George Herbert Carpenter

“ Most of the dominant families—such as the Carabidae (ground-beetles) , Scarabaeidae (chafers) , or Curculionidae (weevils) have a distribution as wide as the order. But while some large families, such as the Staphylinidae (rove-beetles) are especially abundant on the great northern continents, becoming scarcer in the tropics, others, the Cicindelidae (tiger-beetles) , for example, are most strongly represented in the warmer regions of the earth, and become scarce as the collector journeys far to south or north. ”

“ It bores through and enters the developing seed, where it undergoes a moult and becomes legless. Similarly the newly-hatched larva of an oil-beetle (Meloe) is an active little campodeiform insect, which, hatched from an egg laid among plants, waits to attach itself to a passing bee. Carried to the bee’s nest, it undergoes a moult, and becomes a fat-bodied grub, ready to lead a quiet life feeding on the bee’s rich food-stores.
Distribution and Habits.—The Coleoptera are almost world-wide in their distribution, being represented in the Arctic regions and on almost all oceanic islands. ”

“ This ball is buried in a suitable place, and serves the insect as a store of food. During summer the insects rest in their underground retreats, then in autumn they reappear to bury another supply of dung, which serves as food for the larvae. Fabre states that the mother-insect carefully arranges the food-supply so that the most nutritious and easily digested portion is nearest the egg, to form the first meal of the young larva. In some species of Copris it is stated that the female lays only two or three eggs at a time, watching the offspring grow to maturity, and then rearing another brood. ”

“ The little triungulins escape on to the body of the bee or wasp; then those that are to survive must leave their host for a non-parasitized insect. Clinging to her hairs they are carried to the nest, where they bore into the body of a bee or wasp larva, and after a moult become soft-skinned legless maggots. ”

“ Among the vegetable-feeding chafers we usually find that while the perfect insect devours leaves, the larva lives underground and feeds on roots. Such are the habits of the cockchafer (Melolontha vulgaris) and other species that often cause great injury to farm and garden crops (see Chafer) . Many of these insects, such as the species of Phanaeus (fig. 29) and Cetonia (fig. 30) , are adorned with metallic or other brilliant colours. The African “goliath-beetles” (fig. 31) and the American “elephant-beetles” (Dynastes) are the largest of all insects. ”

“ Hence we find that beetles of some kind can hold their own anywhere on the earth’s surface. Some climb trees and feed on leaves, while others tunnel between bark and wood. Some fly through the air, others burrow in the earth, while several families have become fully adapted to life in fresh water. A large number of beetles inhabit the deep limestone caves of Europe and North America, while many genera and some whole families are at home nowhere but in ants’ nests. ”

“ The larvae (fig. 2 c) are active, with well-chitinized cuticle, often with elongate tail-feelers (cerci) , and with five-segmented legs, the foot-segment carrying two claws.
The generalized arrangement of the wing-nervure and the nature of the larva, which is less unlike the adult than in other beetles, distinguish this tribe as primitive, although the perfect insects are, in the more dominant families, distinctly specialized. ”

“ Kolbe, on the other hand, insists that the weevils are the most modified of all beetles, being highly specialized as regards their adult structure, and developing from legless maggots exceedingly different from the adult; he regards the Adephaga, with their active armoured larvae with two foot-claws, as the most primitive group of beetles, and there can be little doubt that the likeness between larvae and adult may safely be accepted as a primitive character among insects. ”

“ There are four malpighian tubes. The larvae are furnished with large heads, powerful mandibles and well-developed legs, but the body-segments are feebly chitinized, and the tail-end is swollen. They feed in wood or spend an underground life devouring roots or animal excrement.
The Lucanidae or stag beetles (figs. 1 and 25) have the terminal antennal segments pectinate, and so arranged that the comb-like part of the feeler cannot be curled up, while the elytra completely cover the abdomen. ”

“ The males are very small, free-flying insects with the prothorax, mesothorax and elytra greatly reduced, the latter appearing as little, twisted strips, while the metathorax is relatively large, with its wings broad and capable of longitudinal folding. ”

“ The larvae (fig. 3) of some weevils live in seeds; others devour roots, while the parent-beetles eat leaves; others, again, are found in wood or under bark. The Scolytidae, or bark-beetles, are a family of some 1500 species, closely allied to the Curculionidae, differing only in the feeble development of the snout. They have clubbed feelers, and their cylindrical bodies (fig. 43) are well adapted for their burrowing habits under the bark of trees. Usually the mother-beetle makes a fairly straight tunnel along which, at short intervals, she lays her eggs. ”

“ Coming to the Tertiary we find the Oligocene beds of Aix, of east Prussia (amber) and of Colorado, and the Miocene of Bavaria, especially rich in remains of beetles, most of which can be referred to existing genera.
Classification.—The Coleoptera have been probably more assiduously studied by systematic naturalists than any other order of insects. The number of described species can now hardly be less than 100,000, but there is little agreement as to the main principles of a natural classification. About eighty-five families are generally recognized ”

“ The nervous system is remarkably concentrated in some beetles, the abdominal ganglia showing a tendency to become shifted forward and crowded together, and in certain chafers all the thoracic and abdominal ganglia are fused into a single nerve-centre situated in the thorax,—a degree of specialization only matched in the insectan class among the Hemiptera and some muscid flies. ”

“ Some families are very restricted in their range. The Amphizoidae, for example, a small family of aquatic beetles, are known only from western North America and Eastern Tibet, while an allied family, the Pelobiidae, inhabit the British Isles, the Mediterranean region, Tibet and Australia. The beetles of the British islands afford some very interesting examples of restricted distribution among species. ”

“ The larvae of the tortoise-beetles have the curious habit of forming an umbrella-like shield out of their own excrement, held in position by the upturned tail-process. The larvae of the beautiful, elongate, metallic Donaciae live in the roots and stems of aquatic plants, obtaining thence both food and air. ”

“ Various species among those that are predaceous attack smaller insects, hunt in packs crustaceans larger than themselves, insert their narrow heads into snail-shells to pick out and devour the occupants, or pursue slugs and earthworms underground. The vegetable-feeders attack leaves, herbaceous or woody stems and roots; frequently different parts of a plant are attacked in the two active stages of the life-history ”

“ Like the perfect insects, they are predaceous, feeding on plant-lice (Aphidae) and scale insects (Coccidae) . Their rôle in nature is therefore beneficial to the cultivator. The Endomychidae (fig. 33) , an allied family, are mostly fungus-eaters. ”

“ Luminous Organs.—The function of the stridulating organs just described is presumably to afford means of recognition by sound. Some beetles emit a bright light from a portion of their bodies, which leads to the recognition of mate or comrade by sight. ”

“ Of the four families included in this group, the Anthribidae (fig. 39) have jointed, flexible palps, feelers—often of excessive length—with a short basal segment, and the three terminal segments forming a club, and, in some genera, larvae with legs. There are nearly 1000 known species, most of which live in tropical countries. The Brenthidae are a remarkable family almost confined to the tropics; they are elongate and narrow in form (fig. 40) , with a straight, cylindrical snout which in some male beetles of the family is longer than the rest of the body. ”

“ The Gyrinidae, or whirligig beetles (fig. 9) , are a curious aquatic family with the feelers (fig. 9, b) short and reduced as in most Paussidae. They are flattened oval in form, circling with gliding motion over the surface film of the water, and occasionally diving, when they carry down with them a bubble of air. The fore-legs are elongate and adapted for clasping, while the short and flattened intermediate and hind legs form very perfect oar-like propellers. The larva of Gyrinus (fig. 9, c) is slender with elongate legs, and the abdominal segments carry paired tracheal gills. ”

“ Anchistopoda.—The families of beetles included by Kolbe in this group are distinguished by the possession of six malpighian tubes, and a great reduction in one or two of the tarsal segments, so that there seem to be only four or three segments in each foot; hence the names Tetramera and Trimera formerly applied to them. The larvae have soft-skinned bodies sometimes protected by rows of spiny tubercles, the legs being fairly developed in some families and greatly reduced or absent in others. As might be expected, degeneration in larval structure is correlated with a concealed habit of life. ”

“ There are either four or six malpighian tubes. A large number of families, distinguished from each other by more or less trivial characters, are included here, and there is considerable diversity in the form of the larvae. The best-known family is the Hydrophilidae, in which the feelers are short with less than eleven segments and the maxillary palpi very long. ”