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 maxillae with palpi, and an undivided, or 

 very slightly divided lower lip (labium), which also bears palpi. The antennae 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 hind-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 



