202 SYSTEMATIC ARRANGEMENT. 



The upper wings are hard and horny throughout 

 their whole extent, forming a protecting cover to 

 the under pair, and are therefore named elytra. From 

 this circumstance also the name of the order is de- 

 rived, heing compounded of jcoXso;, a sheath, and Trrsca, 

 wings. Where the elytra, or wing-cases, meet, they 

 form a straight sutural line along the back. The 

 under wings, which are the true organs of flight, are 

 membranous and transparent ; when at rest they are 

 folded transversely. The mouth is constructed for 

 mastication, and all the parts are very highly de- 

 veloped. Stemmatic eyes have not been observed 

 in the perfect insect, except in the genera Ontho 

 phagus, Omalium, and Paussus ; but they are th 

 only kinds with which the larvse are furnished. Th 

 pro thorax is very freely articulated to the succeedin 

 segment, and the pronotum is so large as to form 

 considerable part of the dorsal surface. On eac 

 side of the pronotum, in the carabideous and aquati 

 beetles, there is a distinct corneous scale from whic 

 the muscles of the coxae originate, called the smalle 

 or anterior shoulder-blade (omium) by Burmeiste 

 The horns and other prominences frequently risin 

 from the prothoracic case are mere processes or in 

 tegral portions of its crust, except in one instance 

 the Harlequin beetle (Acrocinus longimanus), whic 

 has a large moveable spine on each side. The only 

 portion of the mesothorax appearing on the surface, 

 is the small triangle named the scutellum ; its whole 

 volume, indeed, is comparatively contracted, owing, 

 uo doubt, to the elytra which it supports not beingj 



