45 



genus Delphax, the majority of which^ in our English 

 species, have the upper wings not covering more than 

 one half of the abdomen, — the terminal membrane 

 being deficient, as well as the hind wings. In certain 

 seasons, however, especially hot ones, the wings are 

 fully developed*". Mr. Curtis has indeed formed the 

 undeveloped specimens into a different genus, Crio- 

 morphus. 



Although the result of a more stimulating sun may 

 be often neutralized by that of isolation (which, as we 

 shall hereafter see, is a resistless agent, amongst a host 

 of species, in weakening, and frequently rendering abor- 

 tive, the powers of flight) ; yet heat, when freed from 

 counter influences, may be traced in its permanent efiect 

 on the alary system of insects, no less than when tem- 

 porarily applied. The consideration of this, however, 

 belongs strictly to the preceding pages, and we will not 

 therefore discuss it here. The common Bed-bug {Cimex 

 lectularius, Linn.) is almost invariably apterous, or with 

 very short rudimental hemelytra; yet Scopoli {Ent. 

 Cam. p. 354) mentions its occurrence with perfect 

 wings. Fallen, also, and Latreille, state that it has 

 been found winged ; whilst Westwood remarks that it 

 has been reported as occasionally winged in the East 

 Indies ; and it would seem extremely probable that, in 

 these examples, as in numerous others which are on 

 record, we may detect the consequences of heat; either 



* Introduction to the Modern Classification of Insects, ii. 

 p. 431. 



