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 effect 

 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 w^hich are on 

 record, we may detect the consequences of heat ; either 



* Introduction to the Modern Classification of Insects, ii. 

 p. 431. 



