrhidsh and the Mimic Beetles (Histeridae). The former are small insects, generally short, oval, and highly convex, although a few species found under the bark of trees are flattened. They most frequently occur in sandpits and on pathways, and when in danger withdraw their highly contractile legs into cavities prepared for them on the under side of the body, at the same time folding up their antennae and remaining motionless. In this condition they may readily be mistaken for oval seeds or pills, hence the common name. The Mimic Beetles (Plate VII. fig. 13) seldom exceed one-third of an inch in length, and are of very solid consistence, their elytra being so hard that the pin of the entomologist is with difficulty made to enter. They are somewhat square in form, with the upper surface highly polished, feeding chiefly on putrid substances and found in great abundance in spring on the dung of oxen and horses. Like Pill Beetles they roll themselves up on the approach of danger and feign death with great perseverance, and to this they owe their generic name Hister, from histrio, a stage mimic.
VIL Lamellicornes comprise a vast assemblage of beetles, many of which, especially such as feed on flowers and living plants, are remarkable alike for beauty of form and splendour of colour. They are distinguished, by the form of their antennae, which always terminate in a club composed of several leaf-like joints, disposed like the spokes of a fan, the leaves of a book, or the teeth of a comb, or in a series of funnels placed above and within each other. The males often differ from the females in having horn-like projections on the head and thorax, and in the greater size of their mandibles. They are all winged insects, although somewhat dull and heavy in their flight; and alike in the larval and perfect states they are herbivorous, feeding either on living vegetation and flowers or on putrescent plants aud excrementitious substances. The following species may be regarded as illustrative of the most important subdivisons of the Lamellicorn Beetles :—Stag Beetles (Lucanidae) (Plate VIII. fig. 14), with the club of the antennae composed of leaflets disposed perpendicularly to its axis like the teeth of a comb, owe their most striking feature to the immense development of the mandibles in the males, the purpose served by these formidable looking organs being by no means fully understood. The males appear to be more numerous than the females, and fierce contests take place among the former for possession of the latter. The Stag Beetle (Lucanus cervus), of a uniform brown colour, measures 2 inches in length including the mandibles, and is the largest of British beetles. It inhabits woods, passing its immature stages in the interior of the oak and beech, and may be seen flying in the evening in search of the female. It has a patch of golden-coloured hair towards the base of the foreleg with which it cleans its antennae after these have been in contact with any sticky substance. After coupling and depositing their eggs both sexes soon die. The Dor Beetle (Geotrupes stercorarius) is the type of a large tribe of dung-eating beetles (Plate VII. figs. 21, 25, 26). It is a black insect, with brilliant metallic blue or purple reflections on the under side, and well known as “wheeling its drowsy flight” during fine evenings. This i t does in search of a patch of cow-dung, through which it makes its way until reaching the ground, where it bores a perpendicular tunnel about 8 inches deep, and as wide as a man’s finger; then ascending to the surface it conveys a quantity of dung to the bottom, and on this it proceeds to deposit an egg; another layer of the same material and another egg follow until the entire shaft is filled. The larvae on leaving the egg thus find themselves surrounded with their appropriate food. The Sacred Beetle of Egypt, Ateuchus sacer (Plate VII. fig. 29), somewhat resembles the Dor in form and habits. After depositing her egg on a piece of dung the female rolls the mass about in the sunshine with her forelegs until it forms a rounded ball. The process of hatching is thus accelerated, and a thin hardened crust is formed around the sôfter material inclosing the egg. A hole is then dug in the earth by means of its powerful forelegs, into which the ball is rolled and then covered over with earth, where it remains until fully developed. Those beetles show great perseverance in conveying the egg-laden pellets to their destination, frequently carrying them over rough ground on the broad flat surface of their heads, and seeking, when unable singly to complete the work, the assistance of their fellows. Two species of Sacred Beetles were worshipped by the ancient Egyptians, who regarded them as emblems of fertility, and as representing the resurrection of the soul, owing to their sudden appearance in great numbers on the banks of the Nile after the annual subsidence of that river. They form a conspicuous feature in the hieroglyphics of that nation, and are found sculptured on their monuments, sometimes of gigantic size. They were also formed into separate figures, as seals and amulets, made of gold and other precious materials, and hung around the necks of the living, or buried along with their mummies. The insect itself is sometimes found in their coffins. The male Hercules Beetle (Scarabaeus hercules) of Guiana has the head produced into an enormous horn, bent downwards at the extremity, and clothed on the under surface with a reddish brown pile, and measures 6 inches in length. The Cockchafers, Melolonthidce (Plate VII. fig. 28), have a short labrum and strong mandibles suited for feeding on leaves. The club of the antennae consists of a variable number of plates, those in the male being considerably elongated and resembling a folded fan (Plate VII. fig. 23). The common Cockchafer (Mélolordha vulgaris) is of a pitchy black colour clothed with a white pubescence or layer of minute scales. It is one of the commonest and most destructive of beetles, feeding in the perfect state on the leaves of the oak, beech, poplar, and elm, and sometimes appearing in such numbers as to utterly destroy the foliage over large districts; thus in the year 1688 they are said to have covered the hedges and trees in a district of Galway in such infinite numbers as to have hung in clusters like bees when they sw arm. When on the wing they almost darkened the light of day, and when feeding the noise of their jaws might have been mistaken for the sawing of timber. In a short time the foliage of the trees for miles round was so totally consumed that at midsummer the country wore the aspect of leafless winter. Destructive as they are in the perfect state they are still more injurious as larvae. The female buries herself beneath the surface of the ground and there deposits about 40 eggs. The larvae produced from these feed on the roots of grass and grain, thus “undermining,” according to Kirby and Spence, “the richest meadows, and so loosening the turf that it will roll up as if cut with a turfing spade.” These grubs continue their ravages for three years before undergoing metamorphosis, and thus do incalculable damage to the agriculturist. They are believed to have spread with the progress of agriculture, for it is only on soil rendered light and porous by tillage that they thrive. Enormous numbers of the grub are consumed by birds of the crow tribe, and it is principally in search of these that rooks so industriously follow the plough in England and France. The species is rare in Scotland. “Spinning” the cockchafer is a favourite but barbarous sport, practised by the boys of most countries in which this beetle commonly occurs, and seems to be at least as ancient as the time of Aristophanes, who refers to it in his Clouds as practised by the youth of Greece. Rose Beetles, Cetoniidae (Plate VIII. fig. 7), a beautiful tribe of insects, are distinguished from other Lamellicorn Beetles by the membranaceous character of their mandibles and maxillae. The Rose-Chafer (Cetonia aurata) is common in the south of England, where it feeds on the juices and petals of the rose, honeysuckle, and privet. It is about an inch long, of a brilliant-golden green above with coppery reflections beneath, and with whitish markings on the elytra. Its eggs are deposited among decayed wood, but certain species make use for this purpose of the nests of ants. The Goliath Beetles (Plate VIII. fig. 11) of tropical Africa are the largest of known Coleoptera, and their larvae form enormous cocoons of mud in which they undergo metamorphosis. One of these, Goliathus cacicus, is said to be roasted and eaten by the natives.
VIII. Serricornes form a group of beetles chiefly distinguished from the others by their elongate filiform antennae of equal thickness throughout, or tapering towards the extremity, but generally serrated or pectinated. They are subdivided into the Sternoxi, characterized by the solid consistence of their bodies, and by having the middle portion of the thorax elongated and advanced as far as beneath the mouth, and usually marked by a groove on each side, in which the short antennae are lodged, while the opposite extremity is prolonged into a point which is received into a cavity on the hinder part of the breast; and the Malacodermata, characterized by their bodies being generally, in whole or in part, of a soft or flexible texture, and by the absence of the prolongation just referred to. The Sternoxi include the Metallic Beetles, Buprestidae (Plate VII. figs. 18, 19) the most gorgeous of the Coleopterous families. “Nothing can exceed,” says Westwood, “the splendour of colour in many of the species, being decorated with the most brilliant metallic tints; some have a general coppery hue, whilst some present the beautiful contrast of fine yellow spots and marks upon a highly polished blue or green ground, and others exhibit the appearance of burnished gold or of rubies, inlaid on emerald or ebony.” The elytra of the Metallic Beetles are those usually employed in the embroidery of ladies’ dresses and for other purposes of personal ornament. They are most plentiful in the thick forests of tropical countries, and seem partial to the various species of fir-trees. They pass their larval· stage in the heart of timber, and there is an instance recorded of the escape of Buprestis splendens from the wood of a desk which had stood in one of the Guildhall offices for over twenty years. Springing Beetles, Elateridae (Plate VII. fig. 30), are narrower and more elongate than the former, and their legs are so short that when they fall on their backs they are as unable to right themselves as a capsized turtle, but by bending the head and thorax backwards, and making use of the prolongation already described, they are enabled to spring to a height fully ten times their own length, and this operation they repeat until they fall on their feet. The noise which accompanies the springing process has earned for them the name of Click Beetles. Some species of Elateridae are luminous iu the dark, and are known as Fireflies. A South American form diffuses during the night from its thoracic spots a strong and beautiful light sufficient to enable a person to read ordinary type, particularly if several are placed together in a glass vessel. By means of this natural illumination the women of the country can pursue their ordinary work, and ladies use this fire-fly as an ornament, placing it among their tresses during their evening promenades. The larva of Elater lineatus is known as the Wire-worm, a grub which often does great damage to tho turnip crop. The Malacodermata include the Glowworms, Lampyridae (Plate VII. fig. 1), of which the best known is the common Glow-worm (Lampyris noctiluca) (Plate VII. figs. 8, 9, 16), found in meadows and under hedges in England, but rare in Scotland. The male of this beetle has large wings and elytra, and flies swiftly, but the female is wingless and is a sluggish nocturnal creature; the latter, however, emits a beautiful phosphorescent light, by means of which the male, who is generally concealed by day in the trunks of trees, is directed to his mate. In the perfect insect the luminous matter chiefly occupies the under part of the three last segments of the abdomen, which differ from the rest in colour, being usually of a yellow hue, and the luminous property is apparently under the control of the Glow-worm, for when approached it may frequently be observed to diminish or extinguish its light. In form the larvae somewhat resemble the female, and possess in common with the pupae and eggs a slight degree of luminosity. The larvae are predaceous, attacking and devouring the smaller snails and slugs, Rut in the perfect state they become entirely herbivorous, only eating the tender leaves of plants. Many of the Afalacodermata are wood-borers; these include the Death-watch Beetles (Anobium), which as larvae perforate chairs, tables, and other wood-work in such numbers as usually to render the wood completely rotten. During the pairing season they make a noise like the ticking of a watch, by striking with their jaws against the object on which they rest. This is intended as a mutual call of the sexes, but it has long been regarded by the ignorant as of evil omen, hence the name, and the import of Gay’s words—
“The solemn death-watch clicked the hour she died.
Another species, Lymeτylon navale, abundant in the forests of Northern Europe, does great damage by boring into the timber of the oak tree.
Heteromera. —The beetles comprising this section have five joints to the first four tarsi, and four to the posterior pair, and form two groups, Trachelia and Atrachelia.
I. Trachelia have the head triangular or heart-shaped, and connected with the thorax by a kind of neck or abrupt pedicle. Most of the species in the perfect state live on various plants, of which they devour the foliage or suck the juices, and many when seized bend their heads, contract their limbs, and simulate death. This group includes the Oil Beetles (Melöe) (Plate VIII. fig. 2), large black insects, destitute of wings, and with short elytra. They secrete an oily fluid possessing slightly blistering properties, which when alarmed they emit from the joints of their legs, and when eaten by cattle, as they sometimes are when feeding on the wild buttercups of pasture-lands, they produce sores in the mouth. In some parts of Spain they are used instead of the Blistering Fly, or are mixed with it. The young ]arvae of several species of Oil Beetles, it has been ascertained, get conveyed to the nests of bees, where alone they can find their appropriate food, and where also they undergo metamorphosis. The most important insect of this group is the Spanish Fly, or Blistering Beetle (Lytta vesicatoria) (Plate VIII. fig. 19), found abundantly in SouthWestern Europe, but of rare occurrence in England. It is a handsome insect of a golden green colour, and measures about three-fourths of an inch in length. In Spain, where this species is most abundant, they are collected for commercial purposes in the month of June. A sheet is placed beneath the trees frequented by the blister-flies, and the branches are shaken, so as to cause the insects to fall off. They are then killed by exposure to the vapour of vinegar, and completely dried after they are dead. The blistering principle, known to chemists as cantharadin, is contained in their integuments. See Cantharides.
II. The Atrachelia have no distinct neck, the part of the head behind the eyes being immersed in the thorax. They are in most cases nocturnal insects, obscure in colour, and slow in motion. The Church-yard Beetle (Blaps mortisaga) (Plate VIII. fig. 1 ) is one of the commonest species. It is of a shining black colour, avoids the light, and emits an offensive odour. It is found in cellars, store-rooms, and the neglected parts of houses, feeding on rubbish of all kinds, and regarded as of evil omen by the superstitious. It is very tenacious of life, having been known to survive several hours immersion in spirits of wine, and cases are on record in which the larvae have been discharged from the human stomach. The Meal-worm is the larva of Tenebrio molitor (Plate VIII. figs. 4, 5), a well-known insect belonging to this group, which appears in the evening in the least frequented parts of houses. It is found abundantly in flour-mills and bake-houses, greatly relishing the heat of the latter. The larvae, which are long, cylindrical, and of an ochry yellow colour, pass their lives enveloped in the flour which forms their favourite food, and in the midst of which they become pupae. While injurious to flour and bran, and destroying great quantities of ship biscuits, the Meal-worm is used as bait by fishermen, and as food for the nightingale and other pet insectivorous birds.
Tetramera. —The beetles composing this section have four apparent joints to all the tarsi, but in most cases the tarsi are in reality five-jointed, the fourth being so minute as to have been overlooked by the founders of the tarsal system. For this reason Westwood proposed the term Pseudo-tetramera in place of Tetramera, a change which lias been adopted by several systematic writers. This section includes a vast number of small or moderate sized beetles, all vegetable feeders, found in the perfect state on flowers and plants. It is subdivided into the three following groups :—
I. Rhynchophora, the species of which are readily recognized by having the front of the head produced into a rostrum or snout, which bears the organs of the mouth at its extremity. The larvae are either entirely destitute of legs, or havfe them in the form of small fleshy tubercles, and are in most cases equally destitute of eyes. The most numerous and best-known tribe of Rhynchophorous beetles are the Weevils (Plate VIII. figs. 8, 9, 15, 16, 20, 22), of which several thousand species have been described, and whose larvae, dwelling in the interior of fruits and seeds, do immense damage to the produce of the farmer, the grain dealer, and the horticulturist. They are generally minute in size and exceedingly varied in colour, the South American forms, known as Diamond Beetles, being among the most gorgeous of insects. These owe their colour, which in the finest of them is a light-green tinged with golden yellow, to the presence of minute scales on the elytra. The Weevil par excellence (Calandra granaria) measures about one-eighth of an inch in length, is of a pitchy red colour, and does great damage in granaries. The female buries herself among the grains of wheat, in each of which she bores a small hole, where she deposits a single egg, thereafter closing the aperture with a glutinous secretion. The egg is soon hatched, and the larva, furnished with two strong mandibles, eats out the interior of the grain, becomes a nymph, and in the course of eight or ten days is transformed into the perfect insect, ready to raise another brood. The whole time occupied with their reproduction, from the union of the sexes to the appearance of the perfect Weevil, is not more than 50 days, and it has been calculated that from a single pair 23,600 individuals may thus take origin in a single season. Grain injured by these insects is readily detected, from the fact that it floats when immersed in water. Kiln-drying the grain is the mode most generally adopted for arresting the evil. Filberts, acorns, rice, the sugar-cane, and the palm tree have each its own species of Weevil. The Palm Tree Weevil (Calandra palmarum) is the largest of the tribe, measuring 2 inches in length, and its larvae, as well as those of the sugar-cane species, are, when cooked, considered delicacies by the natives of Guiana and the West Indies. Bruchus pisi (Plate VIII. fig. 12), belonging to another family of this group, deposits its eggs in peas, the interior of which is devoured by the larva. It has probably been introduced into Britain from America, where its ravages are occasionally such as totally to destroy the pea crop over large districts. The larvae of many species burrow beneath the bark of trees and thus destroy immense quantities of timber. Of these the most familiar are Scolytus destructor, whose curiously designed burrows in the bark of the elm are well known, and the Typographic Beetle (Tomicus typographicus), so called from the resemblance which its burrows, made in the soft wood Immediately beneath the bark, bear to printed characters.
II. Longicornes (Plate VIII. fig. 13) form an extensive group of beetles characteristic of tropical forests, and readily distinguished by the great length of their antennae, which in some cases are several times longer than the body. These are usually setaceous or filiform, and are occasionally adorned with tufts of hair at the joints (Plate VIII. fig. 3). The larvae of almost all the Longicorns live in the interior, or beneath the bark, of trees, perforating the timber of the largest forest trees, and thus hastening in these the natural process of decay. They are either apodal, or furnished with inconspicuous feet, but progress chiefly by the aid of small tubercles on the upper and under surfaces of the segments. The female is provided with an ovipositor of horny consistence, issuing from the posterior segment, by means of which the eggs are deposited in cracks and fissures of wood. The larvae remain for several years buried in the heart of timber, and in this way many exotic species are conveyed to this country, and are occasionally taken alive in the London and Liverpool docks. Several of the Longicorn Beetles are among the largest of Coleopterous insects, Prionus giganteus measuring 5 inches in length, while its eggs are nearly as large as those of the smaller birds. The Harlequin Beetle (shcrocinus longimanus), so called from the variety of its colouring, the grotesqueness of its markings, and the enormous elongation of its front pair of legs, is a South American species of this group, as is also the Musk Beetle (Callichroma ι moschata), one of the handsomest of our native species, and remarkable for the musky odour of its body.
III. Phytophaga comprise the tetramerous beetles which have neither the rostrum of the first group nor the lengthened antennae of the second. They are small insects of an oval or quadrate shape, and include the Golden Beetles, Chrysomelidae (Plate VIII. fig. 21), ornamented with metallic colours, among which blue, green, gold, and copper are conspicuous. The Turnip-fly (Haltica nemorum), a small species belonging to a family in which the posterior thighs are enlarged for leaping, devours the .young leaves of the turnip as soon as they appear above ground, and occasionally does immense injury to the turnip crop. Helmet or Tortoise Beetles, Cassidae (Plate VIII. figs. 20, 24), so called from the thorax and elytra overlapping so as to shield the limbs and abdomen on all sides, are oval, and in some cases almost square, flat insects, and often beautifully marked with combinations of green and golden hues, They are herbivorous, and are specially fond of artichoke and thistles. The larvae are provided at the posterior extremity with a two-branched fork, curved over the back, and usually bearing a pile of excrementitious matter, under which they lie partly concealed It can elevate or depress this stercoraceous parasol at pleasure, according as it needs shade or shelter. The Colorado Potato Beetle (Doτyphora decemlineata) belongs to the phytophagous family Ghrysomelidae. It measures nearly half an inch in length; its body is of a tawny or yellow cream colour, darkly spotted; and the elytra are marked with ten black longitudinal stripes. It is a native of the eastern slopes of the Rocky Mountains, where it fed on a wild solanaceous plant, Solanum rostratum, until the introduction of the potato plant, consequent on the settlement and cultivation of the “Far West,” provided it with what appears to have been a more appropriate food. Since 1859 it has travelled eastward, towards the more highly cultivated lands, at the rate of nearly 100 miles per annum, until it has reached the Atlantic Coast. It is now found over all the central and northern parts of the United States east of the Rocky Mountains, and throughout Canada, anti has already done incalculable mischief to the potato crops of those regions. The damage is chiefly wrought by the larvae, which are hatched on, and greedily devour, the leaves and stalk of the potato plant. They are said to produce three broods annually.
Trimera. —The majority of the beetles composing this section have only three apparent joints to the tarsi of all the feet, but a small articulation has been found to lie between the second and third joints, so that they are in reality four-jointed, aud for this reason Westwood has changed the name of the section to Pseudotrimera.
Trimerous beetles form a single group, the species of which are partly herbivorous, feeding on fungi (Plate VIII. figs. 17, 18), and partly carnivorous, devouring aphides or plant lice. The most familiar examples of this group are Lady-birds, Coccinellidae (Plate VIII. fig. 23), small convex insects of a black colour, spotted with red or yellow, or of a reddish colour, spotted with black. The larvae do great service by devouring the plant lice, which usually infest garden bushes. When alarmed the Lady-birds retract their limbs and emit a yellow juice from their joints, which has a very disagreeable odour. They occasionally occur in great numbers, extending for miles, in the south-eastern districts of England, where they are invaluable for freeing the hops of aphides. They walk slowly but fly well. The Seven-Spotted Lady-bird (f!occinella 7-punctata), the common species of Britain, is found in all quarters of the globe.
On Collecting and Preserving Coleopterous Insects. —The collector of beetles, in order to obtain perfect specimens, need not have recourse to the plan adopted by the lepidopterist of rearing the insect from the egg. The successful rearing of these is much more difficult than in the case of butterflies and moths, and the specimens so procured are generally inferior to those collected in the ordinary way. The complete life history, however, of comparatively few even of our native species has yet been fully traced; and although the collector thus might not greatly enrich his cabinet with specimens of his own rearing, yet by adopting this method he would almost certainly add to the general stock of knowledge regarding the transformations of these insects. Beetles may often be obtained in what may be termed accidental situations,—sand-pits into which they have fallen, or artificial traps set for them, as a white sheet spread on the grass; but “sweeping” and “beating” are the means mainly relied on by the coleopterist for filling his cabinet, and for these all the apparatus necessary consists of an umbrella-net and a stick for beating. The net is swept over the grass, and among the foliage of trees, and when the branches are shaken with the hand, or beaten with the stick, the net is held beneath to catch the falling insects. An umbrella inverted, or a sheet placed beneath the tree, serves the same purpose. A knowledge of the habits of the various tribes of beetles will give the collector a clue to the localities in which, and the time when, he may expect to find the species he is in search of. In this way the bark and timber of trees, decaying branches and leaves, putrescent fungi, the droppings and the dead bodies of mammals, fresh water ponds, and even the nests of wasps, bees, and ants will all be found to yield their own harvest of Coleoptera. Beetles when caught may either be dropped into a phial containing spirits of any kind, or into what is known as the “killing bottle,” the bottom of which contains cyanide of potassium covered over with a layer of gypsum. In either case, with few exceptions, the beetles die almost instantaneously. If kept too long in spirits, however, the limbs get loosened through maceration and fall off. The “setting” of a beetle, or of any other insect, consists in placing its limbs and antennae in a natural position and fixing them there by means of pins until they stiffen on a board on which there is a layer of cork. If not set when either moist or recent, they may be softened by being placed for a night in any small vessel containing a layer of wet sand, and covered with a damp cloth to prevent evaporation. The smaller beetles are usually mounted on card, each insect being stuck on a small dab of gum with its legs and antennae properly set; all others are pinned through the centre of the upper part of the right elytron. In the case of large beetles as much of the contents of the body as possible should be removed by making an opening in the abdomen; and with the Oil Beetles it is necessary to stuff the abdomen. This can be best effected by separating the latter from the body, emptying it, and refilling with wadding; it can then be readily gummed to the body. Mould may be got rid of by exposing the specimens to a strong heat for some hours, and mites and grease by washing the beetles with a small brush dipped in benzine. (j. gi.)
