COLEOPTEROUS INSECTS. 
107 
truncated before and behind, with a longitudinal 
groove down the middle. In other instances it is 
somewhat square, and occasionally it is nearly or- 
bicular. The inferior portion of the thorax is com- 
posed of a single piece named the sternum , or breast- 
bone. It is much developed in certain tribes, par- 
ticularly water-beetles ( Dytiscidce ), and in the beau- 
tiful species which constitute the genus Buprestis. 
Of the hinder portion of the thorax, the only part 
seen from above is a small piece, commonly of a 
triangular form, with its point projecting backwards 
and interposed between the suture, of the elytra at 
the base. This piece is termed the scutellum. It 
exists in a more or less obvious form in nearly all 
beetles, and although usually minute, it is sometimes 
so large (as in the genus Macraspis) as to occupy a 
considerable portion of the dorsal area. The ap- 
pendages of the thorax are the instruments of mo- 
tion, the w T ings and legs, on which it is necessary to 
bestow a brief consideration. 
The true organs of flight in the Coleoptera are 
two membranous and transparent wings, jointed 
upon the upper and hinder' portion of the thorax. 
They are generally very ample, and are extended 
by means of a few strong nervures which run in a 
longitudinal direction, and throw off a few lateral 
branchlets. When in a state of repose they are 
transversely folded, and in most cases completely 
covered by the first or upper pair of wings. The 
latter, as has been already stated, are of a hard or 
