98 NATURAL HISTORY OF 



as a part of the general history of particular groups 

 and species ; and we shall conclude these introduc- 

 tory observations by giving an account of the exter- 

 nal organs of coleopterous insects, in order that trie 

 descriptions and generic characters in the subse- 

 quent part of the volume may be more readily un- 

 derstood. 



The most characteristic feature of the coleopte- 

 rous order, and from which it obtains its name, has 

 been already mentioned, viz. the horny consistence 

 of the upper pair of wings. The whole body is 

 likewise covered with an integument or crust of a 

 similar nature, more or less rigid, which has been 

 found, on analysis, to consist chiefly of a peculiar 

 principle named chitine. This corneous envelope 

 defends the internal organs, and executes a function 

 analogous to that of the bones in vertebrate animals, 

 by supporting the softer parts, and affording points 

 of attachment to the muscles. 



It is one of the distinguishing attributes of' the 

 class of insects, that their bodies are inserted or di- 

 vided into many jointed parts, a mode of structure 

 which is more or less obvious in all their different 

 states of existence. These segments are more re- 

 gular and distinct in the larvae of the Coleoptera 

 than after the insects have undergone their final 

 transformation, by which some of the rings become 

 very much enlarged, while others suffer a corre- 

 sponding diminution. But in every perfect i 



