THE WINGS OF NEUROPTERA 



159 



In Sisyra flavicornis (Fig. 152) definitive accessory veins have not been 

 developed upon the radial sector, although there are marginal accessory 

 veins upon its branches. In each wing the sector is four-branched. These 



Fig. I54-- 



-Base of a hind wing of Hemerobius 

 hitmuli. 



branches are doubtless \'eins R-:, R3, R4, and R5. The dichotomy of the 

 sector has been suppressed by the splitting back of vein R5. Two stages in 

 this splitting process, are represented by the two wings, it having been 

 carried much farther in the fore wing than in the hind wing. Attention is 

 called to the wings of this insect to show that the veins that are split back 

 in the hemerobiid group of families are primitive branches of the radial 

 sector and not accessory veins. 



In the wings of Hemerobius humuli (Fig. 153), the splitting back of 

 branches of the radial sector is can'ied much farther than in Sisyra. In the 



Fig. I55-- 



-Tracheation of the wings of a pupa 

 of Hemerobius liumuli. 



hind wings of this species there are only four definitive branches of the 

 radial sector, although there are many marginal accessory veins. The 



