CHAPTER IV. 
Jointed Animals,— continued . 
Insects, — continued. 
The Beetles, —Order Coleoptera. 
The beetles are in general easily distinguished from all other insects, and though 
they seem almost endless in their variety, and comprise an immense number of 
distinct specific forms, constitute a very well defined order. The chief characters 
that serve to distinguish them are briefly as follows. They undergo a complete 
metamorphosis. Their mouth—which is fitted for taking in solid food—is furnished 
with biting jaws (mandibles), a pair of maxillse with palpi, and an undivided, or 
very slightly divided lower lip (labium), which also bears palpi. The antennse are 
extremely variable in form, but seldom possess more than eleven joints. The 
prothorax is usually large and is freely articulated with the following segment 
(mesothorax), over which it fits behind in such a manner as almost to completely 
cover it on the upper side. The fore-wings are converted into a pair of stiff horny 
structures called elytra, which, in a state of rest, usually meet by their edges in a 
straight line along the middle of the back, and serve to protect the liind-wings and 
the soft hind-parts of the body. The hind-wings are in beetles the only true 
organs of flight; these are membranous and transparent, provided with few 
nervures, and when not in active use are generally folded transversely beneath 
the elytra. Many beetles are without hind-wings and are said to be apterous; but 
it is to be remembered that very few beetles, except in the larval state, are com¬ 
pletely apterous in the sense of being without both hind-wings and elytra. In the 
wingless species the elytra are generally well developed, and frequently fastened 
together along the suture where they meet. The presence of elytra, though not 
exclusively peculiar to beetles, is still one of their most characteristic features, and 
affords in most cases a ready means of recognising them. Elytra very similar to 
those of some Coleoptera are, however, met with among the ear-wigs; and the 
elytra of beetles do not invariably meet in a straight suture. Thus in the oil- 
beetles {Meloe) one elytron folds partly over the other; while in certain other 
groups, the Rhipiphoridce for example, the elytra are of such a form that they 
either do not meet at all, or only just touch at the base, and are sometimes so small 
and so little like the ordinary elytra of beetles that their true nature is not at first 
sight very apparent. 
We have alluded above to the great variety that is to be met with among 
beetles. No insects exhibit greater extremes of size; and we find on the one 
hand beetles so small that a pin’s head is large in comparison, while on the other 
