NO. ] 438. WIAGS OF THE TENTHREDINOIDKA—Ma cGILLJ I 'RA Y. 621 



these otfsprino- have all arrived at ditfcrent sta<>"es in their ascent, and 

 by a comparative .study it is possible to determine^ the road along- 

 which they have traveled. From this it is evident that in this super- 

 family those characters of value as essential characters are ecpially 

 valuable as recognition characters. 



The relation of the families of the Tenth redinoidea can be best 

 shown by the foUowing synopsis. 



SYNOPSIS OF THK FAMILIES OF TENTHKEDLXOIDEA. 



The generalized Tentliredinoidea Xyelida'. 



Lydidi*. 

 The specialized Teiithredinoidea: 



The cell R^ groni) Blasticotomida^. 



Tenthredinidte. 



The cell R5 group Xiphydriidye. 



Siricida'. 

 Megalo<lontida\ 

 Cephida. 

 Oryssidte. 



THE GENERALIZED TENTHRP:DIN0I1)EA. 



The generalized Tentliredinoidea embraces two families, both of 

 which are near the stem form of the original j)rog(Miitor of the Hyme- 

 nopteria. They are marked as generalized types ])v their short, broad, 

 many-veined wings, in which the veins have not l)een arranged to the 

 best advantage for stitiening the stigmatal and anal areas. They are 

 further distinguished by the origin of the radial sector distinctly 

 before the stigma, and by its prominent subtransverse bend away from 

 the stigma. The course of the apex of the vein R, in both wings also 

 demarcates them; this vein near the point of origin of the \ein R; bends 

 abruptly toward the margin of the wing, so that the cell on its front 

 side, R, or 2d R^+R., is blunt or subtruncated at apex, a condition 

 found only in generalized genera. 



This group is of particular interest to the student of phjdogenies, 

 because it approaches nearest to the t\"pical wing in its retention of 

 subcosta, the free part of 11.^ and the free part of Cu.,, though this 

 latter is also found complete in one genus of Sii-icida'. 



Xyelldx. — A small family embracing live genera and a limited niun- 

 ])er of species, which are confined mainly to the American fauna. It 

 is easily separated from all other Hymenoptera by the presence in its 

 wings of the free part of the vein R.^. The family contains, at least 

 so far as their wing venation is concerned, the most generalized Hyme- 

 noptera known (figs. 31-35). This is shown by the origin of media 

 near the middle of the costal area; })V the perfect transverse direction 

 of the radial cross- vein, which is situated midway l)etvveen the radio- 



