Fig. 469.—Bacon Beetle (Dermestes lardarius), magnified and natural size.
Fig. 470.—Attagenus pellio, magnified and natural size.
The Anthrenus museorum, the fifteenth of an inch in length, black, with three grey bands, drives collectors to despair, for its larva destroys their collections. It is covered with grey and brownish hairs, which it bristles up the moment it is touched. The perfect insect feeds on flowers, and counterfeits death when seized. All possible means have been tried for getting rid of the Anthrenus by placing in the collection camphor, benzine, tobacco, sulphur, &c., but benzine very soon destroys them.
Fig. 471.—Hydrophilus piceus.
The Hydrophili, very different to the group which we shall presently consider, are herbivorous, and are to be found on the leaves of aquatic plants. The Hydrophilus piceus ([Fig. 471]), which attains to an inch in length, is common in our fresh waters. It must not be seized without taking precautions, as its breast is provided with a strong point, which pierces the skin. It draws in air by thrusting its antennæ out of the water, and placing them against its body, the bubbles of the air, which get involved in a sort of furrow, slip under the body, and fix themselves to the hair, in such a manner that the animal seems to be clothed in pearls. It is thus the air reaches the spiracles. The female of the Hydrophilus is sometimes seen clinging to aquatic plants, head downwards, forming her cocoon, terminated by a long pedicle, in which she places her eggs, by means of the two bristles situated at the extremity of the abdomen ([Fig. 472]). After having drawn this after her for some time, she leaves it to itself in calm water. At the end of a fortnight there come out from it little brown larvæ, very active, which ascend the water plants. These larvæ are at the same time herbivorous and carnivorous. They live on plants and small molluscs, which they seize from underneath, and whose shell they break by pressing them against their back, to extract from it the animal. If attacked, they emit a black liquid, which discolours the water, and enables them to escape. At the end of two months the larva comes out of the water, and burrows into the ground to undergo its metamorphosis into a pupa ([Fig. 473]), which becomes a perfect insect a month afterwards. The latter gets its colour little by little, and comes out of the ground at the end of twelve days. According to M. Dumeril, the intestine of the larva grows gradually longer and longer, and its diet becomes that of herbs, the adult preferring vegetable food to animal matter. It is at the end of summer that the Hydrophilus piceus becomes perfect, and it passes the winter in a state of torpor at the bottom of the water. The females lay in the month of April. A small species, Hydrous caraboides, is commoner than the large one; its body is more rounded behind.