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.