626 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxi.x. 



THE CELL R, GROUP. 



It has l)een noted that there are two iiioditications in the stignuital 

 region that go hand in hand. The one is the progressive coalescence 

 of the media from the middle <^f the costal area to near the stigma; the 

 other is the progressive migration of the medio-cubital cross-vein from 

 a position near the apex of the cell R to a position in the angle between 

 R and M. In the cell R^ group there is found the consummation of 

 these modifications, the base of the media moving still nearer the 

 stigma and the cross-vein cutting loose from media and migrating 

 along Sc+R+M until in some genera it is more than its own length 

 away from the media. It is doubtful that this moving of the radial end 

 of the cross-A'ein toward the base of the wing is in ever^^ case a bona 

 tide migration, and herein probably lies the explanation of why this 

 chai-acter is of little value in certain subfamilies of the Tenthredinida?, 

 If the wings of Strongylog aster (tig. 51), SfroiiiJxK'eros (tig. 50), and 

 Selandrla, are examined, it is found that in the tirst the cross-vein 

 arises in the angle between R and M, and that radius extends toward 

 the stigma in a regular curve; in the second the cross- vein is farthest 

 from M, but that beyond the cross-vein radius makes a more promi- 

 nent bend toward the stigma, while in the third the cross-vein is dis- 

 tant from M and radius makes an abrupt bend toward the stigma. 

 The evidence here suggests that in the case of Selandria this condi- 

 tion was reached ])y a coalescence of the anterior end of the cross-vein 

 and Sc+R+M. 



This group is noteworthy as being the only one showing the diti'erent 

 ways in which the anal area has been moditied and therefore the suc- 

 cessive changes that have resulted in the complete reduction of the 

 anal cells. 



The position of the radial and medio-cubital cross-veins marks the 

 group as a sidewise development, this arrangement of parts being 

 peculiar to the group. With the exception of a single case in the cell 

 Rj group, it is the only place where the radial cross-vein is lost. 

 This peculiarity has arisen independently a number of times in the 

 family Tenthredinid*. When present, this cross-vein is always oblique 

 to R3+4 and never perpendicular, as in the generalized Tenthredinoidea. 



The hind wings are practically the same in venation as those of the 

 Lydidje, except that in some forms the free part of the second anal, 

 the free part of R^, and the transverse part of M. has atrophied. 



Blmtlcotoinidx.—Ps. family containing a single genus and species, 

 found only in central and eastern Europe (tig. 44). This is an isolated 

 archaic type. It is, in certain of its characters, closely related to the 

 Xyelida' and Lydidic; in others it approximates the Tenthredinidea; 

 that is, it is intermediate between these two groups. The area between 

 costa and Sc+R+M is hardly more than a line and all trace of the sub- 



