128 DIPTERA OF NORTH AMERICA. [PART II. 



upon the first half of the upper side rather strong bristles. Hind 

 tibiae at the root and almost upon the whole second half black, 

 otherwise brownish -yellow and not incrassated. Fore tarsi yellow, 

 somewhat infuscated towards their end, of plain structure, only 

 the first joint upon the under side provided with a few bristles. 

 Middle tarsi brownish-yellow at the basis, further brownish-black ; 

 the first joint has upon the first half of its under side rather numer- 

 ous black bristles. Hind tarsi black, plain. Cilia of the tegulae 

 black. Wings hyaline, only a little tinged with gray. 



Eab. Sitka. (Sahlberg.) 



Observation. — Of this and of the next following species, as also 

 of Argyra cylindrica, I possess only single specimens, damaged 

 by mould, which crumbled to pieces in the attempt of cleaning ; 

 however, as these three interesting species come from a country 

 which is so little explored with regard to Dipterology, and as the 

 important specific characters could be determined, I did not hesi- 

 tate to describe them. I must, however, request not to attach 

 more weight to my statements about color, diffusion of the white 

 tomentum upon abdomen and thorax, and about the appendages 

 of the hypopygium, than the circumstances should warrant. 



3. A. arbiventris, n. sp. % . — Viridis, nitens, abdomine albomi- 

 cante, fronte et facie nigris, albido-pollinosis, pedibus nigris, tibiis om- 

 nibus totis tarsorumque anticorum basi flavicantibus. 



Green, shining, abdomen white, glittering ; front and face blackish, but 

 with whitish dust ; the whole tibiae and the root of the fore tarsi yel- 

 lowish. Long. corp. 0.18—0.19. Long. al. 0.18. 



Metallic-green. Front and face appear, when looked upon in 

 most directions, almost whitish-gray on account of the dust which 

 covers them, but are black. Palpi and proboscis black. An- 

 tennae smaller than those of Argyra nigripes ; the first joint is 

 comparatively short and sparsely beset on the upper side with 

 rather short hairs. Thorax and scutellum shining metallic-green ; 

 but when looked upon from the front, the covering of white dust 

 becomes distinctly visible. Scutellum without hairs. Abdomen 

 covered with a thick dust having a white lustre ; its second and third 

 segments have, on the lateral margin, a large yellow transparent 

 spot. Venter mostly yellowish. The small lamellae of the hypo- 

 pygium are brownish-black. Coxae black ; fore coxoe with long 



