282 PTILOTA : IMAGO — EXTERNAL ANATOMY. 



some kind of support, which is afforded by the scutellum. 

 They are thus circumstanced in beetles, and in the hetero- 

 pterous Hemipteraj but in the tribes in which tegmina are 

 present, the scutelhim is not a prominent organ; they are 

 therefore more essentially organs of flight than elytra or he- 

 melytra, which we now proceed to describe ; commencing 

 with the former, as being intermediate in their formation be- 

 tween tegmina and elytra. 



(c) The Hemelytra (see fig. 131, 132, hemelytron of Hete- 

 rog aster urticce). — Under this name, Latreille described 

 {Hist. Nat. Crust. &c., ii. p. 164) the anterior organs of flight 

 of the Cimicidce, or heteropterous Hemiptera, the basal por- 

 tion of which is thick, opaque, and coriaceous, and the ter- 

 minal part thin and membranous; the transition between 

 the two kinds of membrane not being gradual, but sud- 

 den. The wings covered by these limbs are membranous, 

 and of the size of the hemelytra. On examining an heme- 

 l}i;ron, the three areas of which wings and tegmina are com- 

 posed are here distinct ; but they do not extend beyond the 

 corium (or basal coriaceous part) ; hence the apical membrane 

 seems a piece added to the ordinary structure ; sometimes 

 being, in fact, absent, although the corium is distinct. In 

 some instances, the entire hemel}i;ra are formed of membrane, 

 or rather the substance of the corium is so much diminished 

 that it resembles the apical membrane. When at rest, the 

 apical membrane of one hemelytron folds upon that of the 

 other, and the position is usually horizontal. As to their 

 neuration, the basal corium, as may be conceived from its si- 

 milarity to the substance of the elytra, is generally almost 

 destitute of nerves ; but the apical membrane differs in hav- 

 ing more or less numerous nerves, which serve for the dis- 

 tinctions of genera and sub-genera. 



(d) Elytra (see fig. 133). — This is the name given to the 

 hard scaly or horny wing-covers, or anterior wings of beetles ; 



