580 



THE PANORPOID COMPLEX, 111., 



diverge to run separately to the wing-border (Text-fig. 55?*). 

 This condition is the one found in the hindwing of the well- 

 known atavistic individual of Sthenopis figured by Comstock 

 (15, fig. 337), and also seen in the fossil Archipanorpa (Text- 

 fig. 57) . Further specialisation results in the formation of the 

 complete distal Y-vein, in which the two veins, after fusing, 

 remain in this condition right to the wing-border (Text-fig. 55, 

 e) . This stage is the one visible throughout the family Hepi- 

 aliclae. 



In examining the pupal wing of Eriocrania, no trace of a 

 separate trachea M 4 could be found ( 27) . I therefore made 

 very careful examinations of this area of the pupal wing in 

 the Hepialidae and Cossidae. The result of a large number of 

 dissections proves that trachea M 4 is never present in the 



Text-Fig. 56. 

 Detail from the pupal wing of Xyleutes (fam. Cossidae), to show 

 trachea Mj. in situ, (x 8). 



freshly-turned pupal wing of the Hepialidae, though I have 

 succeeded in finding it once (Text-fig. 5G) in the freshly-turned 

 pupal wing of the Cossid genus Xyleutes. In this case, trachea 

 M 4 was small, but quite distinct, and was bent back in the 

 manner shown in Text-fig. 5G, in correlation with the highly 

 specialised direction of vein M 4 in the imaginal wing. 



In a single pupal wing of Hepialus which he examined, Mac- 

 Gillivray ( 16) also failed to find any trace of trachea M 4 . ft 

 would be easy to jump to the conclusion that the vein M 4 : has 

 been lost altogether in this family, and that the oblique vein 



