652 THE PAKORPOID COMPLEX, 111., 



vein in this case is the cross-vein m-cu, then it must follow that 

 Cm is itself a forked vein; for neither of the branches of the 

 terminal fork can belong to M, on this supposition. I do not 

 think that anybody will accept this alternative, and I am unable 

 to suggest any other possible explanation. 



The position seems to be this : — that the evidence for the exist- 

 ence of M 4 in the Lepidoptera is not conclusive, but may be 

 accepted provisionally upon the balance of probabilities. The 

 evidence in favour of the cross-vein theory is as complete as it 

 is ever likely to be. But those who support the theory that M 4 

 is present have all the possibilities of new evidence to count 

 upon, both from further dissections of pupal wings, and from 

 new fossil discoveries which may reinforce the evidence of 

 Archipanorpa and Sthenopis. 



In my researches upon the Jugo-frenata (27), I used the nota- 

 tion m-cu for the vein which I here call M 4 . The evidence 

 from the pupal wings of Eriocrania, on which the notation of 

 that paper is based, is against the presence of M 4j seeing that 

 there is no trachea preceding this vein in the pupal wing. The 

 alteration in the present paper is due to the consideration of 

 much evidence from outside the Jugo-frenata. I should like 

 also to point out that, in both fore and hindwings of the Microp- 

 terygidae and Mnesarchaeidae, and also in the hindwings of the 

 Eriocraniidae, the position of this vein is such that it is much 

 more likely to be M 4 than m-cu, seeing that the latter, in the 

 Order Trichoptera, is situated either at, or a little basad from, 

 the secondary median fork, mf' . Only in the forewings of the 

 Eriocraniidae is the position of this vein such that it would 

 naturally be taken for m-cu. 



A slight correction is necessary in Text-figs. 5 and 6 of the 

 paper here referred to, (27) . The dotted line passing trans- 

 versely from the secondary radial fork rf\ to the media below 

 it, should be omitted, since there is no cross-vein in this position. 



Throughout Section xiv., the lettering of the Text-figures has 

 been made on the view that M 4 is present, not only in the 

 Hepialidae, but also in the rest of the Homoneura, and through- 

 out the Heteroneura. The evidence from the pupal wing of 

 Xyleutes (Text-fig. 50) favours this view for the Heteroneura; 

 but, even without that, there can be no doubt that the vein 

 which I have labelled M 4 in the Prototheoridae (Text-fig. 83) 

 is the homologue of the vein labelled M 4 in the Heteroneura. 



