CLASS INSECTA. 17 



opinion seem to replace the two wings which are wanting. 

 They are named balancers ; other insects with two wings, 

 and some of the most extraordinary, have also two balancers, 

 but situated at the anterior extremity of the thorax, and 

 which we shall name, to distinguish them from the other, 

 prehalancers. Above the balancers, is a small membranous 

 scale, formed of two pieces united by one of the edges, and 

 resembling the two lids of a bivalve shell ; this is the wing- 

 let. Some aquatic coleoptera have these below their elytra, 

 and inserted at the base of the latter. 



Many insects, such as the May-bugs, cantharides, &c., 

 have, instead of the two upper or anterior wings, two kinds 

 of scales, more or less thick, and more or less solid. They 

 are opake, open and shut, and the wings are folded trans- 

 versely under them in a state of repose. These sort of cases 

 have received the denomination of elytra.* The insects 

 which are provided with these, are called coleoptera^ or 

 insects with cases ; these pieces are never wanting in this 

 order, but it is not always so with the wings. In other 

 insects, the extremity of these scales is altogether membra- 

 nous like the wings ; they are then named half cases, or 

 hemelTjtra. 



The shield is a piece usually triangular, situated on the 

 back of the mesothorax, between the attachments of the 

 elytra, or the wings ; it is sometimes very large, and then 

 covers the greater part of the upper portion of the abdomen. 

 Divers hymenoptera have behind it, on the metathorax, a 

 small space which is named hinder shield, or false shield. 



* See, for their chemical composition, a memoir, already cited, of 

 M. Odier, inserted in the Collection of Memoirs of the Society of Natural 

 History in Paris, and the article Insects in the fore-mentioned " Diet. 

 Classique d'Hist. Nat." 



VOL. XIV. C 



