92 Annals Entomological Society of America [Vol. VI, 



supposed that this important feature would also hold true, but 

 this appears not to be the case. Instead, the tracheas arise 

 from two main trunks, the most anterior of which gives rise to 

 costa, subcosta, radius and media, while the other furnishes the 

 origin of cubitus and the anals. 



The two trunks come from the thorax at different angles, 

 and so far as has been observed, are never united (Fig. 21). 

 This does not prove, to be sure, that the connection never 

 occurs, but it would seem that in the study of a very large 

 number of nymphal wings the connection would sometimes 

 have appeared if it were present. On the contrary, the study 

 of a long series of wings of many genera and species seems to 

 show that in this particular family the original hypothetical 

 type of two main trunks has been preserved and that in this 

 respect at least, the Membracidse can be said to be the most 

 generalized of the Hemiptera, being more conservative in this 

 particular than even the Cicada. ■''^ 



Marginal Veins 



The scalloped appearance given to the venation by the 

 marginal vein inside the membrane, is characteristic. The 

 extremities of the longitudinal veins are connected by strong 

 regular veins which form a smooth edge for the veined portion 

 of the wing (Fig. 1). The origin of this structure is explained 

 by the manner in which the ends of the longitudinal tracheae 

 branch and overlap when they reach the region under consider- 

 ation (Fig. 22). Since the reduction of the wing has left at the 

 tip branches of radius two-plus-three, radius four-plus-five, 

 media one-plus-two, media three-plus-four and cubitus one- 

 plus-two which have not entirely coalesced, it is natural that 

 these tracheae, which have probably in the wing of past times 

 represented separate veins, should remain more or less distinct. 

 This has happened, and the wing tip shows that these tracheae 

 tend to pull apart and run along the marginal lines (Fig. 23). 

 It seems rather remarkable that any of these tracheae should 

 ever actually turn backward, but such is the case. The normal 

 method is as follows: subcosta continues along the cephalic 

 margin to the extreme tip of the wing; Ri unites with subcosta 



34. Comstock and Needham state, "The conservative Hemiptera that 

 retain most perfectly the fashions of ancient times so far at least as concerns the 

 venation of the wings, are the cicadas." — Wings of Insects, p. 243. 



