ART. 10 TROPICAL AMERICAN DIPTERA VAN DUZEE 39 



In Doctor Aldrich's table of genera in Williston's Manual of North 

 American Diptera this would run to Plagianeurus; in that genus the 

 cross vein is far from the wing margin, the dorsocentral and post- 

 ocular bristles are large, in this all these bristles are wanting in both 

 fiexes, except the hairlike dorsocentrals. 



The name is suggested by the thickened posterior legs of the male. 



Type of genus. — Oedematopus crassitibia, new species. 



OEDEMATOPUS CRASSITIBIA, new species 



Male. — Length 4.5 mm.; of wing 6 mm. Face, front, and palpi 

 covered with silvery white pollen; front about one-fourth as long 

 as the face, rather narrow, being about as wide as the lower part of 

 the face ; face a little narrowed above, but wide even at the antennae, 

 the ridge separating the upj^er and lower portions of the face dis- 

 tinct and a very little below the middle, lower part nearly round, the 

 lower edge evenly rounded and reaching slightly below the lower 

 corner of the eyes; palpi large, longer than wide, almost pointed 

 at tip, the inner edge almost straight, outer rounded, the black 

 ground color showing through the white pollen a little, there are 

 small black hairs near the tip, lying close against the large, black 

 proboscis; antennae rather small, first joint bare above, second with 

 short bristles, third rounded, about as long as wide ; arista bare, dor- 

 sal, more than twice as long as the antennae ; occiput blue with green 

 reflections above, dulled with white pollen; about six black orbital 

 bristles on upper orbits ; beard scattering, yellowish ; no postvertical 

 bristles; one pair of short, straight ocular bristles. 



Thorax green, not shining, even the posterior part dull, the anterior 

 portion and most of the dorsum appear velvety blackish brown when 

 viewed obliquely; the sides above the pleurae, from the root of the 

 wing, extending upward at the suture and including the humeri are 

 blue and thickly covered with white pollen; on each side above and 

 inside of the humeri, but quite widely separated from them, is a long 

 silvery-white poUinose spot, which is nearly round, from the inner 

 side of which is a narrower white poUinose stripe extending back 

 parallel with the middle of the dorsum ; the pollen forming this stripe 

 is white but not silvery and fades out posteriorly near the middle of 

 the dorsum ; pleurae green with white pollen ; scutellum blue with a 

 pair of moderately long slender bristles ; metanotum blue with white 

 pollen; one short humeral bristle; no acrostichal bristles; several 

 small slender hairs represent the dorsocentral bristjes ; there are two 

 longer bristles on each side above and back of the root of the wing. 

 Abdomen (fig. 77) formed about as in Hydrophoms., short and 

 thick, without bristles and covered on the side with white pollen ; it 

 is black with green and blue reflections, sometimes quite bright on 

 upper surface and sometimes almost wholly dull black. The hypopy- 



