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440 SUPPLEMENT. 
HYALOMYIA (to follow the genus Acaulona, p. 4). 
Hyalomyia, Rob.-Desvoidy, Essai sur les Myodaires, p. 298 (1830). 
The species of this well-defined genus are often difficult to determine, because their 
bodies, usually of a shining black or somewhat metallic ground-colour, are sometimes 
covered (in the best-preserved specimens) by a greyish or yellowish tomentum, which, 
however, is easily abraded. As to the distinction of the sexes, it must be observed 
that, contrasted with nearly all other Muscide, in Hyalomyia the front of the males 
is broader than that of the females, where it is trigonal with the eyes coalescent or 
closely approximate on the vertex. In the Central-American species this difference is 
still more striking than in the European forms. The foot-claws and pulvilli are of 
the same length in both sexes, or sometimes more elongate in the males. In the 
females the last abdominal segment is convex, bent downwards and ending in a curved 
spine. 
I give here a Synoptic Table of the Mexican Hyalomyie known to me, though 
I am unable to indicate with any certainty the two sexes of the same species :— 
. Front with parallel or nearly parallel sides, as broad as or broader 
than the eyes (males). Yer Ddyeys yt, 2. 
__ Front trigonal (females) . . oe ee se ee 6. 
/ 2. Wings yellowish, the veins, except those near the tip, yellow 3. 
Wings hyaline or partly infuscated with black veins . A 
8. Thorax yellowish-grey, with black lines; wings not infuseated at 
the tip. . . sone - « munda, v.d. Wulp. 
Thorax cinereous, with black stripes ; wings infuscated at ‘the tip . villosa, v. d. Wulp. 
4. Thorax and scutellum yellowish-grey . . . . . . . . . « hebes, v.d. Wulp. 
Thorax and scutellum blackish . . . . . . . .. OS 
5. Front ochraceous . . . soe ee wwe ww we. «OChriceps, v. d. Wulp. 
Front white, with black reflections . » . « , argenticeps, v. d. Wulp. 
6. Wings hyaline, at most slightly infuscated at the base. yo | 
Wings obscure or with infuscated portions . . . oe ew e 8 
7. Front narrowed behind in such a manner that the eyes are nearly 
coalescent. . . . ee - « nigrens, v. d. Wulp. 
Front, though very much narrowed behind, distinctly separating 
the eyes. . . . . - + + « piceipes, v.d. Wulp. 
8. Small cross-vein on the middle of the discal cell (wings uniform 
brown). . . . . . - + + + « merens, v. d. Wulp. 
Small cross-vein beyond the middle of the discal ‘cell rs? 
9. All the veins broadly bordered with brown ... . . umbrosa, v. d. Wulp. 
The brown coloration of the wings more confined, usually forming 
a dilute brownish spot on the mediastinal cell and on the small 
cross-veln . 6 ee 6 ee ee ee we ww ww ee mbrifera, y. d. Wulp. 
