arr. 4. REVISION OF THE FAMILY THEREVIDAE—COLE. 129 
THEREVA SENEX Walker. 
1848. Thereva senex WALKER, List Dipt. Brit. Mus., vol. 1, p. 224. 
The original description by Walker is as follows: 
Female.—Cinerea, capite pectoreque canis, abdomine fasciis ferrugineis, basi piceo, 
sigmenti 2i margine postico cano, antennis pedibusque cinereis, tibiis fulvis, tarsis 
piceis basi fulvis, alis limpidis. 
Head hoary, thickly clothed with white hairs, dark brown between the eyes, 
behind which there are two or three rows of black bristles; eyes and eyelets red; 
feelers gray; the first joint furnished with black bristles; mouth piceous: chest gray, 
thinly clothed with short yellow hairs, and having a few black bristles on each side; 
breast hoary, more thickly clothed with long white hairs: abdomen gray, clothed 
with short yellow hairs, which are most thick at the sides of the segments at the base; 
hind borders of the segments ferruginous; first segment piceous; hind border of sec- 
ond segment hoary; hips and thighs gray, the former thickly clothed with long white 
hairs, the latter more thinly furnished with short yellow hairs, and having also a few 
black short bristles; tips of thighs tawny; shanks tawny, with piceous tips, beset 
with very small black hairs and long black bristles: feet piceous, clothed with short 
black hairs, and having also black bristles at the tip of each joint; first and second joints 
tawny, excepting their tips; wings colorless; brands tawny, very narrow; veins tawny 
along the fore borders, piceous along the hind borders; poisers tawny, piceous toward 
the tips of the stalks; knobs yellow. Length of the body 5 lines, of the wings 8 lines. 
a. Nova Scotia. “From Lieutenant Redman’s collection. 
Major Austin notes that the type in the British Museum is in fairly 
good condition and that the species is apparently a true Thereva. 
THEREVA NIGRA Say. 
1823. Thereva nigra Say, Journ. Acad. Nat. Sci. Phila., vol. 3, p. 40. 
1882. Psilocephala nigra VAN DER Wutp, Tijd. v. Ent., vol. 25, p. 118. 
Say’s original description is as follows: 
Black, incisures and lateral spot on the fifth segment gray. 
Inhabits Pennsylvania. 
Head glabrous, polished; hypostoma and all beneath with gray minute hair; 
antennae with minute gray hair, and longer sparse black hair on the basal joint; 
occiput velvet black; wings pellucid, stigmata and nervures brown, costal edge 
beyond the stigma pale, each of the two ultimate pairs of nervures uniting before 
they attain the edge of the wing; poisers brown; scapus pale; pleura, pectus, and 
coxae somewhat glaucous; feet blackish, tibiae and tarsi excepting at tip pale, 
anterior tibia at tip and tarsi blackish; tergum polished, posterior edges of the third 
or fourth basal segments gray, spot each side of the fifth segment oblong-oval oblique. 
Length 0.3 of an inch (about 8 mm.). 
The type is destroyed and it is probable that the identity of this 
species will never be known. Coquillett considered it a true Thereva, 
and various species of Psilocephala and Thereva have been placed 
under the name by other dipterists. The description sounds like a 
Psilocephala related to haemorrhoidalis and prehaps Kréber is correct 
in his supposition that Say had before him what we now know as 
Psilocephala haemorrhoidalis when he described this species. 
