286 



THE MECHANICAL FUNCTIONS. 



tion of a longitudinal axis. The principal portions 



into which the body is 

 divided are the head., the 

 trimk, and the abdomen: 

 each of which is com- 

 posed of several segments. 

 I have here given in illus- 

 tration, the annexed fig- 

 ures, showing the succes- 

 sive portions into which 

 the solid framework, or 

 skeleton, of one of the 

 beetle tribe, the Calosoma 

 st/cophanla* may be separated. The entire insect, 

 which presents the most perfect specimen of a 

 complete skeleton in this class of animals, is re- 

 presented in Fig. 149 ; and the several detached 

 segments, on an enlarged scale, in Fig. 150. The 

 head (c), as seen in the latter figure, may be 

 regarded as being composed of three segments ; 

 the trunk (x, y, z,), of three ; and the abdomen (b), 

 of nine. Fig. 151, is a view of the head separated 

 from the trunk, and seen from behind, in order to 

 show that its form is essentially annular, and that 

 it resembles in this respect the rings of which the 

 thorax consists, and to which it forms a natural 

 sequel. 



The head contains the brain, or principal en- 

 largement of the nervous system, and the organs 

 of sensation and of mastication. Its size, as com- 

 pared with the rest of the body, varies much in 

 different insects, and is in general proportionably 



Cai'abtis sycophanta. Linn. 



