70 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



Phrosinella is holarctic in distribution. The species in North 

 America, so far as known, are distinct from those of Europe, and have 

 not been taken outside of the United States. There are four Nearctic 

 species, each with a somewhat restricted range. 



The flies of this genus, as far as known, occupy the ground-subter- 

 ranean stratum, being found in the adult stage largely on barren 

 ground, in and about the holes of burrowing Hymenoptera, rarely on 

 low foliage. They are not commonly attracted to flowers, but at 

 least one species frequently feeds on honeydew. It is believed that 

 they are biologically superimposed upon fossorial Hymenoptera, but 

 reliable rearing records are lacking. Dissections of one species indi- 

 cate that they deposit large, active maggots. The female of this 

 species has also been observed digging a pit in the sand near the bur- 

 rows of fossorial Hymenoptera, for which its flattened fore tarsi are 

 admirably adapted. Larvae were deposited in the pit. It seems 

 probable that from this point, they burrow^ through the soil to the 

 cell of their host, a form of activity which may be correlated with the 

 presence of a conspicuous spiniferous foot on the ventral part of the 

 last segment of the first instar maggots. Pupation takes place in 

 the soil, apparently not far from the cell of the host, 



KEY TO NORTH AMERICAN SPECIES OF PHROSINELLA 



1. Third antennal joint black 2. 



Third antennal joint bright yellow, rarely overlaid with blackish tomentmii. 



fulvicornis (Coquillett). 



2. Third abdominal segment with black polished apex which is devoid of pollen, 3. 

 Third abdominal segment pollinose to apex, at most with small black spots 



about the marginal bristles; wings distinctly infuscated; thorax and abdo- 

 men grayish pollinose with brownish tinge fumosa, new species. 



3. Front distinctly hairy, many bristly hairs on frontal vitta between frontal 



rows; males with conspicuous tuft of hairs on underside of second tarsal 

 joint of fore leg, tliird tarsal joint much thicker and shorter than the fourth. 



pilosifrons, new species. 



Front almost destitute of hairs, vitta bare; males with conspicuous tuft of 



hairs on outside of second tarsal joint, third joint scarcely wider than the 



fourth aldrichi, new species. 



PHROSINELLA FULVICORmS (Coquillett) 



Gyi?inoj)rosopa fulvicornis Coquillett, Journ. New York Ent. Soc, vol. 3, 



p. 106, 1895. 

 Hilar ella fulvicornis Coquillett, U. S. Bur. Ent., Tech. Ser., No. 7, pp. 17, 128, 



1897. — Smith, Ins. of New Jersey, p. 782, 1909. — Cole and Lovett, 



Proc. Cal. Acad. Sci., vol. 11, p. 303, 1921.— Buimley, Ent. News, vol. 33, 



p. 23, 1922. 

 Euhilarella fulvicornis Townsend, Proc. Biol. Soc. Wash., vol. 28, p. 22, 1915. 

 Phrosinella fulvicornis Allen, Occas. Pap. Bost. Soc. Nat. Hist., vol. 5, 



p. 92, 1924. 



Male. — Front at narrowest 0.35 of head width (measurements of 

 five, 0.30, 0.35, 0.35, 0.37, 0.39) ; front, including the vitta which is 

 scarcely distinguishable, white or sometimes golden pollinose; vitta 



