STRUCTURE OF INSECTS. 



227 



ly, entomoline. The purposes served by the hairs are not 

 always obvious. In many cases they seem intended to pro- 

 tect the integuments from the water, which they repel from 

 their surfaces. They also tend to prevent injury arising 

 from friction; and are found to be more abundant in those 

 parts, as the joints, vvhich are liable to rub much against one 

 another. 



The divisions of the body are frequently marked by deep 

 incisions; whence has originated the term insect, expressive 

 of this separation into sections. It is, however, a character 

 which they possess in common with all articulated animals, 

 the typical form of which consists, as we have seen, of a se- 

 ries of rings, or segments, joined endwise in the direction of 

 a longitudinal axis. The principal portions into which the 



body is divided are the heady 

 the trunk, and the abdomen: 

 each of which is composed of 

 several segments. I have here 

 given, in illustration, the an- 

 nexed figures,showing the suc- 

 cessive portions into which 

 the solid frame-work, or ske- 

 leton, of one of the beetle 

 tribe, the Calosoma syco- 

 phanta,"* may be separated. 

 The entire insect, which pre- 

 sents the most perfect speci- 

 men of a complete skeleton in this class of animals, is repre- 

 sented 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. 



■4>. 



• Carnhus sycophanta. Linn. 



