ART. 4. REVISION OF THE FAMILY THEREVIDAE—COLE. 33 
Abdomen yellowish red, darker toward the tip; venter the same 
color; posterior margins of third, fourth, fifth, and sixth segment of 
dorsum blackish; circlet of spines on the genitalia and most of the 
short pile yellowish; the short erect pile of segments four to seven 
black, some black pile at base of eighth. Coxae and femora yel- 
lowish, the hind coxae with short apical spines; tibiae brownish 
yellow, the front pair darker apically; front tarsi blackish, the others 
paler. Wings with much the same venation and marking as in L. 
scutellaris Loew (fig. 27); the costal cell and stigma yellowish; a 
large part of the wing infuscated, the extreme apex, a subapical, and 
a median band whitish hyaline. 
Type locality.—Macdona, Texas, July 29, 1911 (H. A. Wenzel). 
Type-—A female. In the Philadelphia Academy of Natural 
Sciences. 
Only the unique type is known. It is closely related to the other 
species of the genus and very probably has its center of distribution 
in Mexico or Central America. 
Genus PSILOCEPHALA Zetterstedt. 
1838. Psilocephala ZETTERSTEDT, Ins. Lappon. Dipt., p. 525. 
Usually small or medium sized species. Head nearly semicircular, 
the frons more vertical than horizontal, thus differing from Nebritus 
and Metaphragma; occiput well developed, but the cheeks rather 
narrow. Antennae porrect and set on more or less of a protuberance, 
varying greatly in shape and size in different species, but never longer 
than the head; the first joint often quite large, the second always 
short, the third usually longer than the first and with a more or less 
apparent apical style; the first two joints with bristles and hairs. 
The males are holoptic, the eyes of the female widely separated. The 
frons of the female may be entirely pollinose, may possess two black 
spots or be largely shining black, the markings being of specific value. 
Kroéber includes a few species in the genus in which the eyes of the 
male are narrowly or even widely separated, and there is one North 
American species, P. latifrons, placed provisionally in thisgroup. The 
face is bare and usually silvery pollinose; palpi club-shaped and long 
pilose; the mouth parts are rather large. 
The thorax is oval, seldom very convex, often quite thickly erect 
pilose in the male, as a rule sparsely reclinate pilose in the female. 
There is a remarkable uniformity in the chaetotaxy of Psilocephala 
and Thereva, the specific variation being little, if any, and yet there 
is a great deal of individual variation. The praesuturals and supra- 
alars are present, one postalar and one or two pairs of praescutellar 
bristles. The scutellum is of medium size, semicircular, and with one 
or two pairs of marginal bristles. The metanotum is small, bare, and 
almost concealed by the scutellum. 
