254 DIPTERA. 
A single specimen, which, owing to the short foot-claws and pulvilli, seems to be a 
female; the front, however, is not broader than in C. longiseta. I am in doubt whether 
this is a distinct but closely allied species, or merely the other sex of the preceding. 
THELAIRODES, gen. nov. 
Head hemispherical ; front broad, in the male slightly narrowed behind; face nearly perpendicular, not 
carinated ; vibrissal swellings nearly or quite parallel; vibrisse inserted quite at the oral margin, which 
is not prominent; eyes bare (in one species microscopically pubescent in the male), descending to near the 
lower part of the head. Antenne inserted in a line with the centre of the eyes; third joint much longer 
than the second; arista plumose. Proboscis short, with well-developed terminal lips; palpi cylindrical, 
sometimes slightly thickened towards the tip. Abdomen conical, with only marginal macrochete on the 
segments. Legs slender; foot-claws and pulvilli elongate in the male. Wings longer than the abdomen ; 
third vein with a row of short bristles ; apical cell opened at a little distance before the wing’s tip; curva- 
ture of the fourth vein with a blunt angle and without appendage; posterior cross-vein nearer to the 
curvature of the fourth vein than to the small cross-vein. 
; Allied to the European genus Zhelaira, Rob.-Desv., but differing from it by the absence 
of discal macrochete on the abdomen; and, in Thelairodes vittigera and T. cinerei- 
collis, by the first vein being without bristles. I include in it the following three 
species :— 
1. Palpi black ; larger species (length 7°5 millim. or more). . vittigera, Bigot. 
Palpi yellow; smaller species (no longer than 6°5 millim) . 2. 
2 Legsblack . . 2. 2. 2. 1 we ee eee we  Cinereicollis, v. da. Wulp. 
Coxe and femora yellowish-rufous. . . . . . . . . pallida, v. d. Wulp. 
1. Thelairodes vittigera. (Tab. VI. figg. 9; 9a, head.) 
Homodexia vittigera, Bigot, Ann. Soc. Ent. Fr. 1888, p. 267. no. 72. 
Thorax cinereous, with black dorsal stripes ; abdomen black, the second and third segments with white front 
borders, in the male the first three segments laterally yellowish ; antennz, palpi, and legs black. 
Length 7:5-10 millim. 
Head white, with grey reflections ; front of the male narrowed behind, on the vertex narrower than the eyes, 
that of the female with nearly parallel sides and broader than the eves; frontal band black; behind the 
posterior orbits a row of short bristles; beard white. Antenne black; second joint with short bristly 
hairs; third joint four times as long as the second, rounded at the tip, usually somewhat rufous at the 
base ; arista long-plumose, slightly thickened at the base. Proboscis black, the terminal lips yellowish- 
rufous; palpi black, cylindrical, as long as the proboscis. Thorax and scutellum cinereous ; thoracic 
dorsum with four black stripes—the median ones linear, the outer stripes broad; shoulders and pleure with 
white reflections; base of the scutellum black. Abdomen conical, in the male twice, in the female one 
and a half times, as long as the thorax, shining black, the second segment with a narrow, the third 
segment with a broader, silvery-white front border; in the male the first and second segments and the 
front margin of the third laterally yellowish and transparent; long and stout macrochete are on the 
hind margins of the second and following segments. Middle and hind tibie with some long bristles ; 
foot-claws and pulvilli elongate in the male, the pulvilli yellow. Tegule whitish. Wings grey, brownish 
towards the costa and along the veins, especially in the female; the costa with short cilis and with a 
spine at the end of the auxiliary vein ; third vein with a row of short bristles extending from its origin to 
the small cross-vein, the latter placed before the middle of the discal cell; posterior cross-vein curved. 
Hab, Mexico, Dos Arroyos, Rio Papagaio, Tierra Colorada, Tepetlapa, Amula, 
