202 
SYSTEMATIC ARRANGEMENT. 
The upper wings are hard and horny throughout 
their whole extent, forming a protecting cover to 
the under pair, and arc therefore named elytra. From 
this circumstance also the name of the order is de- 
rived, being compounded of xo Xsog, a sheath, and trreg a, 
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 the 
only kinds with which the larvae are furnished. The 
prothorax is very freely articulated to the succeeding 
segment, and the pronotum is so large as to form a 
considerable part of the dorsal surface. On each 
side of the pronotum, in the carabideous and aquatic 
beetles, there is a distinct corneous scale from which 
the muscles of the coxee originate, called the smaller 
or anterior shoulder-blade ( omium ) by Burmeister. 
The horns and other prominences frequently rising 
from the pro thoracic case are mere processes or in- 
tegral portions of its crust, except in one instance, 
the Harlequin beetle ( Acrocinus longimanus ), which 
has a large moveable spine on each side. The only 
portion of the mesotliorax appearing on the surface, 
is the small triangle named the scutellum ; its whole 
volume, indeed, is comparatively contracted, owing, 
no doubt, to the elytra which it supports not being 
