143S. WINGS OF THE TFXTHREDIXOTDEA—Ma cdlLIJVR. IT. 617 



the way in which the progressive moditicationsof each part has arL^en. 

 Let us now consider the interrehition of the various parts in its bear- 

 ing- on the phylogeny of the group as a whole, and its bearing on the 

 relation of the Tenthredinoidea to the other superfaniilies of the 

 Hynienoptera. 



The superfaniily Tenthredinoidea is a homogenous group easily 

 demarcated from all other Ilymenoptera l)y sexeral structural charac- 

 tei"s other than those found in the wings. The effect of natural selec- 

 tion on their wings has tended to modify them along so many different 

 lines that it would be strange if we should find any single character 

 that would circumscribe the group. This has been found to be true, 

 though the separation of 

 the group is readily accom- 

 plished by the employment 

 of several coordinate char- 

 acters. 



As has already l)een 

 ])ointed out several times, 

 the superfamilj' Tenthredi- 

 noidea contains all those 

 genera of the Il3mienoptei'a 

 that are especiall}" general- 

 ized, as the free part of the 

 veins R,, Cu.^, 2d A, and 8d 

 A is found only within the 

 limits of this superfamily. 

 The great majority of the 

 members of this superfam- 

 ily can be distinguished by 

 the presence in the front 

 wings of either the second 

 or third anal cells or both. 

 In a few subfamilies of the 



family Tenthredinidie both of these cells are w^anting. But these sub- 

 families, Incaliina?, Acordulecerinae (fig. 83), Lobocerina? (fig. 82), 

 Pter3^ogphorina^ (fig. 81). and Pergina^ (fig. 84), of which only the 

 second is represented in our fauna, are easily distinguished by the 

 position of the medio-cul)ital cross-vein, which always extends 

 between radius and cubitus, while in all other Hymenoptera other 

 than the Tenthredinoidea, and even in certain members of the Ten- 

 thredinoidea, as has already been shown, this cross-vein always 

 extends betAveen media and cul)itus. Other minor difl'erences that 

 should be noted are the preservation of a nuich greater number of 

 veins in the radial and medial areas of the hind wings — this is true 

 even in those subfamilies in which the anal cells of the front wings 

 have been suppressed — and the preservation of the third anal vein 



Ffg. 19. — The base of the radial sector, a, C.enolyda 

 semidea; b, Tenthredo flava: c, Cladius pectini- 

 coRNis; d, Paururus CYANEUS; e, Megalodontes spissi 



CORNIS. 



