WING CASES. 381 



which it quickly unfolds, puts into motion, and 

 then flies away. The two thick and horny covers 

 for these delicate organs are called elytra, or 

 " wing-cases." They are really the first pair 

 of wings, much thickened ; and their use is to 

 protect the delicate membranous wings of the 

 hinder pair, beneath them. When the insect 

 flies, they open like a box-lid, and are carried out 

 of the way of the other wings ; when the insect 

 rests it carefully folds up its other wings, and then 

 these close over them, and preserve them from all 

 injury. As the insects in which they are found 

 frequent places of danger, burrow underground, 

 or take up their abode under stones, it is manifest 

 how admirable a contrivance this is for such pur- 

 poses, and how efficiently the fragile wings will 

 be covered and protected by such shields. The 

 first pair of wings is sometimes thickened to the 

 consistence of parchment as a cover to the other 

 wings ; and they are then called tegmina, or 

 " wing-covers." 



There are two other circumstances in connexion 

 with this part of our subject, which deserve 

 noticing. If the reader will take into his hand 

 a large blow-fly, and carefully examine its body 



