The appendages of the body are:—(1) a pair of antennae; (2) the trophi, constituted by three pairs of mouth-parts; (3) three pairs of legs; (4) the wings[19]; (5) abdominal appendages of various kinds, but usually jointed. Before considering these in detail we shall do well to make ourselves more fully acquainted with the elementary details of the structure of the trunk. In the adult Insect the integument or crust of the body is more or less hard or shell-like, sometimes, indeed, very hard, and on examination it will be seen that besides the divisions into segments and into dorsal, ventral, and pleural regions, there are lines indicating the existence of other divisions, and it will be found that by dissection along these lines distinct pieces can be readily separated. Each hard piece that can be so separated is called a sclerite, and the individual sclerites of a segment have received names from entomotomists. The sclerites are not really {92}quite separate pieces, though we are in the habit of speaking of them as if such were the case. If an Insect be distended by pressure from the interior, many of the sclerites can be forced apart, and it is then seen that they are connected by delicate membrane. The structure is thus made up of hard parts meeting one another along certain lines of union—sutures—so that the original membranous continuity may be quite concealed. In many Insects, or in parts of them, the sclerites do not come into apposition by sutures, and are thus, as it were, islands of hard matter surrounded by membrane. A brief consideration of some of the more important sclerites is all that is necessary for our present purpose: we will begin with the head. [Illustration: FIG. 49.—Capsule of head of beetle, _Harpalus caliginosus_: A, upper; B, under surface: _a_, clypeus; _b_, epicranium; _c_, protocranium; _d_, gula; _e_, facetted eye; _f_, occipital foramen; _g_, submentum; _h_, cavity for insertion of antenna.]