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 (DytiscidcB)^ 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 wings 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 



