NO. 1438. WIXGS OF THE TENTHREDINOIDEA—MacGILLIVRAY. 641 



of the wing along Sc+R+M. This is conclusive!}^ shown in Trichio- 

 soma (fig. 59), where the cross-vein has migrated more than its own 

 length away from the origin of media. That this latter solution is 

 untenable is further proven by the position of the posterior end of the 

 radio-medial cross-vein, which in both the Siricidas and Megalodontida? 

 is so near the posterior end of the transverse part of media as to pre- 

 clude such a migration. 



It has been shown that the preservation of the radial cross-vein as 

 the base of Rj, as in the Or3'ssidte, is the same condition existing in all 

 the higher Hymenoptera. It is of especial interest that the form of 

 the medio-cubital cross-vein and the base of media is also the same 

 arrangement of parts found in the other Hymenoptera. Both of 

 these conditions go to show that the other superfamilies of the Hyme- 

 noptera were derived from a progenitor closely allied to the families 

 Siricidre, Megalodontida?, and Oryssida?. 



Xip/tydrlidR'. — This famil}' contains four genera and about twenty- 

 five species, which are distributed over North and South America, 

 Europe, and Asia. Their wing type (fig. 85) is the most generalized 

 found in the specialized Tenth redinoidea. The front wings are long 

 and narrow; the costal area is broad and distinct; the free part of SCj 

 is represented by a prominent transverse vein situated near the origin 

 of media, which is a direct modification and migration of the condition 

 found in Xyela (fig. 35) and Manoxyela (fig. 34); the anterior end 

 of the radial cross-vein is situated near the apex of the stigma and its 

 posterior end near the apex of the cell R:^ or interstitial with the free part 

 of the vein R5 and is either perpendicular or slightly oblique; this cross 

 vein is wanting in the genus Derecyrta. The radial sector arises at 

 the base of the stigma and continues along R3 in a regular curve. The 

 base of the sector is subtrans verse; it does not make as abrupt a bend 

 as in the generalized Tenthredinoidea, while, on the other hand, it is 

 not so gradual a curve as in the more specialized forms. The radio- 

 medial cross-vein is somewhat oblique and distant from the origin of 

 media, and is wanting in the genus Koncmua. Media separates from 

 radius but little nearer the stigma than in the Lydida?, while the 

 portion before the medio-cubital cross-vein is oblique, just as in Macro- 

 ,ri/ela (fig. 33), though ])oth this part of media and the cross-vein are 

 longer than in that genus, resulting in a much wider cell M; the free 

 part of M^+Cuj is near the posterior end of the radio-medial cross- 

 vein, almost interstitial with it. In the hind wings the origin of media 

 is distant from the origin of the radial sector, and the first anal cell 

 is of a type similar to that found in the Lydidae (figs. 36-43) except in 

 Konowia^ where it is open at the apex. 



The migration of the apex of Ri in the front wings away from the 

 margin of the wing in XiphydHa camelus, as already described, 

 has developed into a distinct appendiculate cell in Derecyrta and 

 Brachyxiphus. 



