CLASS INSECTA. 



11 



ovir language (French) by that of corselet {corslet). It is 

 composed of three segments, which at first were not well dis- 

 tinguished, and whose relative proportions vary. Sometimes, 

 as in the coleoptera, the anterior one, by much the largest, 

 separated from the following by an articulation, mobile, and 

 alone discovered, appears at the first glance to compose of 

 itself the whole trunk, and bears the name of thorax or cors- 

 let. Sometimes, as in the hymenoptera, the lepidoptera, &c. 

 much shorter than the succeeding one, it has the form of a 

 collar, and constitutes, with the other two, a common body 

 attaching to the abdomen by a pedicle, or intimately united 

 with it in all its hinder breadth, and this is again called 

 thorax. These distinctions, established on this particular, 

 were insufficient and often ambiguous, seeing that they did 

 not rest on a ternary division which I have strictly an- 

 nounced in the first edition of this work as a character pro- 

 per to the hexapod insects, Mr. Kirby having already em- 

 ployed the denomination of metathorax, to distinguish the 

 hinder thorax,* those oi prothorax and mesothorax, the ter- 



* This segment ought not to be restrained in the hymenoptera, to this 

 superior division of the thorax, very short and transverse, on the sides 

 of which the second wings are inserted ; it is formed, besides, of that 

 thoracic portion which extends hindwards, as far as the origin of the ab- 

 domen, and this is what evidently proves the position of the last two 

 stigmata of the trunk, since they are placed on the sides of this extremity, 

 behind the wings and above the last two feet. I am even of opinion, that 

 this observation should apply to all winged insects. Their metathorax 

 will be divided, at least in the upper part, into two portions or demi-seg- 

 ments, the one bearing in the tetroptera, the second wings, and without 

 stigmata, and the other being provided with them. This last sometimes 

 appears to depend on the abdomen, as in almost all the insects, with the 

 exception of the hymenoptera, with pedicled abdomen, the rhipiptera, 

 and the diptera j sometimes it is incorporated with the trunk or thorax, 

 and closes it behind, as in these last insects : it is on this account, that I 

 have named the second division of the metathorax, the mediary segment ; 



