186 DIPTERA OF NORTH AMERICA. [PART II. 



they bave their greatest breadth somewhat before their middle ; 

 the posterior transverse vein is in the middle between the extreme 

 root and the tip of the wings ; the first longitudinal vein runs at 

 least as far as the third of the length of the wing. , 

 Uab. Middle States. (Osten-Sacken.) 



6. ©• leucostomus Loew. % and J . — Laete viridis, thorace et 

 scutello interdum caerulescentibus, tegularum ciliis a-lbidis, vena longi- 

 tudinali quarta non inWrupta. 



Light green, thorax and sentellum sometimes more blue ; cilia of the 

 tegulse whitish, the fourth longitudinal vein not interrupted. Long, 

 corp. 0.09—0.10. Long. al. 0.12. 



Syn. Diaphorus leucostomus Loew, Neue Beitr. VIII, 58, 5. 



Male. Light green, metallic, shining, thorax and scutellnm 

 sometimes sky-blue. Face for a male very broad, deepened length- 

 wise, without transverse swelling, so thickly covered with snow- 

 white dust, that the ground-color becomes invisible. Palpi 

 protruding, much larger than in the males of other species ; 

 proboscis very small, black. Antennae black, larger than in other 

 species ; the third joint is particularly distinguished by its more 

 considerable size and is extended at the end into a short point ; 

 arista inserted on the upper side before the tip of this point, but 

 so much bent downward as to be easily mistaken for being apical. 

 Front of uniform breadth, scarcely exceeding that of the face, 

 blue with white dust, which is thicker near the antennas and is 

 almost totally wanting upon the vertex. Cilia of the upper orbit 

 black, those of the lower and lateral orbits whitish. Thorax with 

 thin gray-whitish dust. The bristles on the posterior margin of 

 the small hypopygium rather long and strong ; its outer appen- 

 dages are not distinctly visible. Coxae black, the foremost dusky- 

 whitish at the tip, on the front side rather bright blue-green and 

 fringed with whitish hair, but without black hairs or bristles. 

 Femora metallic blue-green with yellowish tip, with very short 

 hair. Tibiae and tarsi yellowish, the latter towards the end gradu- 

 ally somewhat darker, but only their last joint brown ; fore tibiae 

 without strong bristles, middle and hind tibiae with a stronger 

 bristle on the exterior edge of their upper side and not far from 

 the root ; the hind tibiae, on the exterior edge of the upper side, 

 are sparsely beset with shorter and weaker bristles. Fore tarsi 



