WINGS OF INSECTS, AND THEIR CLASSIFICATION. 41 



"What then is a beetle ?" 



The name of the order to which beetles belong will 

 partly answer this question. Coleoptera, from icoXtoc 

 (Koleos), a sheath, irrtpov (Pteron), a wing. A beetle 

 may be described as a four-winged insect, whose first 

 pair of wings, being thickened to a horny or leathery 

 consistence, form a covering or " sheath" to the hind 

 pair. This is the most conspicuous character of the 

 order, and one by which nearly all beetles may at once 

 be recognised. The common cockchafer will .serve as a 

 familiar example, for there are few persons who do not 

 know this insect. There are even perhaps few who have 

 not watched it raise its brown wing-cases, and, spreading 

 them apart, unfold the large and beautiful wings, delicate 

 glistening membranes, extended and supported by strong 

 nerves, which are to them what the spars of a ship are 

 to the sails. But no ship's spars are so jointed as these 

 nerves no sails so reefed as these membranes; .the 

 captain of no ship could fling out his sails, let the 

 wind blow which way it will, and, helmless, trust 

 them to bear him to his haven. Yet this can our 

 little beetle do. And this he does, let it be observed, 

 with a single pair of wings, whilst the other pair, 

 thickened, and utterly useless in flight, unless indeed 

 they serve to guide it, might seem to be even a 

 hindrance to his motions. Now, certainly, we should 

 not have expected that beetles, perhaps on the whole 

 the most ponderous of flying insects, should thus 

 have been deprived of half their support by such a 

 modification of the very organs of locomotion as the 

 conversion of one pair of wings into a sheath for the other. 



How then is this loss compensated ? In the beetles the 

 hind wings (which in most other orders of insects are con- 



