188 DIPTERA OP NORTH AMERICA. [PART II. 



the second ; the following joints are, in the female, of decreasing 

 length ; in the male the third joint is somewhat shorter than the 

 fourth, and at its end, on the posterior side, beset with longer 

 black hairs. Wings towards the basis very much narrowed ; the 

 posterior transverse vein is before the middle of the disk of the 

 wing, but rather exactly in the middle between the extreme root 

 and the tip of the wing ; the fourth longitudinal vein ends some- 

 what before the extreme tip- of the wing ; in the female, however, 

 at a very small distance from it. 

 Nab. Sitka. (Sahlberg.) 



II. THE FOURTH LONGITUDINAL VEIN ENDING INTO THE TIP OF 



THE WING. 



2. S. frontalis LOEW. and 9 . Nigricans, fronte Isete violaceo 

 splendente, antennis totis nigris. 



Blackish. ; the front bright violet ; the antennae entirely black. Long. 

 corp. 0.11. Long. al. 0.12 0.13. 



. Sympycnusfrontalis LOEW, Neue Beitr. VIII, 67, 1. 



Face in the female of moderate breadth, in the male below very 

 narrow, towards the antennae broader, with white dust, so that 

 the blue ground-color becomes very little visible. Antennae 

 black, larger than in the next following species ; the first joint 

 rather long ; the third joint only with "a very short pubescence, 

 larger and ovate in the male, smaller and rather rounded in the 

 female. Front bright steel-blue or violet. Cilia of the inferior 

 orbit whitish. Upper side of the thorax dull on account of a thick 

 gray-brownish dust, nevertheless the green or blue ground-color 

 is distinctly visible through the dust. The scutellum is of the 

 same color as the upper side of the thorax, and has no hairs 

 besides 'the usual bristles. Abdomen black or greenish-black, 

 the second segment usually with a complete or almost complete 

 yellowish transparent transverse band, the third segment with 

 one, which is interrupted in the middle ; moreover the first and 

 fourth segments are usually yellowish-transparent on the lateral 

 margin. The venter is always white-yellowish. The hypopygiurn, 

 of the same color as the abdomen, is somewhat larger than in the 

 other species of this genus known to me, and but very little im- 

 bedded ; its outer appendages are so small and hidden that I can- 

 not distinctly perceive their shape. The posterior margin of the 



