CHAPTER XX 

 ORDER COLEOPTERA* 



The Beetles 



The winged members of this order have four wings; but the wings of the 

 first pair are greatly thickened, forming "wing-covers" or elytra, beneath 

 which the membranous hind wings are folded when at rest. The elytra meet 

 in a straight line along the middle of the back and serve as armor, protecting 

 that part of the body which they cover. The mouth-parts are formed for 

 chewing. The metamorphosis is complete. 



The order Coleoptera includes only the beetles. 

 These insects can be readily distinguished from all 

 others except the earwigs by the structure of the 

 fore wings, these being horny, veinless " wing- 

 covers " or elytra, which meet in a straight line 

 along the middle of the back (Fig. 210); and they 

 differ from earwigs in lacking pincer-like ap- 

 pendages at the caudal end of the body. Beetles 

 also differ from earwigs in having a complete 

 metamorphosis. FlG - 2I °- 



The hind wings are membranous, and in most species very efficient 

 organs of flight. But in some of the pre-eminently running beetles the 

 hind wings are wanting, and the elytra serve only as a protection to the 

 abdomen. With some of these insects the elytra are even grown together 

 where they meet on the middle line of the back; and in some of the 

 Meloidae the elytra do not meet in a straight line. 



The venation of the wings of the Coleoptera has become greatly 

 modified, and, consequently, the determination of the homologies of the 

 wing veins is a difficult matter. The transformation of the fore wings 

 into elytra has resulted in a great reduction of their venation; and the 

 foldings of the hind wings interrupt the veins and cause distortions in 

 their courses. 



The different mouth-parts are very evenly developed; we do not find 

 some of them greatly enlarged at the expense of others, as in several 

 other orders of insects. The upper lip, or labrum, is usually distinct; the 

 mandibles are powerful jaws fitted either for seizing prey or for gnawing; 

 the maxillae are also well developed and are quite complicated, consisting 

 of several distinct pieces; the maxillary palpi are usually prominent; 

 and the lower lip, or labium, is also well developed and complicated, con- 

 sisting of several parts and bearing prominent labial palpi. 



The larvas are commonly called grubs. They are usually furnished 

 with six thoracic legs, and often with a single proleg at the caudal end of 

 the body; some, however, as the larvae of the snout-beetles, are entirely 

 * Coleoptera: coleos (/coXeos), a sheath; pteron (wrepov), a wing. 



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