302 NATURAL HISTORY OF ARTHROPODS. 



them ■with flics and otlier insects, care beiniL; taken that the full-grown lar\iB have 

 opportunity to crawl out of the water and into moist sand, in which latter they pupate. 

 Carnivorous land-coleoptera are more difficult to rear. Where a large nuinlier of the 

 same species of beetle is reared at once, sjjecimens of each stage should be preserved 

 in alcohol, carefidly labelled, for future reference. 



In bodily form the Coleoptera present every variation from long cylindi-ical to 

 nearly globular, from hemisi)heres to extremely flattened discs, from straggling ant- 

 like forms to compact seed-like ones, as may be seen by examining tlie illustrations 

 which follow. Throughout all the diversity of form which environment has given 

 beetles, they invariably show, \\ith considerable distinctness, a division into three 

 parts, portions which, at first sight, might easily l)e mistaken for head, thorax, and 

 abdomen, but which more careful examination proves to be head, prothorax, or the 

 first of the three divisions of the thorax, and a portion, covered generally l)y the ely- 

 tra, which is composed of the mesothorax or middle portion of the thorax, the meta- 

 thorax or posterior part of the thorax, and finally the abdomen. The liead bears for 

 appendages the antenna; and uiouth-]'arfs ; the prothorax, the first ])air of legs ; the 

 mesothorax, the elytra and middle pair of legs ; the metathorax, the wings and hind 

 pair of leos ; the abdomen, only the genitalia, which are usually concealed in beetles. 

 The prothorax moves with considerable freedom on the mesothorax, and this articula- 

 tion is a character of importance in the se]iaration of the Coleoptera from the 

 Ilvmenoptera, Diptera, and other insects, in which the three divisions of the thorax are 

 more or less firmly united together. These di\-isions, head, prothorax, mesothorax, 

 metathorax, and abdomen, with their appendages, merit much further consideration. 



The head of Coleoptera, both in their larval and adult states, bears the mouth-parts 

 directly forward and slightly downward as in many Carabida?, or directly downward 

 toward the surface on which the insect is standing, as in many ChrysomeliiliT?. Later- 

 ally the head of the adult beetle bears compound ej-es, usually large, and the antenure 

 are generally jnst in front of the eyes. "With few exceptions, among wliich may be 

 mentioned certain Dermestida?, ocelli are absent in the imagos of Coleoptera ; the com- 

 pound eyes are absent or functionless only in a very few cave-inhabiting species. In 

 the larvre, where compound eyes fail, there are often ocelli — from one to seven, 

 usually six, on each side. 



The antenn.T, which are not only organs of touch, but much more olfactory organs, 

 present considerable diversity in form in adult beetles. Often these organs are better 

 developed on the male than on the female, becoming marked secondary sexual char- 

 acters ; this is especially tlie case with the lamelliform antennse of some of the species 

 of ScarabajidiP. In certain families the antennre are not very conspicuous, and can be 

 hidden in grooves, as in the Elateridte ; in other families, as in the Cerambyeidre, the 

 antennse are jirominent organs, often, in the last mentioned family, exceeding the 

 length of the insect, in some species double or treble its length. In a few families, as 

 in the Seolytidie, which have very small antennre, important generic characters are 

 found in these organs. The antennae of beetles may have from two to thirty-four 

 joints, but eleven is the usual number. The anteima^ of most beetle larvse liave but 

 four joints ; rarely they have five, three, or two joints, and in certain cases they are 

 represented only bv a very small inarticulate tubercle. 



Beetles have, without exception, biting or chewing mouth-parts. More or less 

 concealed beneath a well-developed labrum, itself articulated to the epistoma or cl}- 

 peus, is a pair of chitinous mandibles. In the males of Lucanus the mandibles attain 



