Page:Popular Science Monthly Volume 39.djvu/243

Rh second pair of wings, which are always membranous when they are not atrophied, and the third pair of legs. The ventral part of the thorax is called the sternum, and the lateral pieces are the epimera. The wings, usually four, are sometimes reduced to two, and may even disappear entirely, when the insect is said to be apterous. The two pairs of wings, when they exist, are unlike, as in the Coleoptera and bugs, or alike, as in the Hymenoptera and Neuroptera. When they are unlike, those of the first pair have a horny consistency. They form a protecting case for the wings of the second pair, and are called elytra; the wings of the second pair are membranous, and are supported only by a network of nerves, which forms a kind of framework for them. Of this character are the wings of the cockchafer and stag-beetle. In the elytrum we distinguish the base, or part adjacent to the prothorax; the shoulder, or fore-external part; the humeral callosity, a more or less pronounced lump near the shoulder; the suture, an inner part, by which the elytra at rest are in contact; the humeral angle, or external basilar angle (of the side of the shoulder); the scutellary angle, or inner basilar