AMERICAN DIFTERA. 81 



THE DIPTEROU$$ OEIVERA TA4 HYTREC HUS 

 AND MAC'EEEOCJERUS. 



BY J. M. ALDRICH. 



This group of the Dolichopodidse contained, at the time of Loew's 

 monograph, one genus and three species. Since then Loew published 

 another species in his seventh Century, and Osten Sacken one in 

 " Western Diptera." Mik has established a new genus for a part 

 of the old one, and three new species are described in the present 

 paper. 



These two genera form a well-defined group, with the following 

 characters : First antennal joint hairy above, arista dorsal, face 

 long, narrow, wider below and rounded at the tip, reaching as low 

 as the inferior border of the eye ; wings narrow, in the male espe- 

 pecially ; hypopygium of the male entirely disengaged, directed for- 

 ward under the venter, reaching nearly to the coxae ; hind metatarsi 

 without bristles above. 



The genera are separated by the following characters : 



Male antenupe normal, like those of the female; fourth longitudinal vein ending 

 just before the extreme apes, at a considerable distance from the tip of the 

 third Tachy trechus. 



Male antennje with the second joint rudimentary and the arista elongated and 

 ending in a lamella; fourth vein ending considerably before the apex, veiy 

 close to the tip of the third IVIacellooerus. 



Tachytrechus Loew. 



Stauuiiis isis 1831, p. 261, Loew, Neue Beitraege. v, 1857; Mou. Dolicho- 

 podidae, p. 109. 



31 ALES. 



1. Wing of male with a spot at the tip 2. 



Wing of male without spot aiignstipennis Loew. 



2. The spot wholly black florideiisis n. sp. 



The spot black in front, snow-white behind vorax Loew. 



FEMALES. 



Posterior femora yellow at the extreme tip only Torax. 



Posterior femora about a third of the length yellow florideiisis. 



(The female of angustipeiinis is not known.) 



TBANS. AM. E.VT. SOC. XXIII. (11) MARCH, 1896. 



