EY R. ,1. TlLLTARD. 



549 



Ca ^ Cu lb ~ Cu u 

 Text-Fig.38. 

 Venation of fore wing of Archetype of the Panorpoid Complex as worked 

 out in this Part. (See also Text-fig. 111). Lettering as on p. 535. 

 Note especially the fusion of Ms with Cu] to form the eubito- 

 median Y-vein. 



belonging to the Order Protomeeoptera, I described a well- 

 developed" costal vein (5), and, in the fossil genus Aristopsyche 

 of the Order Paratrichoptera (28), I also described a much- 

 shortened costal vein near the base of the wing. Besides these, 

 a strongly developed costal trachea may be found running along 

 the anterior marginal vein in the imaginal wings of many Tri- 

 choptera and Diptera. 



Further study of the fossils above mentioned has convinced me 

 that the veins which I originally described as the costa are, in 

 reality, only branches of Sc. In Arclii pernor pa (Text-fig. 64), 

 the origin of this vein is missing. But it is strongly concave, like 

 Sc below it; whereas a true costal vein should certainly be con- 

 vex. In Aristopsyche, I have succeeded in tracing the supposed 

 vein C back to a definite origin on Sc; so that this vein also 

 must be considered as a shortened basal branch of the latter. 



As it seems very likely that the marginal vein of Trichoptera 

 and Diptera may be a secondary development, due to strength- 

 ening of the anterior border of the wing, 1 have decided to omit 

 the question of the presence or absence of a true costal vein from 

 the evidence used in constructing the Archetype. It seems, 

 however, very unlikely that any tine costal vein, distinct from 

 the anterior border of the wing, was ever present in any Panor- 

 poid type,' seeing that such a vein is absent from almost all 

 known insect wing's. 



