1913] 



Helicopsyche Molannidce and Leptocerid(E 



71 



that have fused. The alternative interpretations are indicated 

 in Fig. 5c. To decide between these possibihties we should 

 have to find out which fusion took place earlier in the phylo- 

 genetic series and on this question the evidence seems incon- 

 clusive. 



While the purpose of this paper is fulfilled in showing that 

 the modifications of radius may be similarly interpreted in 

 Helicopsyche, the Molannidae, and the Leptoceridas, another 

 instance of similar modifications may be added lest the basal 

 shifting of a distal branch from one main stem to another 

 should seem unlikely in this order. A parallel case is shown in 

 media of the fore wing of Oecetis*. Authors from McLachlan 



Fig. 7. Venation of apical part of fore wing of species of Oecetia. a, Oecetia 

 fumosa. b, Oecetia incerta. c, Oecetia testacea (after McLachlan). 



on agree in saying that media in Oecetis is absolutely simple or 

 unbranched. No one seems to have been disturbed by the 

 fact that on such an interpretation an extra branch would have 

 to be assigned to cubitus. As a matter of fact media is always 

 two branched in Oecetis as it is in most of the other Leptocer- 

 idas. In O. fumosa (Fig. 7a) while there is slight variation in 

 exact position, M3+4 leaves M14.2 at about right angles; it bends 

 sharply and then proceeds to the wing margin. At the latter 

 angle it is joined by the cross vein m-cu which is in line with the 

 distal end of M3+4 so that the resulting deceptive appearance is 

 that of an extra branch on the anterior side of cubitus joined 

 to media by a cross vein which is in reality the base of M3+4. 

 In O. incerta (Fig. 7b) the cross vein m-cu is very short, in some 



*I include here Oecetina Banks and Oecetodes Ulmer. 



