COLEOP'TERA, or COLEOP'TEROUS INSECTS (Gr. koleos, a sheath; and pteron, a wing), an order of insects which, with a little change of limits and characters, has been recognized since the days of Aristotle. The number of species enumerated by nat uralists, and of which examples are gathered in museums, amounts to many thou sands. The C. are sometimes collectively called beetles, although that name is gen erally more limited in its application, and many of them are known by other names, as weevils, lady-bugs, etc. The glow-worm and the blistering-fly (canthaa) belong to this order.
The C. may be described as four-winged insects, which have the first pair of wings converted into crustaceous wing-cases (elytra), and the second pair of wings folded cross wise under these when not in use. lu some of them, the membranaceous wings are wanting, or rudimentary, in one or in both sexes, for there is often a difference of the sexes in this respect: more rarely, the elytra also are wanting in one sex, as in the female glow-worm. The head an anteMne vary extremely in different C., the antenna; often differ considerably in the male and female of the same species. The first segment of the thorax (prothora.r) is greatly larger than the other two. The abdomen is united to the thorax by its whole width, and not by a stalk. C. have two composite eyes, and no additional simple or stemmatic eyes (ocelli). The mouth is fitted for cutting, gnawing, tearing, or chewing, but never at all for suction, and exhibits in the greatest perfection of development the complicated structure which belongs to the mouth of all the masticating or mandibulated insects. See INSECTS. The upper jaws or mandibles
are hard and horny in most of the C., but comparatively soft in those which feed on vegetable juices, or on putrescent animal matter. The food of the C. is very various: some prey on other insects, worms, etc.; some feed on carrion; some on rotten wood— some on wood in a fresh and growing state—some on the roots of grasses and other plants—some on grain—some on leaves—some on tlowers, etc. The food of their larvte is equally various; but perfect insects and larvre generally agree in being very vora cious. Their digestive organs exhibit great diversities, according to the kinds of their food. The C. are among the insects which undergo complete transformations, and of which the pupa is inactive. The larva (grub) is generally like a short thick worm, with a scaly head and mouth, generally with six legs, of which, however, some species are destitute. Coleopterous insects are distributed over all parts of the world, but are most abundant within the tropics, where also they attain their greatest size and greatest brilliancy of colors. The splendor of the metallic tints exhibited by ninny of the trop ical species is not excelled in nature. The order, however, contains also many species of dull hue, and sufficiently unattractive appearance. Many of the C. are noted for the mischief which they do to crops, stores of provisions, timber, and articles of furniture, trees, etc.; few of them are of any immediate use to man, the principal of these being the blistering-flies or cantharides.