90 PROCEEDINGS OF THE NATIONAL MUSEUM, VoL. 62. 
rest of the frons silvery white and with long black pile. Face 
silvery white pollinose and largely white pilose, the outer margin with 
black pile, this black pile reaching to the black mark on the cheeks 
and crossing it on the underside of the head. Mouth parts blackish 
with white pile. Occiput silvery gray pollinose, thinly so in the 
median portion above, the pile white, post-ocular bristles black and 
slender. Antennae black, the first joint about the length of the third 
(fig. 143), with white pile and black bristles; third joint with minute 
hairs at the base and a short style; first two joints gray pollinose. 
Thorax semishining black, with two very distinct widely separated 
whitish vittae; pile of mesonotum largely erect, blackish, white around 
the margins; scutellum shining black with a silvery pollinose mar- 
gin, four marginal black bristles, the pile white. Pleura and coxae 
gray pollinose and white pilose. Bristles of the thorax long and 
black. Halteres blackish, the stem paler. 
Abdomen shining black; first segment dull, second segment semi- 
shining on the base, the rest of the dorsum silvery pollinose as in 
many species of Psilocephala; sides of segments beyond the third 
shining black. Venter shining black, the first segment gray pollinose, 
the second and third with silvery pollinose posterior margins. Gen- 
italia black, small (fig. 144), the pile almost entirely black. Pile of 
the abdomen long and white on the first segment and sides of the 
others, on the dorsum reclinate and confined largely to the posterior 
margins. Femora black, the front legs entirely black, or reddish at 
the base of the tibiae; the four hind tibiae except apices reddish; 
four hind tarsi reddish at base, black beyond. Wings hyaline, the 
veins blackish brown, stigma brown, cell M-3 closed and petiolate. 
Female.—Length 6 to 7 mm. Very nearly like the male. Frons 
wide below, narrow above, largely shining black, including the vertex 
and ocellar tubercle, smooth, gently convex, the lower corners silvery 
as in some species of Psilocephala (fig. 127); there are a few black 
hairs on the vertex and across the frons above the antennae, Pile 
of the head colored as in the male but shorter, black mark on the 
cheeks broader. 
Thorax and scutellum much as in the male, the pile much shorter; 
the mesonotum with short golden tomentumlike pile, the reclinate 
pile on the scutellum silvery white. Abdomen shining black, the 
first segment gray pollinose on sides and venter, the second and 
third segments with narrow silvery posterior borders, the fifth seg- 
ment with large lateral silvery pollinose spots. Pile on the first 
three segments very sparse, largely on the posterior margins; some 
black pile on the sides of the third, from the fourth segment on black 
erect pilose, the pile longer than is usual in the species of Thereva 
and Psilocephala. Posterior margins of second and third ventral 
