CHAPTEE XVII 



INSECTA {continued) 



Order II. ; CoLEOPTBRA (Beetles) 



General THEColeoptera, or "sheath-winged" insects, all have 



Character- four wings, but the front pair is modified to form 



istics. horny protective sheaths, or elytra, which fit exactly 



over the upper surface of the body, showing only the tip of 



the abdomen, and 

 completely cover- 

 ing the hind pair 

 of membranous 

 wings which are 

 used in flying. 

 These wings, in 

 beetles with 

 strong flight, are 

 much larger than 

 the elytra, and 

 when not in use 

 they are creased 

 and folded both 

 longitudinally 

 and transversely 

 so that they fit 

 in below the 

 elytra. 



The mouth- 

 parts are modified for biting, there being very well developed 

 mandibles. The central part of the lower lip is not divided 

 as it is in the Orthoptera (Fig. 139). The insects undergo 



242 



Fig. 168.— The SUver Water Beetle (HydropMlus 

 piceus), with the second pair of wings extended. 

 (Drawn from dead specimen.) 



e, Elytra ; d, triangular plate on the last joint of the tarsus, 

 characteristic of the male. 



