276 Tuer BLOowFutes oF NortH AMERICA 
long as second, orange at base and darker apically and dorsally; 
arista dark brown to black, with long black cilia for four-fifths 
its length; palpus orange, 4.2 in length; back of head rather 
flat above but rounded below, and with three or four rows of 
postocular cilia and abundant tawny hair especially on the 
metacephalon. 
Thorax black, with heavy gray pollen especially anteriorly, 
and with indistinct dorsal longitudinal stripes; hindmost pre- 
acrostichal and dorsocentral bristles placed 2.0 and 1.2, respec- 
tively, before suture; sternopleural bristles usually three, ar- 
ranged 2 + 1, but sometimes with one or more adventitious 
bristles in the series; tympanic ridge with several dark hairs; 
preparapteron orange, with white pubescence, other sclerites 
at wing base black; scutellum as in abina. 
Legs with fore tibia with one posterior bristle, middle tibia 
with one posterodorsal bristle; hind tibia with one anteroventral 
bristle; otherwise like abina. 
Wing hyaline, brown basally; subcostal sclerite orange brown, 
orange pubescent toward base; costal sections 2 to 6 in the pro- 
portion 83:50:125:48:9; fourth vein sometimes with a very 
short spur at angular bend; upper squamal lobe brownish with 
brown rim; lower squamal lobe brown, with whitish rim. 
Abdomen strongly bluish, tessellated, with silvery pollen; 
second segment with marginal row of minute bristles, each suc- 
cessive tergite with stronger and more erect marginal bristles; 
sternites successively wider. 
Genital segments (pl. 26, C and D) as illustrated. 
Female. Head with same proportions as that of male except 
eye shorter, bucca 0.48 eye height; parafaciale 1.4 in width 
opposite lunule; distance between vibrissae 2.4; front with nearly 
parallel margins, 0.38 of head width at vertex and 0.42 at lunule; 
frontale occupying three-fourths frontal width toward middle 
and narrowing anteriorly, velvety black; vertex mostly shining 
black; frontal bristles about five, the rows slightly diverging 
toward lunule and extending almost to middle of second antennal 
segment; back of head rounded. Wing with costal sections 2 to 6 
in the proportion 60:40:100:36:6. Otherwise similar to male 
except for normal sexual differences. 
Length. 6-9 mm. 
Distribution. Nearctic: Alaska, Katmai (August), Naknek 
Lake (July and August), Kodiak (September), and Seward 
(July); United States, Wyoming, Lake Junction, Yellowstone 
National Park (August), Colorado, Pingree Park, (August). 
Biology, habits, and immature stages. Unknown. 
