106 PROCEEDINGS OF THE NATIONAL MUSEUM, VOL. 62. 
the remainder short, erect, and yellowish. Base of first, second, 
third, and fourth segments broadly blackish gray and destitute of 
pollen, a very narrow border on the fifth; a narrow brownish pos- 
terior margin on the fifth, sixth, and seventh segments, the eighth 
wholly brownish. 
Type locality.—Golden Gate Park, San Francisco, California, June 
6, 1921 (EK. P. Van Duzee). 
Type.—Male and allotype female, in California Academy of 
Sciences; there are several paratype males and females taken at the 
same place on June 15, 1921 (Cole); a pair of these are deposited in 
the U.S. National Museum, No. 25939. There are two males in the 
collection of the California Academy of Sciences, one taken with the 
types and one July 10, 1920 (KE. P. Van Duzee). 
The species is named for E. P. Van Duzee, who made the trip 
to Golden Gate Park with the writer and collected the first specimen. 
The species is probably local, being confined to the great sand- 
dune country around the edge of Golden Gate Park. Some of the 
specimens were taken on the wind-swept areas some distance from 
any vegetation. In no other species examined has there been found 
such a variation in vein M~-1 and M-2, cell M—2 being peticlate in 
some specimens and broadly open in others. In one female the cell 
first A is narrowly open and there is an adventitious cross vein in 
the cell first M-2. 
THEREVA NIVEIPENNIS Kréber. 
Plate 11, fig. 134, and plate 12, fig. 160. 
1914. Thereva niveitpennis Kr6seER, Beiheft z. Jahrb. Hamb. Wiss. Anstalten, 
vol. 31, p. 66. 
Male.—Length 9 mm. A species closely allied to vanduzeei. Head 
grayish white pollinose and largely white pilose, a few black hairs on 
the upper corner of the frons, and the pile of the ocellar tubercle 
black. Post-ocular bristles yellow, but there are two black bristles 
near the middle and some distance from the eye margin; the pile of - 
this upper portion of the occiput yellow. Antennae black, the first 
two joints gray pollinose, with whitish pile and bristles; third joint 
almost as long as the first two combined, the arista short. (Fig. 134.) 
The larger part of the mesonotum brownish pollinose, with two 
wide whitish vittae; the median brown stripe inclosed by these has 
a darker central portion, widened in the middle; mesonotum with 
erect white and reclinate yellowish pile, the reclinate pile on the 
lateral margins, however, and before the scutellum silvery white. 
Scutellum gray pollinose with a dark-brown basal spot and erect 
dark-yellow pile; there are four marginal bristles. Pleura gray polli- 
nose and white pilose. Stem of the halteres yellow, the knob 
blackish brown. 
