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 character- 

 istics 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 fur- 

 nished 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 completely 

 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 recognizing them. Elytra very similar to those of 

 some Coleoptera are, however, met with among the earwigs; 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 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 we get 



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