INSECTA. 
362 
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 ov pectus gives insertion to the second and third pairs of legsf. 
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 Avide and travei’sely folded. 
Several species are ajiterous, but the elytra still exist. The abdomen 
is sessile or united to the trunk in its greatest Avidth. 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 feAV species are destitute of them, or have merely simple mam- 
millee. 
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 AA^hich all the tarsi 
consist of five joints, and is composed of six families, the tAVO first of 
Avhich are distinguished from the others by a double excremental 
apparatus §. 
* The internal membrane, on each side, behind presents a stigma, a charaeter 
which I believe had not yet been observed, although it was presumed to exist. 
f The raesothorax 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, 
