THE WINGS OF LEPIDOPTERA 



329 



In the fore wings, veins Cu and ist A coalesce at the base, where they 

 He at the bottom of the cubito-anal sulcus (Fig. 334)- From the point of 

 separation of the two veins, the cubitus extends at first in an oblique direc- 

 tion, appearing like a cross- vein; when it has nearly reached the media, it 

 bends abruptly and extends longitudinally to the outer margin of the wing. 



The cubitus is joined to the media by a short vein, which appears to 

 be homologous with the posterior arculus of the Trichoptera; but which, as 

 it contains a branch of the median trachea, may be the base of vein M4, the 

 more distal part of vein M4 coalescing with vein Cu. I have been unable to 

 find anything corresponding to the posterior arculus in the Frenats; for 



Fig. 337. — Venation of an abnonnal individual of Sthenopis. 



this reason it seems probable to me that it has not been developed in the 

 Lepdioptera; and that what appears to be the posterior arculus in the 

 hepialids is a section of vein M4. 



Lest the similarity of the course of vein Cu in the fore wing of the 

 hepialids to that of this vein in the Trichoptera be given undue weight, I 

 call attention to the fact that in the fore wing of the Cicada (Fig. 269) 

 where veins Cu and ist A are crowded together in the cubito-anal sulcus 

 and coalesce there, the free part of vein Cu follows a similar course. 



There are three anal veins in the fore wings of the hepialids. The first 

 anal vein is aligned with vein Cu + ist A and extends a short distance in 

 the cubito-anal fold, but the distal part of it has atrophied. No distinct 

 anal furrow exists in any of the hepialids that I have studied; there is 



