THE WINGS OF MEMBRACID^ 



277 



In the hind wings a greater reduction of the tracheation and the vena- 

 tion than is the case in the fore wings has taken place. Figure 280 repre- 



Fig. 2i 



-The tracheation of the hind wing of a nymj)h of Tlielia himaculata 

 (After Funkhouser). 



sents the tracheation of a hind wing of a nymph of Thelia bimaculata; 

 and Figure 281, the venation of a hind wing of the adult of this species. 



A discussion of each of the principal veins separately will indicate more 

 completely the reasons for the conclusions regarding their identity. 



The costa. — There is a great reduction of the costa in this family. In 

 the wings of nymphs the costal trachea sometimes persists, but it is more 

 often lacking. Figure 282 represents the tracheation of a fore wing of a 



Fig. 281. — The venation of a hind wing of Thelia bimaculata (After Funkhouser). 



nymph of Thelia bimaculata in which there was a distinct costal trachea; 

 but it extends only a short distance into that part of the wing which becomes 

 the wing of the adult. In a fore wing of a nymph of Ceresa borealis 



