May, 1920] Descriptions of Diptera 271 



longest hairs on arista about equal in length to width of third antennal 

 segment; cheek about equal in height to widest part of parafacial. Two 

 or three pairs of strong acrostichals and many interspersed hairs in front' 

 of suture; prealar very short; hypopleura bare. Abdomen narrow, 

 subcylindrical, tapered apically; no ventral tufts present; hypopygium 

 small, the inferior forceps very long, sUghtly sinuous, thickened on 

 apical half; fifth sternite with processes elongate, subcylindrical, their 

 inner margins with a few fine hairs, their outer margins with a number 

 of long bristles. Fore tibia with a median posterior bristle, the apical 

 posterior bristle long; mid femur with some long bristles on basal half 

 of postero ventral surface; mid tibia with an anterodorsal, and two 

 posterodorsal and posterior bristles; hind femur with a series of antero- 

 ventral bristles and three or four bristles on middle of posteroventral 

 surface; hind tibia with three or four posterodorsal, about eight antero- 

 dorsal and two or three antero ventral bristles, and two or three posterior 

 setulae. Costal thorn very short; outer cross-vein curved, very 

 oblique. 



Length, 7.5 mm. 



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



Hydrophoria congrua sp. n. 



Male. Black, shining, with bluish gray pruinescence, most distinct 

 on abdomen. Orbits and cheeks silvery when viewed from the side 

 above. Thorax rather indistinctly quadrivittate. Abdomen with a 

 black dorsocentral vitta, which tapers slightly posteriorly. Legs 

 black. Wings slightly grayish. Calyptree white. Halteres dull yellow. 



Narrowest part of frons about as wide as distance across posterior 

 ocelli; orbits haired to above middle; interfrontalia with a pair of fine 

 bristly hairs above middle; parafacial a little wider than third antennal 

 segment, hardly narrowed below; cheek as high as widest part of para- 

 facial; arista with very short pubescence; third antennal segment not 

 much longer than second. Thorax without distinct presutural acro- 

 stichals ; prealar about half as long as the bristle behind it ; hypopleura 

 bare. Fifth tergite shining, pruinescent, with a few fine hairs; basal 

 hypopygial segment with some long bristly hairs which are curved 

 upward; fourth tergite not conspicuously bristly on sides; fourth 

 sternite without conspicuous bristles; fifth steniite with rather short 

 processes which are fringed with fine hairs on apical half of inner margins 

 and have a dense fringe of longer setulose hairs at bases. Fore tibia 

 with an anterodorsal and posterior bristle near middle; mid femur with 

 long bristles on posteroventral surface; mid tibia with one antero ventral, 

 one posterodorsal, three posterior and one posteroventral bristles; 

 hind femur with long bristles on anteroventral and posteroventral 

 surfaces, those on the last surface interrupted beyond middle; hind 

 tibia with three anteroventral, seven or eight alternately long and short 

 anterodorsal, and three long and one or two short posterodorsal bristles, 

 posterior surface bare. Costal thorn short. 



Length, 6.5 mm. 



Type and paratype. Anchorage, Alaska, June 6, 1917. 



