122 GRAMMAR OF ENTOMOLOGY. 



membrane, which is upheld and moved by various 

 strong nervures, traversing it in various directions : 

 in the fly, these fore wings alone perform the office 

 of flight ; in the bee, they have the assistance of 

 a second similar pair : a portion at the base of 

 membranaceous wings is called the winglet 

 {alula). 



438. Crustaceous fore wings (jproalce crustacece) 

 are composed of a hard, brittle substance, in- 

 capable of being bent or folded without injury ; 

 incapable also of being used in flight, and serving 

 only as a protecting cover to the more delicate 

 hind wings : the fore wings possess this character 

 in all beetles ; and in descriptions are usually 

 called wing-cases (elytra). 



439. Leathery fore wings (proalce coriacece) 

 are composed of a tough, leathery substance, 

 which will bend readily without breaking, but 

 which never folds naturally ; such wings are 

 seldom of much service in flight, yet are occa- 

 sionally used for that purpose : they have this 

 character in the locust. 



440. Half-leathery fore wings {proalce semi- 

 coriacece) are when they have the basal portion 

 of the leathery substance, described in the last 

 paragraph, and the apical portion, membranaceous 

 and transparent : plant-bugs have this kind of 

 fore wings, 



441. Reticulated fore wings {proalce Micu- 

 latm) are covered by an infinity of nervures 



