NO. 143cS. 



WIXGS OF THE TENTHREDINOIDEA—MacGILLIVRAY. 581 



two distinct parts, a long basal portion Sc and a small area at the 

 apex of the small free part of the vein Se. and in front of the vein 

 R,. This cell in all Hymenoptera is strongly chitinized and is known 

 as the stigma. 



The costa, C, is situated on the front margin of the wing and does 

 not undergo any marked moditications. 



M^R. 



1st A+2d A+3d A+Cu^^^+3I^ ]t/ 



Fig. t'l. — Modified hypothetic ai, type. 



Thus far there has been considered only a hj^pothesis as to how tlie 

 most generalized hymenopterous wing known could have been formed. 

 The data upon which this hypothesis is founded is not original with the 

 writer but is based on facts first pointed out by Prof. J. H. Comstock 

 in his Manual for the Study of Insects and Elements of Insects Anatomy. 

 Let us now look at a few of these facts on which this hypothesis is 

 based. If a careful stud}- be made of a number of wings of the 

 Diptera, one of the most striking facts noted will be that ""there is a 



4+5 



1st A+2d A+3d A-i-Ou^+2+31, 



-Modified hypothetical type. 



marked tendency for veins to coalesce from the margin of the wing 

 toward the base." In fact, if the wing of Jlidas (fig. 28) be examined, 

 it will be seen that a larger proportion of the veins are coalesced at 

 apex than in any known hymenopterous wing. If Cu.^ and 1st A be 

 examined in the wings of Pa/darhes (fig. 21), Mri.v (fig. 22), Tahairm 

 (tig. 23), Scenophius{1ag. 24), Rhamphoinylai^g. 25), and Jl/i^§c« (fig. 26), 



