Fam. 61. Buprestidae.—Antennae serrate, never elongate; prothorax fitting closely to the after-body, with a process received into a cavity of the mesosternum so as to permit of no movements of nutation. Five visible ventral segments, the first usually elongate, closely united with the second, the others mobile. Tarsi five-jointed, the first four joints usually with membranous pads beneath. This family is also of large extent, about 5000 species being known. Many of them are remarkable for the magnificence of their colour, which is usually metallic, and often of the greatest brilliancy; hence their wing-cases are used by our own species for adornment. The elytra of the eastern kinds of the genus Sternocera are of a very brilliant green colour, and are used extensively as embroidery for the dresses of ladies; the bronze elytra of Buprestis (Euchroma) gigantea were used by the native chieftains in South America as leg-ornaments, a large number being strung so as to form a circlet. The integument of the Buprestidae is very thick and hard, so as to increase the resemblance to metal. The dorsal plates of the abdomen are usually soft and colourless in beetles, but in Buprestidae they are often extremely brilliant. The metallic colour in these Insects is not due to pigment, but to the nature of the surface. Buprestidae appear to enjoy the hottest sunshine, and are found only where there is much summer heat. Australia and Madagascar are very rich in species and in remarkable forms of the family, while in Britain we possess only ten species, all of which are of small size, and nearly all are excessively rare. The family is remarkably rich in fossil forms; no less than 28 per cent of the Mesozoic beetles found by Heer in Switzerland are referred to Buprestidae.
Fig. 136—A, Larva of Euchroma goliath (after Schiödte); B, imago of Melanophila decostigma. Europe.
The larvae (Fig. 136, A) find nourishment in living vegetable matter, the rule being that they form galleries in or under the bark of trees and bushes, or in roots thereof; some inhabit the stems of herbaceous plants and one or two of the smaller forms have been discovered to live in the parenchyma of leaves. A few are said to inhabit dead wood, and in Australia species of Ethon dwell in galls on various plants. Buprestid larvae are of very remarkable shape, the small head being almost entirely withdrawn into the very broad thorax, while the abdomen is slender.[[135]] A few, however, depart from this shape, and have the thoracic region but little or not at all broader than the other parts. The larvae of Julodis—a genus that inhabits desert or arid regions—are covered with hair; they have a great development of the mandibles; it is believed that they are of subterranean habits, and that the mandibles are used for burrowing in the earth. Only the newly hatched larva is, however, known.
Series IV. Heteromera.
Tarsi of the front and middle legs with five, those of the hind legs with four, joints.
This series consists of some 14,000 or 15,000 species. Twelve or more families are recognised in it, but the majority of the species are placed in the one great family, Tenebrionidae. The number of visible ventral segments is nearly always five. Several of the families of the series are of doubtful validity; indeed beyond that of Tenebrionidae the taxonomy of this series is scarcely more than a convention. The larvae may be considered as belonging to three classes; one in which the body is cylindrical and smooth and the integument harder than usual in larvae; a second in which it is softer, and frequently possesses more or less distinct pseudopods, in addition to the six thoracic legs; and a third group in which hypermetamorphosis prevails, the young larvae being the creatures long known as Triungulins, and living temporarily on the bodies of other Insects, so that they were formerly supposed to be parasites.
Fam. 62. Tenebrionidae.—Front coxae short, not projecting from the cavities, enclosed behind. Feet destitute of lobed joints. Claws smooth. This is one of the largest families of Coleoptera, about 10,000 species being already known. A very large portion of the Tenebrionidae are entirely terrestrial, wings suitable for flight being absent, and the elytra frequently more or less soldered. Such forms are described in systematic works as apterous. Unfortunately no comprehensive study has ever been made of the wings or their rudiments in these "apterous forms."[[136]] it is probable that the wings, or their rudiments or vestiges, always exist, but in various degrees of development according to the species, and that they are never used by the great majority of the terrestrial forms. Many of the wood-feeding Tenebrionidae, and the genera usually placed at the end of the family, possess wings well adapted for flight. The apterous forms are chiefly ground-beetles, living in dry places; they are very numerous in Africa, California, and North Mexico. Their colour is nearly always black, and this is probably of some physiological importance; the integuments are thick and hard, and if the wing-cases are taken off, it will be found that they are usually more or less yellow on the inner face, even when jet-black externally; the external skeleton is very closely fitted together, the parts that are covered consisting of very delicate membrane; the transition between the hard and the membranous portions of the external skeleton is remarkably abrupt. These ground-Tenebrionidae form a very interesting study, though, on account of their unattractive appearance, they have not received the attention they deserve.
Fig. 137—Tenebrio molitor. Europe, etc. A, Larva (meal-worm); B, pupa (after Schiödte); C, imago.