120 PROC. ENT. SOC. WASH., VOL. 23, NO. 5, MAY, 1921 



at Carlisle, Pennsylvania, by C. C. Hill, April 20, 1919, from the 

 same host; and one male paratype reared by P. R. Myers, April 

 30, 1919, with the same locality and host. Antennae of type and 

 allotype mounted on a slide. 



Mr. McConnell states that the species is a primary parasite 

 and that only a single individual is obtained from a host larva. 



DISTRICT OF COLUMBIA DIPTERA: SCATOPSIDAE. 



BY W. L. McArEE. 



These small to minute black flies have long been placed in the 

 Bibionidae, but seem better grouped as a separate family. They 

 breed in decaying vegetable matter and in excrement; in the 

 adult stage they are most easily found in flowers and on windows. 

 The most useful American paper on the family is that of Dr. A. 

 L. Melander (Bui. 130, Washington Agr. Exp! St., April, 1916). 

 It is based on a European revision of the genera by G. Enderlein 

 (Zool. Anz. Vol. 40, pp. 261-282, October, 1912). In the last 

 named paper genera are founded on trifling differences in vena- 

 tion which may not prove wholly satisfying; in fact one of them 

 is synonymized on a subsequent page. Other genera of Ender- 

 lein's are used but it must be admitted that in certain cases only 

 a little variation would link them up. The only genus here 

 treated that has a distinct habitus is Aspistes. 



Key to the genera. 



A. Front tibia ending in a decurved sharp pointed process; thorax strongly 

 elevated anteriorly, the declivity coarsely punctured; wing without 

 apical cell, i. e., anterior branch of fourth vein interrupted basally. 



Aspistes. 



AA. Without the preceding combination of characters. 



B. Anterior branch of fourth vein strongly angulate near base or emitting 

 a crossvein which extends part way or entirely to third vein 



Scatopse. 



BB. Anterior branch of fourth vein neither angulate nor emitting a cross- 

 vein. 

 C. Apical wing cell present. 



D. Apical cell much shorter than its stalk Swammerdamella. 



DD. Apical cell longer than its stalk. 



E. Last vein of wing with a single curve; vein 3 remote from 

 costa, section from radial crossvein to costal margin 

 strongly curved into wing; radial crossvein near middle 

 of second vein; subcostal cell usually larger than costal; 

 halteres white; hind tibiae abruptly expanded distally 



.. Reichertella. 



