48 DEFINITION OF THE TERM INSECT. 



the expense of others, and a variation in form takes place, 

 none, as M. Savigny has elaborately proved, are totally 

 obliterated or without some representative 11 . The organs 

 now described, except the upper lip, are formed after 

 a quite different type from those of Vertebrata, with which 

 they agree only in their oral situation and use. 



The second portion of the body is the Trunk, which 

 is interposed between the head and abdomen, and in 

 most insects consists of three principal segments, sub- 

 divided into several pieces, which I shall afterwards ex- 

 plain to you. I shall only observe, that some slight ana- 

 logy may perhaps be traced between these pieces and the 

 vertebrae and ribs of vertebrate animals, particularly the 

 Chelonian reptiles. This is most observable in Gryllus L. 

 and Libellula L., in which the lateral pieces of the trunk 

 are parallel to each other 5 . In the Dijptera and many 

 of the Aptera most of these pieces are not separated by 

 sutures. Each of the segments into which the trunk is 

 resolvable bears a pair of jointed legs, the first pair point- 

 ing to the head, and the two last to the anus. These le«-s 

 in their composition bear a considerable analogy to those 

 of quadrupeds, &c, consisting of hip, thigh, leg, and 

 foot ; but the last of these, the foot or Tarsus, is almost 

 universally monodactyle, unless we regard the Calcaria 

 that arm the end of the tibia, as representing fingers or 

 toes, an idea which their use seems to justify. Acheta 

 monstrosa and Tridactylus paradoxus, however c , exhibit 

 some appearance of a phalanx of these organs. They 

 differ from them first in number, the thoracic legs beino- 



% Anim. sans Vertebr. I. i. Mem. i. 



b Plate VIII. Fig. 10—14; IX. Fig. 6—8. 



c Coquebert Illust. Ic. iii. /. xxi.f. 3. 



