ORGAXIC EVOLUTION 



227 



First, nature has not made the cross veins visibly to 

 differ from the bases of branches, and the angulated and 

 transverse base of a branch may look like a cross vein. It 

 will help in settling their identity to note carefully the type 



11 



FIG. 139. The venation of the wings of a series of cranenies. /, Limnophila; 

 2, Cylindrotoma; 3, Liogma; 4, Anisomera; 5, Ctenophora; 6, Dolichopeza; 

 7, Acyphona;S, Ula; 9, Mongoma; 10, Oropeza; //, Erioptera. 



of branching of the veins. The radial sector springs from 

 the posterior side of the radial stem, and is typically twice 

 forked, as is also the median vein, while the subcostal and 

 cubital veins are but once forked. 



