K0.1438. WINGS OF THE TENTHREDINOIDEA—MacGILLIVRAY. 599 



dinoidea except in the family Cephid* (tigs. 93-96), where it has 

 been completely squeezed out by the close apposition of eosta and 



Sc + R + M. 



THE RADIAL AREA. 



The bases of radius and media are combined in the same way as in 

 the forewing. The single vein R-[-M extends to near the middle of 

 the wing, where it divides into R^ and R^+M. In most specialized 

 Tenthredinoidea the stem of R+M is only moderately thickened, but 

 in Oryxsns (tig. 97), the costa being wanting, the vein R+M has been 

 excessively thickened, evidently to take up the stress that would have 

 been transmitted along the costa. 



Rj combined with Scg extends obliquely to the front margin of the 

 wing, where it anastomosis with costa in a single point, or at most for 

 only a very short distance, just before the apical area of hooks, then 

 curves awa}^ from the costa and joins it again at the apex of the apical 

 area of hooks, forming a cell Sc^ homologous with the stigma of the 

 front wings. This cell is prominent in such genera as Peridlsta (tig. 

 69), Pteronus (tig. <6^)^ Phyntatocera (tig. 71), Strongijlogaster (fig. 51), 

 Dineura (fig. 63), Dolerm (fig. 49), Tenthredo (fig. 56), and Trichlo- 

 soma (fig. 59), and is generally situated at the liase of the cell R^+g. 

 In the Xyelidffi (figs. 31-35), Xiphydriid^e, Cephida^ (figs. 93-96), 

 Megalodontida, and Blasticotomid* (fig. 44), this stigma-like cell is 

 entirely wanting, while the apical area of hooks is situated on an 

 enlargement of the costa opposite the middle of the cell Rj+o. This 

 cell is faintly indicated in the Lydida^ (figs. 36-43) and situated as in the 

 Xyelidfe, while in the Tenthredinidaj it is generally distinct except in 

 the more specialized subfamilies. This is especially true in those 

 genera with an appendiculate cell. The course of the apex of R^ here 

 confirms our conclusions regarding its course around the stigma in the 

 front wings and that the stigma is nothing more than a stronger 

 chitinization of the wing membrane in front of R^ than is found in the 

 other cells. 



The front margin of the cell R1+2 in the Siricidse (figs. 86-91), Mega- 

 lodontidfe (fig. 92), Xyelid;e, Lydidte, and Blasticotomida^ is l)ounded by 

 a vein of uniform width, Rj, which, after joining the costa beyond the 

 apex of the apical area of hooks, coalesce with it, the single vein extend- 

 ing along just within the front margin of the wing. It ends in the 

 Xyelida (figs. 31-35), Lydida (figs. 36-43), Megalodontid* and Blasti- 

 cotomida3 (fig. 44), at or slightly beyond the apex of R3 and a con- 

 siderable distance liefore the apex of the wing. This results in a cell 

 contour identical with that found in the front wings. In most genera 

 of the family Tenthredinidje, as Macrophya (fig. 56), Blennocampa 

 (fig. 72), Stromhocrros (fig. 50), Peridkta (fig. 69), and Pteronus (fig. 

 68), Rj likewise ends at or slightly beyond the apex of R.^, but in these 

 genera the veins R^ and R3, coincident with the lengthening and nar- 



