INSECTA. 325 



were insufficient, and Mr. Kirby having already employed the denomi- 

 nation of metathorax, to designate the after-thorax, that of prothorax 

 and mesothorax, the ternary division once established, naturally pre- 

 sented itself to the mind, and the celebrated professor Nitzsch was the 

 first to employ it. Some naturalists have since designated the protho- 

 rax or anterior segment, that which bears the two rirst 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 consti- 

 tute 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 segments, into three areae, the antt-pectus, 

 medio-pectus, and post-pectus. The median line will also constitute 

 the sternum, which we divide into three parts : the ante-sternum, 

 media-sternum, and post-sternum. 



The teguments of the thoracic segments, as well as 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 flex- 

 ible 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 annulus itself, which 

 bears 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 inferior sides of the mesothorax and 

 metathorax and immediately under 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 coxjc, the manner 

 in which they are articulated with the semi-annulus to' which they 

 belong, the extent and direction of that semi-annulus varying, furnish 

 the thorax, thus considered, with a combination of characters, which in 

 a systematic point of view are of great importance. 



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

 sorts of locomotive organs, wings undjeet, which, in several, act asjins. 



The wings are membranous, dry, elastic organs, usually diaphanous, 

 and attached to the sides of the back of the thorax : the first, when there 



