362 INSECTA. 



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*. The latter are inti- 

 mately united with the base of the abdomen, and their inferior por- 

 tion or pectus gives insertion to the second and third pairs of legs f. 

 The second, on which the scutellum 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 traversely folded. 

 Several species are apterous, but the elytra still exist. The abdomen 

 is sessile or united to the trunk in its greatest width. It is com- 

 posed externally of six or seven annuli, membranous above, or less 

 solid than underneath. The number of joints in the tarsi varies 

 from three J to five. 



The Coleoptera undergo a complete metamorphosis. The larva 

 resembles a Worm, having a scaly head, a mouth analogous to that 

 of the perfect Insect in the number of its parts, and usually six feet. 

 Some few species are destitute of them, or have merely simple mam- 

 millae. 



The pupa is inactive and takes no nourishment. The habitations, 

 mode of life, and other habits of these Insects, in both states, greatly 

 vary. 



I divide this order into four sections, according to the number of 

 joints in the tarsi. 



The first comprises the PENTAMERA, or those in which all the tarsi 

 consist of five joints, and is composed of six families, the two first of 

 which are distinguished from the others by a double excremental 

 apparatus . 



* The internal membrane, on each side, behind presents a stigma, a character 

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



f The mesothorax is always short and narrow, and the metathorax frequently 

 spacious, and longitudinally sulcated in the middle. 



J 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. 



According to M. Dufour the Silphce, a genus of our fourth family, also present 

 one ; it is unique, however, or but on one side. 



