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 the 
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 chiline . 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 bisected 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 insect 
