366 



THE STUDY OF INSECTS. 



closely resemble those of the Hesperiidae. But the Giant 

 Skippers exhibit a very peculiar specialization of wing struc- 

 ture in the male sex. Here the two branches of vein VII of 

 the fore wings separate from each other and from the cross- 

 vein connecting them with, vein V 3 , near the base of the 

 wing (Fig. 446). In this sex this cross-vein, the branches of 



Fig. 447. — Wings of Megatkymus 

 cofaqui, female. 



VII2 



XI JX. 



Fig. 446. — Wings of Megatkymus yucca, male. 



vein VII, and vein IX are all very stout. The strengthening 

 of these veins is evidently a specialization that increases the 

 power of flight of this sex. For these stout veins must aid 

 in depressing the hind wings during the downward stroke of 

 the wings, as the hind wing is overlapped by that part of the 

 fore wing traversed by these veins. The separation of the 

 branches of vein VII from each other and from the cross- 

 vein, so near the base of the wing, is directly correlated 

 with the strengthening of these veins. In the course of 

 the perfecting of the powers of flight in the male these 



