1919] Braiin: Wing Structure of Lepidoptera 355 



the course common to Mnemonica and Rhyacophila, if we 

 assume an anastomosis of M and Cii, obliterating the posterior 

 arculus (such as Comstock shows has taken place in a species 

 of Rhyacophila) to have proceeded to the base of the wing. 

 This view is strengthened by the course -of the persistent 

 cubital trachea in the fore wing of a specimen of Nepticula 

 platanella (a comparatively generalized species of its genus) 

 which follows the first anal vein at the base, bending obliquely 

 toward media which it reaches at the point where m.edia bends 

 upward toward radius, then extending longitudinally along the 

 usual course of cubitus. The venation of the hind wing shows 

 an advance over that of the fore wing, even in the most gen- 

 eralized Nepticulidae, in that media and radius coalesce for 

 half their length; this condition, which is brought about by the 

 crossing over of media to radius at the base has been attained 

 in part of the genus Nepticula in the fore wing. 



In the Hepialidce the course of cubitus of the fore wing is 

 the same as it is in the Micropterygidae. In the hind wing Cu 

 is free from 1st A at its base; there is no evidence from pupal 

 wings or adult forms to indicate how this condition may have 

 been derived from one in which Cu follows the same course as 

 in the fore wing. 



The coalescence of the tips of two branches of the third 

 anal vein with the tip of the second anal vein of the fore wing 

 is a character common to both the more generalized Trichoptera 

 and Micropterygidae. The second branch 6i the third anal vein 

 tends to disappear very early in phylogeny, although the third 

 anal trachea is often forked in the pupa. Even in the most 

 primitive Micropterygidae, as Sabatinca, this coalescence of 

 veins is shown in one species and not in the other. The second 

 branch of the third anal vein is but faintly shown in Epi- 

 martyria (Fig. 1). In Scoliaula of the Nepticulidae, there is a 

 faint indication of a second branch of the third anal vein, 

 represented merely by a broad slight thickening of the wing 

 membrane, but neither it nor the first branch continue far 

 enough to unite with the second anal vein. In Hepialidae, the 

 second branch of the third anal vein shows no tendency to 

 unite with the first branch, but runs close to the margin of the 

 wing. Among the Frenatae, the condition of the branches of 

 the third anal vein in Prionoxystus is similar to that in Hepialidae. 



