20 SOME ASPECTS OF MORPHOLOGY 



insect wing (Fig. 9). Each vein bifurcates into an anterior or 

 convex branch ( + ), and a posterior or concave branch (or 

 sector, — ). The concave subcostal vein, he beUeves, represents the 

 posterior branch of the costal, while his conception of the radius 

 does not differ from that of Comstock. The division of the media 

 into an anterior convex branch (MA) and a posterior concave 

 branch (MP) is a conclusion of prime importance. The logical 

 deduction to be drawn is that the media of Comstock, being a 

 concave vein, is the counterpart of the posterior media (MP) of 

 Lameere. This interpretation, however, was not advanced by 

 Lameere, who believed that MP is wanting in Holometabola with 

 the exception of a rudiment which had been previously regarded 

 by Tillyard (1919) as representing M5. Since, however, M5 

 according to Tillyard (1925) is convex in character, Lameere's 

 homology is improbable. It needs to be pointed out, however, 

 that Tillyard stated definitely in his earlier writings that M5 is a 

 concave vein and that Lameere based his conclusions upon this 

 assertion.^ With regard to the cubitus, Lameere's anterior 

 branch corresponds with Cuj (convex), and his posterior branch 

 with Cug (concave). His interpretation of the anal veins differs 

 from those of his predecessors in that he claims that two bifurcate 

 veins are present in the anal area. This conclusion can scarcely 

 be reconciled with the more usually accepted interpretation 

 (Fig. 7), and the theoretical assumption, that every wing vein 

 conforms to a regular basic system, remains to be proved. 



When Lameere's hypothetical scheme is applied to recent 

 insects several important modifications become apparent, more 

 especially with regard to the media. It would seem that this 

 vein is only rarely represented by both of its branches — MA and 

 MP. This condition is retained among Ephemeroptera and is 

 certainly present in the Orthoptera. A comparative study of the 

 venation of both recent and fossil representatives of the last- 



^ The oblique vein M5 is a characteristic feature of the orders forming the 

 Panorpoid Complex, and is evident in their Upper Permian fossil representatives 

 also. Tillyard (1919) regarded it as a basal concave vein connecting M with 

 Cui to form the cubito-median Y-vein. In a later paper (1925) the results 

 of further study led him to conclude that it is little more than a convex strut, 

 which has arisen as a secondary development, in order to provide rigidity to 

 the base of Cu^. 



