38 PROCEEDINGS OF THE NATIONAL MUSEUM vol.74 



Thorax bright green, the depressed space before the scutellum cop- 

 pery ; abdomen bhie-green ; bristles of the thorax and the minute hairs 

 on the abdomen yellow ; the very .small bristles on the hind margins 

 of the abdominal segments and the bristles of the head black. Hy- 

 popygium (fig. 53) black with purple reflections, truncate at tip, its 

 lamellae pale yellow, brown at tip, large and with the tip drawn out 

 into a point, there are three or four long hairs on upper edge. 



All coxae brown with yellow tips; femora, tibiae and tarsi pale 

 yellow, tarsi scarcely darker at tip ; joints of middle tarsi as 20-11- 

 T-5-4; of posterior pair as 12-17-10-6-6, 



Wings a little grayish, veins yellowish brown; fourth vein only 

 slightly bent back at the cross vein, ending in the apex of the wing; 

 fifth vein nearly straight; cross vein 8, last section of fifth vein 

 twenty-five fiftieths of a millimeter long. 



Described from one male, taken by J. M. Aldrich, May 1, 1926, at 

 El Salto, Antigua, Guatemala. 



Type.— C2it. No. 41051, U.S.N.M. 



This differs from amoenus Becker (Bolivia) in having the hy- 

 popygial lamellae pointed at tip with several long hairs below, in 

 amoenus they are also pointed, but with a long filament at tip. From 

 picaillus Aldrich it differs in having all coxae blackened and in not 

 having any inner appendages visible. 



OEDEMATOPUS, new genus 



This belongs to the Hydro'phoTinae. It differs from Liancalus in 

 having no long bristles near the posterior margin of the abdominal 

 segments and also in having the fore femora a little thickened at 

 base, as in Scellus and Hydrophoms. It differs from the last two 

 genera in having only fine hairs on lower surface of fore femora in 

 both sexes. It differs from all three genera in having the posterior 

 cross vein and last section of fourth vein nearly in the same line and 

 both nearly parallel with the posterior margin of the wing. 



The face is wide, reaching to or a little below the lower margin of 

 the eyes; first antennal joint bare above; arista dorsal, nearly bare; 

 palpi large in both sexes; proboscis large; one pair of ocellar bristles. 

 No acrostichal bristles; dorsocentrals reduced to small hairs before 

 the suture ; scutellum with one pair of large marginal bristles, which 

 are convergent; there are two bristles of considerable size above the 

 root of the wing. Abdomen and the hypopygium of the male formed 

 about as in the genus Hydrophor-us; femora and tibiae without 

 bristles in the male, with a few small ones in the female ; base of the 

 fore femora a little enlarged; first joint of hind tarsi a little longer 

 than second. Last section of fifth vein very short, cross vein long, 

 nearly six times as long as last section of fifth vein; sixth vein 

 present. 



