APHIDID^ 517 



whereas, as is usual in the higher groups of Aphidiuiu, the sixth joint 

 is shorter than either of these joints, and, since our Alaska insect 

 agrees in coloration and other important characters, excepting the 

 nectaries, with Kaltenbach's description, I take it for granted that it 

 belongs to the same species. 



It may be of interest in this connection to point out that Ptero- 

 co/fima pilosa Buckton, belongs also to this genus and that his 

 Pterocomma has to be dropped. In examining the type specimen 

 of Pterocojuma pilosa^ which had been kindly loaned me by Dr. 

 Buckton for study, I was surprised to find that the principal char- 

 acter, the peculiar shape of the wings, on which this genus was 

 founded, does not exist, but that it was the result of poor preparation, 

 by which a peculiar fold along the third discoidal vein was formed, 

 which can be readily traced by gently focusing this part of the wing. 



It is quite possible that his species may belong to the same species ; 

 at least, it appears to come very near to it. 



Additional studies of other genera with more or less distinctly clavate 

 nectaries have convinced me that the genus Melanoxanthus Buck- 

 ton has also to be dropped and that it must be made a synonym of 

 Cladobius. The clavate character of the nectaries in different species 

 varies considerably, so that it frequently may happen that the clavate 

 character of rather slender nectaries is overlooked, especially if they 

 lay parallel with, or close to the abdomen. The general appearance, 

 however, of these insects, their rather large size, strong pilosity of the 

 body and its members and the minute, blunt tail, will not fail, even if 

 the exact shape of the nectaries cannot be ascertained, to assign them 

 to their proper position. 



The synonymy of this genus will therefore read : 



CLADOBIUS Koch. 

 Melanoxanthus Buckton. 

 Pterocofnma Buckton. 



