1923 ] 
The Genus Lasiopogon 
137 
spots, the gray of hind margins extending triangularly 
between them ; heavily pollinose and quite pilose. (Wash.) 
ripicola, n. sp. 
Small species of 7 to 9 mm 8. 
8. Nearly bare species; abdominal segments with narrow 
white pruinose fascia along hind margin; thorax tri- 
vittate with brown. (Wash.) trivittatus, n. sp. 
A great deal of white pile on body; the paler hind portion 
of abdominal segments extending forward along the 
middle; thorax bivittate. (Cal.) drabicola Cole. 
9. Tibiae and tarsi reddish-brown; wings quite infumated; 
halteres with black spot on knob ; abdomen dull, the pos- 
terior two-fifths of each segment with gray fascia, 
(mountain species. Wash.) fumipennis, n. sp. 
Legs black in ground-color; wings nearly hyaline 10 . 
10. Thorax evittate; hypo pygial valves polished; small species, 
6 to 8 mm 11 . 
Thorax vittate 12 . 
11. Mesonotum uniformly brown pollinose; hypopygial valves 
twice as long as wide, with strong projection below near 
base, dorsal fringe black. (Wash.) delicatulus, n. sp. 
Mesonotum brownish gray pollinose; valves short, very 
convex, almost hemispherical, dorsal fringe reddish. 
(Mass, to Col.) opaculus Loew . 
12. General color gray pollinose; hypopygial valves cinereous, 
about three times as long as wide, without basal prong or 
swelling, (on stones about streams, Or., Wash.) 
cinereus Cole 
General color brownish pollinose; hypopygial valves pol- 
ished, or of tetragrammus grayish-brown pruinose 13 . 
13. Space between intermediate and lateral stripes of thorax 
polished black; ovipositor white pilose; about four cons- 
picuous bristles across each abdominal segment. (Can., 
N.H.) tetragrammus Loew 
Thorax without shining stripes; no transverse rows of 
bristles on abdominal segments, (western species) 14 , 
