156 DIPTERA. 
Proboscis and palpi black. Thorax and scutellum black; thoracic dorsum with white reflecting spots on 
the shoulders and immediately before the transverse suture. Abdomen cylindrical (3) or ovate (2), 
shining black, the second and following segments with whitish front margins ; in the male with long discal 
and marginal macrochete, the ventral surface and the anal segment densely clothed with long black 
hairs, and the genitals conspicuous; in the female the macrochete and hairs are shorter. Legs black— 
in the male long and slender (the front tarsi longer than the tibie), the middle and hind tibie with some 
long bristles, the foot-claws and pulvilli elongate, the pulvilli yellowish, but partly obscure; in the 
female shorter, the tarsi, foot-claws, and pulvilli not elongate. Tegule yellowish (3) or white (9). 
Wings of the male brownish, more intense towards the costa, those of the female greyish, a little more 
obscure on the costa; small cross-vein nearly on the middle of the discal cell; apical cell narrowly 
opened at the wing’s tip; curvature of the fourth vein arcuate; apical cross-vein very slightly concave ; 
posterior cross-vein straight, nearly in the middle between the small cross-vein and the curvature of the 
fourth vein. 
Hab. Mexico, Omilteme in Guerrero 8000 feet (H. H. Smith). 
In its general facies (the narrow front, the elongate body and legs, the hairy abdomen, 
&c.) the male differs from the corresponding sex of the other species of the genus; the 
female, on the contrary, has the usual aspect. That they are indeed the sexes of the 
same species seems to be proved by the particular markings of the thorax, which are 
quite similar and not present in any of the other members of the genus. 
M. Bigot has characterized the following Central-American species of Degeeria, but I 
cannot recognize in them any of the species here described. 
Degeeria cora, Bigot, Ann. Soc. Ent. Fr. 1888, p. 259. no. 29.—Mexico. 
anthracina, Bigot, loc. cit. no. 30.—Mexico. 
DIDYMA, gen. nov.* 
‘Small, blackish species. Head hemispherical ; front scarcely prominent, moderately broad, in the male usually 
narrowed behind ; frontal bristles descending on each side in a single row beneath the root of the antenne ; 
face perpendicular or slightly inclined; facial ridges fringed with bristles; vibrissee inserted at the oral 
‘margin, which is not prominent. Eyes pilose. Antenne nearly as long as the face; their basal joints 
short; third joint at least four times as long as the second; arista bare, not visibly jointed. Proboscis 
slightly exserted ; palpi cylindrical or filiform. Abdomen conical or elliptical; basal segment as long as 
the following segment; the segments with marginal, sometimes with discal and marginal, macrochete. 
Legs bristly ; foot-claws and pulvilli short in both sexes. Wings longer than the abdomen ; apical cell 
narrowly opened, ending at a very little distance above the wing’s tip; curvature of the fourth vein with 
a blunt angle; posterior cross-vein in the middle or a little beyond the middle between the small cross- 
vein and the curvature of the fourth vein. : 
This genus is very nearly allied to Degeeria, but differs from it in the hairy eyes. 
From the smaller species of Phorocera, Didyma is distinguished by the apical cell 
ending close to the wing’s tip. Eighteen species are referred to it, all from Mexico :— 
1. Thorax black, without stripes . . 2. . 2... Q, 
Thorax with whitish or greyish tomentum, and more or less 
distinct stripes . . 3. 
e « s e € 
* didupos (twin). 
