344 INSECTA, 



Kirby having already employed the denomination of metathorax, 

 to designate the after-thorax, that of prothorax and mesothorax, the 

 ternary division once established, naturally presented itself to the 

 mind, and the celebrated professor Nitzsch was the first to employ 

 it. Some naturalists have since designated the prothorax or ante- 

 rior segment, that which bears the two first feet, by the term collar, 

 collare. Wishing to retain the denomination of corselet, but to 

 restrain its application within proper limits, we will employ that 

 term in all those cases where this segment is much larger than the 

 others, and where these latter are joined to the abdomen, and seem 

 to constitute an integral part of it a disposition proper to the 

 Coleoptera, Orthoptera, and several of the Hemiptera. When 

 the prothorax is short, and forms with the succeeding segments a 

 common and exposed mass, the trunk composed of the three will 

 retain the name of thorax. We will also continue to style pectus 

 the inferior surface of the trunk, dividing it according to the seg- 

 ments, into three areas, the ante-pectus, medio-pectus, and post-pec- 

 tus. The median line will also constitute the sternum, which we 

 divide into three parts: the ante-sternum^ medio-sternum, and post- 

 sternum. 



The teguments of the thoracic segments, as well as of those of 

 the abdomen, are usually divided into two annuli or semi-annuli, the 

 one dorsal or superior, the other inferior, laterally united by a soft 

 and flexible membrane, which, however, is but a portion of the same 

 tegument that in many Insects, the Coleoptera particularly, is less 

 firm. At the point of junction between these annuli we observe a 

 little space of a more solid texture, or of the consistence of the an- 

 milus itself, which bears a stigmata, so that the sides of the abdomen 

 present a longitudinal series of small pieces, or each segment seems 

 to be quadripartite. Other equally corneous pieces occupy the in- 

 ferior sides of the mesothorax and metathorax and immediately un- 

 der the origin of the elytra and wings, which are supported by 

 another longitudinal piece. The relations of these parts, the size 

 and form of the first joint of the coxse, the manner in which they 

 are articulated with the semi-annulus to which they belong, the ex- 

 tent and direction of that semi-annulus varying, furnish the thorax, 

 thus considered, with a combination of characters, which in a sys- 

 tematic point of view are of great importance. 



As Insects inhabit all kinds of dwellings, they are provided with 



