AMERICAN DIPTERA. 53 



each side ; third segment with a similar vitta, but not at all widened anteriorly^ 

 truncate instead, posteriorly widened in a similar manner to that on second seg- 

 mer.t, but less so ; fourth segment with a black subtriangular marking, truncate 

 anteriorly ; posterior borders of second and third segments reddish, very narrowly 

 yellowish on the edge, that of fourth segment more yellowish ; venter red, black- 

 ish at base in middle. Legs black, knees of anterior and middle pairs yellowish. 

 Wings subfuscous, nearly hyaline, stigma flavous. The first posterior cell is more 

 broadened and shortened, the last section of fourth vein bulging out more. 



Fort Collins, Colorado (Gillette). One female. 



It may at once be known from T. qnadrata by it? red abdomen 

 and shining black face, combined with the absence of a yellow border 

 on the scutellum. 



66. Tropidia quadrata Say. 



Washington, D. C, May 19. One male. The posterior band of 

 second segment is wholly reddish yellow, brownish at lateral ends ; 

 rest of liglit color of segment yellow, leaving only an opaque black 

 T, which is not inverted, and the bar of which extends on hind bor- 

 der of first segment. Third segment with the opaque, black, median 

 vitta abbreviated on more than its posterior half, lapsing into reddish 

 yellow, which spreads along hind margin of segment. 



67. Xylota clialybea Wied. 



Washington, D. C, May 22. One male. Length 14 mm. Dor- 

 sum of thorax and scutellum with a strong violet shade. 



68. Xylota flavitibia Bigot. 



Fort Collins, Colorado (Gillette). One male ; pleura and scutel- 

 lum with longer whitish pile than dorsum of thorax, which is thinly 

 pilose. First abdominal segment wholly black, apparently without 

 red hind angles ; but the anterior angles of the red second segment 

 appear to be very acute and to fill the place of the hind angles of 

 the first, which seem cut off or rounded. The brownish of front and 

 middle tibiae is not very noticeable. Wings hyaline, only the stigma 

 pale yellowish. 



69. Xylota pigra Fab. 



Washington, D. C, May 22. One female ; scutellum concolorous 

 with thoracic doi'sum. Black of second segment faintly apparent in 

 a median vitta on third, and even on base of fourth ; ovipositor ex- 

 serted, very long, curved under abdomen, pale brownish, not orange 

 like the fifth segment, from which it is protruded ; fifth segment sub- 

 triangular, very narrow behind ; ovipositor consisting apparently of 

 three segments. 



TRANS. AM. ENT. SOC. XXII. MARCH, 1895. 



