352 Annals Entomological Society of America [Vol. XII, 



(a) Venation. 



Certain striking characteristics of venation are held in 

 common by the more generalized Trichoptera, such as Rhya- 

 cophila and by the more generalized of the Micropterygidas, 

 These characteristics have been enumerated by Comstock 

 (The Wings of Insects, 1918, p. 317). In fact, the resemblance 

 is so close that the only essential difference to be noted is that 

 in Micropterygidae media of both wings has been reduced tO' 

 a three-branched condition, apparently by the coalescence 

 of Mz and Mi, while in Rhyacophila Mz and -Mi are separate in 

 the fore wing, although united in the hind wing. This identity 

 of characteristics is shared by no insect not belonging to 

 Micropterygidee or Trichoptera. That it is possible to trace 

 the modification of these trichopterous characters and their 

 transformation into what are commonly recognized as the usual 

 lepidopterous characters, such as are found in the frenate 

 Lepidoptera, will be shown from evidence derived from the 

 Micropterygidfe themselves, the Nepticulid^, the more primitive 

 frenate Lepidoptera, and the Hepialidae. 



The forms for study of venation in the more primitive 

 Lepidoptera have been chosen because they show, besides the 

 preservation of media, certain characters — such as the costal 

 spines on the hind wing, absence of frenulum in the female, 

 fixed hairs on the wings and folded maxillary palpi — all of 

 which indicate a generalized condition. 



In the Micropterygidas veins Cii and 1st A of both fore and 

 hind wing coalesce at the base of the wing; from their point 

 of separation Cu extends obliquely across the wing toward 

 media, then bends and extends longitudinally to the margin. 

 In the hind wing, the point of separation of Cu and 1st A is 

 nearer the base than in the fore wing. A short cross-vein, the 

 posterior arculus, connects media with the longitudinal part 

 of Cu, forming with the base of media, a serial vein in the 

 fore wing. The presence of this condition in Mnemonica 

 a-hd in Rhyacophila is pointed out by Comstock in his book 

 "The Wings of Insects," where wings of both are figured 

 together with figures of the tracheation in the base of the 

 wings of Mnemonica, which confirm the homologies of the veins 

 as determined from a study of adults. In so far as published 

 figures of other genera of the Micropterygidae show the details 



