COLEQL'TEUA. 265 



none simple(l); and a mouth consisting of a labrum, two 

 mandibles, usually of a scaly substance, two jaws, each fur- 

 nished with one or two palpi, and of a labium formed of two 

 pieces, the mentum and the ligula, and accompanied by two 

 palpi, commonly inserted into the latter. Those of the jaws, 

 or when they have two, the exterior ones, never consist of 

 more than four joints ; those of the lip usually have three. 



The anterior segment of the trunk, or that which is before 

 the wings, usually called the corselet, bears the first pair of 

 legs, and is much larger than the two other segments(2). The 

 latter are intimately united with the base of the abdomen, and 

 their inferior portion or pectus gives insertion to the second 

 and third pairs of legs(3). The second, on which the scutel- 

 lum is placed, is narrowed before, and forms a short pedicle 

 which fits into the interior of the first, and serves as a pivot, 

 on which it moves. 

 . The elytra and wings arise from the lateral and superior 

 edges of the metathorax. The elytra are crustaceous, and 

 when at rest, join along their internal margin, and always 

 horizontally. They almost always conceal the wings, which 

 are wide and transversely folded. Several species are apter- 

 ous, but the elytra. still exist. The abdomen is sessile or 

 united to the trunk in its greatest width. It is composed ex- 

 ternally of six or seven annuli, membranous above, or less solid 

 than underneath. The number of joints in the tarsi varies 

 from three(4) to five. 



The Coleoptera undergo a complete metamorphosis. The 



(1) In some of the Brachelytra two small yellowish points have been observed, 

 that have been taken for ocelli: but without, as I imagine, any careful examina- 

 tion, particularly as the Forficulae, a genus of the Orthoptera that is nearest to the 

 Coleoptera, exhibit none. 



(2) The internal membrane, on each side, behind, presents a stigma, a charac- 

 ter which I believe had not yet been observed, although it was presumed to exist. 



(3) The mesothorax is always short and narrow, and the metathorax frequently 

 spacious, and longitudinally sulcated in the middle. 



(4) If we may judge from analogy, the Coleoptera, termed Monomera, have 

 probably three joints in the tarsi, the two first of which escape observation; this 

 section and that of the Dimera have been suppressed. 



Vol IIL 2 I 



