94 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
thorax destitute of black pile; knob of halteres brown, margined with yellow; veins 
of wings largely yellow, stigma also yellow and indistinct. 
Female differs from the female of otiosa, besides in the particulars above mentioned, 
in that the front is destitute of the two round velvet black spots, having instead a 
narrow, interrupted, dark-brown crossband; eighth abdominal segment opaque polli- 
nose, its pile largely yellow. 
Length 8tollmm. Los Angeles County, California. Five males and one female. 
C. W. Johnson very kindly loaned the only two specimens of 
this species in his collection; these were the only specimens available 
for examination. Both are males, one labeled ‘‘ Colo. no. 1836” and 
the other ‘ Ft. Collins, Colo., VIII, ‘00.’ The first specimen lacks 
the third joint of each antennae and is scarcely distinguishable from 
the male of candidata, the bristles of the occiput being black. The 
other specimen is about 11 mm. in length and has a very characteris- 
tic third antennal joint, the base bulbous and black, the apical half 
very slender and yellow, with a short black arista (fig. 139); the first 
joint is shorter than the third, white pilose, and with a few black bris- 
tles at the tip. The specimen has been wet and considerably rubbed. 
The knob of the halteres is not black at the base as in candidata, but 
yellowish. Vein R 1 is brown, the other veins yellow. The femora 
are black to the tips. 
THEREVA VIALIS Osten Sacken. 
Plate 10, fig. 129; plate 11, figs. 140 and 147; and plate 12, fig. 158. 
1877. Thereva vialis OstEN SAacKkEN, Bull. U. S. Geol. Surv., vol. 3, p. 274. 
This common western species was described from males only. It 
is very near candidata Loew of the Eastern States, but differs in hav- 
ing black pile near the antennae, the femora black to the tips, and 
the wing veins darker. 
Type locality.—Y osemite Valley, California. 
Type.—In the Museum of Comparative Zoology at Cambridge. 
Allotype.—I have designated as a neallotype a specimen taken at 
Stanford University, April 30, 1920 (Cole). This specimen is depos- 
ited in the United States National Museum. 
Female.—Length 8to10 mm. Upper two-thirds of frons yellowish 
brown pollinose, with two large rounded velvet black spots, which 
almost touch in the middle (fig. 129); lower frons and face silvery 
white pollinose; the pile of upper frons short, black, that of the lower 
frons, face, first antennal joint, and occiput yellowish. Antennae 
black, the first joint about as long as the third, the style short; first 
and second joints gray pollinose. Occiput white pollinose, the pile of 
lower occiput and cheeks white. 
Thorax black, the mesonotum dark-gray pollinose, with two pale 
vittae, yellowish reclinate pile and a few erect black hairs. Scutellum 
and pleura gray pollinose, center of scutellum darker; pile of scutellum 
