164 



THE WINGS OF NEUROPTERA 



when the data presented by the Sialidae, Hemerobiidse, and Osmyhd^ are 

 considered. 



If the suppression of the dichotomy of the sector were taking place by 

 the coalescence of veins R4 and R5 one would expect to find the incomplete 



' rca ' 



Fig. 159. — Wings of Palpares ceschnoides var. libelluloides . 



stages of this coalescence, if they still exist, in the more generalized wings 

 of this family, and to find it completely attained in the most specialized 

 wings. The fact is the radial cuneate area is largest in the more highly 

 modified wings of the Myrmelionidae, as in the Acanthaclisinae (Fig. 156) 

 and in the Palparinffi (Fig. 159), while it is lacking only in wings that are 

 much less modified (Fig. 160). 



That the radial cuneate area is a secondary development is indicated by 

 the fact that in the wings where it is the largest similar areas have been 

 developed in other parts of the wing, as in area behind the serial vein Cui 

 & M3+4 of the fore wing of Palpares (Fig. 159). In this connection com- 

 pare the splitting back of the tip of vein R5 in the myrmeleonid wings 

 represented by Figure 158 with similar splitting back of the tips of acces- 

 sory veins near the apex of the same wings. 



The secondary nature of the radial cuneate area is also shown in the 

 Hemerobiidse. In the generalized Hemerohius humuli (Fig. 175) there is 

 little if any indication of a greater expansion of the tip of vein R5 than there 

 is of other branches of the radial sector; but in the highly specialized 

 Megalomus mcestus (Fig. 178, r c a) the radial cuneate area is very prom- 

 inent. 



