CLASS INSECTA, 13 



but less solid in many insects, especially in the coleoptera. 

 We discover at the junction of these rings a small space more 

 firm than they, or of the same consistence, and each having a 

 stigma, so that the sides of the abdomen present a longitudi- 

 nal series of small pieces, where each segment is, as it were, 

 divided into four. Other pieces, equally corneous, occupy 

 the lower sides of the mesothorax and the metathorax, and 

 immediately under the origin of the elytra and the wings, 

 which are themselves supported on another piece disposed 

 longitudinally. The relations of these parts, the size and 

 form of the first articulation of the haunches, the manner in 

 which they articulate w^ith the semi-ring on which they de- 

 pend, the varying extent and direction of these semi-rings, 

 and the thorax, considered under this point of view, present a 

 combination of characters peculiarly advantageous for classi- 

 fication. Some naturalists, Knoch in particular, had already 

 employed them, but without any fixed principle, and with 

 arbitrary denominations. A necessary preliminary would 

 have been carefully to study the composition of the thorax, 

 and to pursue it comparatively into all the orders of this 

 class. The late Lachat, at my suggestion, had com- 

 menced this labour. His friend, M. Victor Audouin, has 

 pursued these researches, and has presented to the Academy 

 of Sciences a memoir on the subject, which has obtained its 

 suffrages. But it is also known by the general sketch given 

 of it by Baron Cuvier in his Report,* and by the extract 



* " An exposition of the parts of the thorax, and a fixed nomenclature 

 expressly created for them," says the Baron in his Report, " should natu- 

 rally be placed at the head of the work. The trunk of the insect may 

 always be divided into three rings, each of which bears a pair of feet, 

 and which M. Audouin names, according to their position, prothorax, 

 mesothorax, and metathorax. Beside these feet, the mesothorax 

 bears the first pair of wings, and the metathorax the second ; each of 

 these three segments is composed of four parts : one lower, two lateral, 



