644 



THE PANORPOID COMPLEX. 111., 



anal veins is to be seen in the forewing of Trictena labyrinthica 

 (Text-fig. 79), in which this loop is completed by the interven- 

 tion of the interanal cross- vein ia\. 



The conclusions to be drawn from the above are, I think, that, 

 on the whole, the freshly-turned pupa gives us the most primitive 

 condition of the wing-tracheation ; that the tracheation of the 

 imaginal wing shows a considerable amount of specialisation; 

 and that the development of trachea? M 5 and M 4 , the former late 

 in pupal life, the latter occasionally at metamorphosis, may well 

 represent the late appearance of trachea? which are in process of 

 being lost altogether. 



We may now turn our attention to the genus Leto, of which 

 I was able to dissect several pupae obtained for me by Mr. Luke 

 Gallard. These pupa? are of very large size, some being four 

 inches long, so that their dissection is a fairly easy matter, and 

 the tracheation can be studied under a low power. 



Text-fig. 80 shows the bases of the wings in an early pupa of 

 Leto staceyi Scott, dissected off and floated out upon a glass slide 

 in water. If these be compared with Chaiagia (Text-fig. 77) it 

 will be seen that there are some important differences, as fol- 

 lows : — 



Text-Fig.80. 

 Basal portion of tracheation of a, forewing, b, hindwing, in the freshly 

 formed pupa of Leto staceyi Scott, (x 3). Lettering as on p. 535. 



