130 DIPTERA OF NORTH AMERICA. [PART II. 



the feet are not entirely black ; the fore femora have upon the 

 hind side more, the hind femora on the under side less numerous 

 blackish hairs of greater length. Fore tarsi not infuscated ; the 

 first joint has scarcely 1^ the length of the four following joints 

 put together. Only the last joint of the middle tarsi is somewhat 

 infuscated. The first joint is fully as long as the others together. 

 The last joint of the hind tarsi is brown ; the first joint is of sim- 

 ple structure and beset with the usual short hairs, scarcely a little 

 longer than the second, but considerably thicker. Cilia of the 

 tegulffi yellowish-white. Wings hyaline, scarcely a little tinged 

 with yellowish-gray, with brownish-yellow veins ; the last segment 

 of the fourth vein is very abruptly bent forward before its middle. 

 Hob. District Columbia. (Osten-Sackeu.) 



5. A. calcitraiHS LOEW. ^ . Scutello c nudo, pedibus totis pallide 

 flavicantibus, metatarso postico maris paulo incrassato et valde liirto. 



Scutellum bare ; the whole feet pale-yellowish ; the first joint of the hind 

 tarsi of the male somewhat thickened and covered with rough hair. 

 Long. corp. 0.14 0.15. Long. al. 0.11. 



SYN. Argyra calcitrans LOEW, Neue Beitr. VIII, 46, 3. 



Male. Face narrow, silvery-white. Thorax and proboscis 

 black. Antennas black, third joint more blackish-brown ; arista 

 distinctly inserted before its end. Front silvery-white. Cilia of 

 the upper orbit black, very short and delicate ; cilia of the inferior 

 and lateral orbits white. Thorax shining green, covered with 

 thick white dust, so as to make the ground color invisible in some 

 directions. Scutellum also shining green, or blue-green, with 

 less dust, and bare with the exception of the usual bristles. The 

 ground color of the abdomen seems to be blackish-blue, but cannot 

 be distinctly seen on account of the thick white dust which covers 

 it ; the second segment is yellowish and transparent, with a black- 

 ish border on the posterior margin and with a blackish middle 

 line, which is sometimes wanting ; the third segment is of a simi- 

 lar color, only the margin on the posterior border and the middle 

 line are broader, though the latter is sometimes interrupted. The 

 email lamellae of the hypopygium are brown. Coxaa and feet 

 white-yellowish ; fore coxaB with delicate white little hairs .and 

 delicate black bristles ; middle coxae on the outside with a black- 

 ish spot ; hind coxa? scarcely a little blackened on the extreme 



