276 The Ohio Journal of Science [Vol. XX, No. 7, 



24. Large species, 6 mm. in length; fifth abdominal stemite glossy along 



inner margins of the processes; inferior hypopygial forceps short and 

 stout, curved, and with a tooth at middle on inner side. . . .denticauda sp. n. 

 Smaller species, 4 mm. in length; fifth abdominal stemite and hypopygium 

 not as above 24a 



24a. Hind femur with a few long fine bristles on basal half of posteroventral 

 surface; fifth abdominal stemite with very short fine hairs along inner 



margins of processes, but not fringed subnitida sp. n. 



Hind femur with short fine bristles on entire length of posteroventral 

 surface; fifth abdominal stemite as in Figure 11, the inner margin of 

 each process densely setulose at middle parvicornis sp. n, 



25. Prealar bristle over half as long as the bristle behind it; hypopygium as 



Figures 28 and 44 tridens sp. n. 



Prealar bristle much less than half as long as the bristle behind it; 

 hypopygium as in Figures 29 and 41 substriata Stein 



Hylemyia triseriata sp. n. 



Male. Black, faintly shining, densely pale gray pruinescent. 

 Anterior margin of interfrontalia and lower part of parafacials slightly 

 rufous brown. Thorax with three narrow dorsal brown vittae. Abdo- 

 men with a black dorsocentral vitta which is slightly dilated at anterior 

 margin of each tergite. Legs black. Wings slightly grayish, veins 

 brown, paler basally. Calyptrse white. Halteres yellow. 



Narrowest part of frons as wide as distance between posterior ocelli ; 

 interfrontalia distinct on its entire length, with a pair of fine bristles 

 above middle; parafacial at base of antenna about 1.5 as wide as third 

 antennal segment, very little narrowed below; cheek a little higher than 

 widest part of parafacial, with numerous bristles along and slightly 

 above lower margin, one strong one directed downward at middle and 

 several weaker upwardly directed shorter bristles between it and anterior 

 angle; arista pubescent, much swollen at base; third antennal seginent 

 about 1.5 as long as second. Presutural acrostichals very close together, 

 two strong and two or three weak pairs ; prealar about one-third as long 

 as the bristle behind it. Abdomen moderately depressed, parallel-sided; 

 fifth sternite with moderately stout processes, which are bare along their 

 inner marghis except at apex, where there are abottt four short, blunt 

 setulse, the outer half with ntmierous long bristles. Legs as in fusciceps 

 Zetterstedt, the mid tibia with a strong anterodorsal median bristle, 

 and the hind tibia with an anteroventral series of rather strong setulose 

 hairs and the posterior and posteroventral surfaces each with a series of 

 longer weaker setulose hairs. Costal thorn of moderate length. 



Length, G mm. 



Type, Katmai, Alaska, June, 1917. One male. 



This species must be very closely related to Hylemyia 

 (Phorbia) biciliata Coquillett, but the distinct markings on 

 thorax and abdomen and different structure of the head appear 

 to warrant its separation therefrom. 



