EXTERNAL ANATOMY OF INSECTS. 617 



they are usually obliquely truncated, than at the base ; 

 but in Plea Leach they are obtusangular, with the angle 

 in the sutural margin ; in Nolonecta, on the contrary, an 

 obtusangular sinus distinguishes that part ; in Naucoris 

 they are curvilinear and every where of equal width ; in 

 ~Rana.tr a they are linear and straight; in Aradus they 

 are oblong, usually with an external lobe or dilatation at 

 their base: a remarkable instance of the intention of this 

 is observable in a nondescript Brazilian species, in which 

 the head, prothorax, and abdomen, are edged with a 

 number of broad foliaceous appendages ; if the base of 

 the hemelytrum had not been furnished with a similar 

 appendage, the symmetry of the whole body would have 

 been destroyed by the hiatus between the prothorax and 

 abdomen, as may be seen by removing the hemelytra ; but 

 by this compensating contrivance of Providence, the gap 

 is filled, the above lobe fitting exactly into it. 



6. The neuration of these organs will not occupyus long, 

 since the corium or harder part, though in some species 

 there are traces of nervures, is often without them. Those 

 of the cucullated species of Tingis resemble many tegmina 

 in being ornamented by them with a kind of network, 

 which looks like the finest lace; in several Lygcei, Edessa, 

 and some Reduvii, there are a few diverging longitudinal 

 nervures which occasionally by a ramification here and 

 there form an areolet a , but there are seldom any tra- 

 versing nervures. The Apical Area is usually most di- 

 stinguished by nervures, in some forming several areolets, 

 as in Aradus, in others running parallel to each other, 

 nearly to the end of this area, as in Belostoma grandis, 



■'■ Plate XXVII [. Fig. 23. 



