PROC. ENT. SOC. WASH., VOL. 22, NO. 2, FEB., 1920 29 



D. Hind femora wholly black. 



E. Tibiae almost wholly black, sometimes with traces of 

 reddish at base; decidedly small species with much sil- 

 very hair underneath head and thorax maneei. 



EE. Tibiae in part, or chiefly, pale. 



F. Front and middle femora yellow with black stripe on 

 upper side; mystax black and golden in male; last 

 3-4 segments of abdomen of female modified as 



ovipositor flavofemoratus. 



FF. Front and middle femora black. 



G. All tibiae pale only at base; all metatarsi black; 

 mystax black and white. 



H. Male forceps more slender and straight 



vir ginicus. 



HH. Male forceps stouter and decurved at tip 



notatus. 



GG. Tibiae with more extensive pale markings. 



I. Male forceps heavy, longer than last two ab- 

 dominal segments together; mystax largely black 



sadyates. 



II. Male forceps more slender and shorter; mystax 



largely pale. 



K. Mystax mostly white; male forceps not much 



narrowed or decurved at tip. .novaescotiae. 



KK. Mystax with more dark hairs, general color 



a little more fulvous ; male forceps decurved 



at tip autumnalis. 



DD. Hind femora with pale markings. 



L. Male forceps seen from above, wider at or near apex than at base; 



eighth abdominal segment of female (that is, basal segment of 



ovipositor) longer than 6th and 7th together; arista equal to or longer than 



third antennal joint. 



M. Male forceps wider than abdomen at middle; dark species, legs 

 black with reddish or yellowish markings. 



N. Wings narrow, male genitalia more than 2 mm. wide 



angustipennis . 



NN. Wings wide; male genitalia less than 2 mm. wide, latipennis. 



MM. Male forceps, not wider than abdomen at middle; yellowish 



gray species; mystax largely golden yellow; legs yellowish 



with dark markings auricomus. 



LL. Male forceps, seen from above, gradually narrowed from near base; 

 eighth abdominal segment of female (basal segment of ovipositor) 

 shorter than 6th and 7th together. 

 O. Arista shorter than third antennal joint. 



