572 



THE PANORPOID COMPLEX, 111., 



Text-Fig. 47. 

 Comparison of the venation of a Megalopteron (Aus/tosialis ignicollis 

 Till., fig. a) with a Trichopteron ( Rhyacophila dorsalis Curtis, 

 fig.$), forewings only, to show the similar structure of the cubitus. 

 Note the strong fusion of Mi_4 with Cui in Austrosiahs, and the 

 double fusion of the anal veins in Rhyacophila. Lettering as on 

 p. 535. 



But, knowing the truth as regards Austrosialis, we can compare 

 its imaginal venation with that of Rhyacophila. We then find 

 that the two venational types agree in practically every detail 

 of the courses and branchings of their main veins, and only 

 differ in the number and arrangement of their cross-veins and 

 veinlets, and in the fact that the Trichopteron shows a high 

 specialisation of the anal area, (viz. the looping-up of the three 

 anal veins), which is absent in the Megalopteron. The corres- 

 pondence between the venations of the hindwings of the two 

 types is even closer, but need not be figured here. There can, 

 I think, be no doubt whatever that the cubitus in the Trichop- 

 tera is three-branched, as in the Megaloptera. 



If, finally, we turn to the Lepidoptera, we find that the 

 cubitus in this Order is of the same type as that seen in the 



