Ant. 4, REVISION OF THE FAMILY THEREVIDAE—COLE. 29 
erect bristles near posterior margin and usually four short, erect 
black bristles. Pleura black, gray pollinose, thinly white pilose, the 
pteropleura largely shining. Knob of halteres brown, the stem 
yellowish. 
Abdomen black, the dorsum mostly silvery pollinose with short 
white pile, longer at the sides of the first segment; second segment 
with a silky white posterior border; segments 1, 4, 5, and 6 more 
blue-gray pollinose; the last three segments very short, their combined 
length less than that of the second and about equal to that of the 
third; these segments shining blackish with yellowish pile. Geni- 
talia reddish yellow with golden yellow pile, the upper forceps deeply 
excavated and projecting beyond the lower. There is black pile on 
segments 3 to 6 of the venter. Femora blackish brown; hind 
tibiae brown, the anterior ones yellowish brown; fore tarsi enlarged 
and blackish, the first joint of other tarsi and base of second yellowish, 
the rest brown. Wings hyaline, the apex pale grayish, much shorter 
than in the female; costal cell and veins at base of wing yellowish, 
the stigma pale brown; cell M-3 closed and petiolate. 
Female.—Length 8 to 10 mm. Closely resembling the male in 
most characters. Almost bare of pile. Frons narrow, the upper 
half shining black, the lower gray-white pollinose; between the colors 
a diamond-shaped spot, velvet black in color, in some specimens 
rounded below and pointed above. 
Tomentumlike pile of thorax shorter than in male. Mesonotum 
with two faint gray-blue vittae, on either side a more whitish stripe 
bodering the opaque black one over the humeri. The short bristles 
of the scutellum quite variable, two, three or four being present and 
these often differing in size. Halteres light yellowish brown, the 
tips of the knobs darker. 
Abdomen black, semishining; pile on two basal segments whitish, 
beyond with usual short, black, erect pile on dorsum and venter. 
Genitalia reddish yellow with a yellowish circlet of bristles. Legs 
colored about as in the male; fore tarsi blackish with many short, 
black, bristlelike hairs, and enlarged as in the other sex. Wings with 
crossbands more definite than in the male (see fig. 29); cell M-3 
closed and petiolate. 
Type locality.—District of Columbia. 
Type.—tIn the Museum of Comparative Zoology at Cambridge. 
Distribution.—The following localities are given for two males and 
three females: 
North Carolina: Black Mountains, June [Amer. Mus.]. 
New York: Van Cortland, June 22 and July 11 (J. L. Zabriskie), 
[Amer. Mus.]; Mosholu [Amer. Mus.]. 
Krober gives New York and Brazil for the male and adds a record 
from Paraguay for the female. 
