588 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



yet not so prominent that systematists have ascribed an appendiculate 

 cell to this genus. In the genera Perreyia (fig. 9, e), Dielocerm (fig. 

 10, a), Pterygophorus (fig. 10 c), LaUdarge (fig. 10, d), Sirex (figs. ST- 

 BS), and Treniex (fig. 10, <?), all of whicli are considered as having an 

 appendiculate cell, there is a perfect series from the condition found 

 in Tenfhredo and ClaveUaria to those genera in which the appendic- 

 ulate cell is well marked. This series also shows clearly that the vein 

 projecting from the apex of the cell 2d R^+R, in Tremex is not of 

 secondary origin but is vein Rj, which has moved in from the margin 

 of the wing and that vein Rj ends at the point where it joins R^. The 

 formation of the appendiculate cell has arisen through the necessity 

 for a stift'ening of the apex of the wing. 



THE MEDIAL AREA. 



The point of separation of the stem of media from radius and the 

 position of the medio-cubital cross-vein are so intimately associated 

 that they will be discussed together. Media is found in its most primi- 

 tive condition in the wings of Mmwxyela (fig. 3-1), where it separates 

 from radius very nearly midway between the stigma and the base of 

 the wing. It does not bend down at right angles, as is the case in 

 most of the veins of the Hymenoptera, but branches off in a manner 

 similar to that found in the branches of radius and media in the dip- 

 terous wing. This has a marked effect on the size and shape of the 

 cell R, which is here three times as long as it is broad at its widest 

 point. The medio-cubital cross-vein also occupies a very generalized 

 position. It is located at the apex of the cell R, almost interstitial 

 with the radio-medial cross-vein, while in all other Tenthredinoidea it 

 is found at or near the base of the cell R. In Macroxyela (fig. 33) we 

 find a slight modification of the condition found in Manoxyela. Here 

 media has combined with radius for a greater distance, separating 

 from radius distinctly beyond the middle of the distance between the 

 stigma and the base of the wing, while the cell R is only about twice 

 as long as broad. The medio-cubital cross-vein arises from near the 

 apex of the cell R and is about the same length as the portion of 

 media between it and radius, the two standing at about the same 

 angle like the top of a Y. In all other Tenthredinoidea the media 

 has coalesced with radius for a much greater distance — for at least 

 three-fourths of that portion of radius extending between the stigma 

 and the base of the wing. In Xiphydrla (fig. 85) media arises very 

 much as in the wings just described and the medio-cubital cross-vein 

 is transverse and placed just before the middle of the cell R. The 

 wing of OryssKS (fig. 97) is another interesting example. In this wing 

 the reduction in the number of wing veins has been carried farther 

 than in any other Tenthredinoidea, yet as regards the origin of media 

 and the position of the medio-cubital cross-vein it is practically the 



