THE DIPTEROUS GENUS DOLICHOPUS IN NORTH AMERICA. 137 



anal angle nearly obsolete, the wing being narrowed toward its 

 base. 



Female. — Face broad; costa without enlargement at tip of first 

 vein; anal angle of wing a little more developed; middle tibiae with 

 one bristle below, their basitarsi without a bristle above. Cilia of the 

 calypteres yellow ; there are specimens which seem to belong to this 

 variety that have these cilia black, but they may be the females of 

 some other species. The fifth joint of fore tarsi black, not paler than 

 those preceding it. 



Described from numerous specimens from the following localities: 

 New Hampshire; western New York, June 29 to August 4; Ontario, 

 May 16-July 28; Quebec, July; Summerside, Prince Edward Island, 

 Canada, July 21 (E. M. Walker). 



2^/2^6.— Male, Cat. No. 23019, U.S.N.M., from Toronto. 



This variety is of uncertain value. Some may not think it should 

 have a distinctive name, others might even consider it a distinct 

 species. 



The two species socius and hrevimanus have long been confused. 

 Prof. J. M. Aldrich considered them synonymous after examining the 

 types, but although I could find no difference of value when I looked 

 over the type material in January, 1919, still it is my opinion that they 

 are distinct species and that the specimens standing under hrevimanus 

 in the Loew collection are not the ones he described the species from; 

 they do not quite answer his description, which gives the difference 

 between the two forms very clearly. I find both forms in the material 

 now in my hands. The most noticeable difference between them is 

 that in hrevimanus the black hairs on the sides of the hind femora 

 descend to its lower edge, so that when viewed from below they show 

 two rows of little black hairs with a glabrous space between them; 

 while in socius there is a row of delicate little yellow hairs on the lower 

 inner edge, which although sometimes easily overlooked can always 

 be seen. 



In going over the material having these yeUow hairs on lower inner 

 edge we find two forms which have quite a different appearance, 

 still when we come to look for distinguishing characters they are not 

 so easily separated as one would think. One series has the fifth joint 

 of the fore tarsi yellow (in fact, the fifth joint of all the tarsi is more 

 or less yellowish, at least at tip), the other series have the fifth joint 

 of fore tarsi black, not paler than those preceding it. I found that 

 the type specimens had the fifth joint yellow, so the first series is the 

 typical form of socius Loew. 



In the series before me, those with the yellow fifth joint also have 

 the face a trifle more yellow on upper part; third antennal joint dis- 

 tinctly larger and longer, the first joint also seems to be more broadly 



