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



Hylemyia tridens sp. n. 



Male. Similar in color and general habitus to sericea. Differs 

 from sericea in structure of hypopygium (Figs. 44 and 28). The 

 prealar is as in appendiculata. 



Length, 6 mm. 



Type and one paratype, Savonoski, Naknek Lake, July and 

 August, 1919. 



FAMILY SCATOPHAGID.E. 



Amaurosoma Becker. 



I included this genus in my key to the genera of Scatophag- 

 idse in a paper on the Diptera collected by the Canadian Arctic 

 Expedition, but up to the present no species of this genus has 

 been recorded from America. In the present paper I describe 

 three species as new. 



The adults are predaceous, feeding on small Diptera and 

 other small insects; the immature stages are unknown. 



Amaurosoma katmaiensis sp. n. 



Female. Black. Head with whitish pruinescence; thorax opaque, 

 gray pruinose; abdomen shining, with very slight pruinescence. Head 

 black; interfrontalia whitish yellow, face and cheeks concolorous; 

 antennae black, second joint inconspicuously yellow at apex; arista 

 black; proboscis black; palpi yellow. Thorax not vittate. Legs black, 

 tibiae and tarsi flavous, the tarsi of mid and hind legs slightly darker. 

 Wings clear, veins black. Calyptra white. Halteres yellow. 



Frons fully half the width of head ; orbits narrow anteriorly, becoming 

 wider to anterior ocellus, the bristles rather weak; face slightly receding 

 below; antennae stout, nearly as long as face, third joint with sharp 

 upper apical angle, rounded below; arista almost bare, inuch swollen 

 on basal third; vibrissa strong, a strong bristle below it. Thorax with 

 the presutural acrostichals weak, two-rowed. All abdominal segments 

 with widely spaced bristles on posterior margins. Legs normal; fore 

 femur with about nine long fonvardly directed bristles in two to three 

 irregular series on middle of antero-ventral surface; mid femur with six 

 or more widely spaced bristles in similar situation; antero-ventral 

 surface of hind femur with three or four widely spaced bristles; fore 

 tibia with three bristles, one anterodorsal, one posterodorsal and one 

 posterior; mid tibia with one bristle on each of the following surfaces — 

 antero ventral, anterodorsal, posterodorsal and posterior; hind tibia 

 with two or three anterodorsal and two or three posterodorsal bristles. 

 Last section of fourth vein two or three times as long as preceding section; 

 outer cross-vein at or more than its own length from apex to fifth vein. 



Length, 4.5-6 mm. 



