SYNOPSIS OF NORTH AMERICAN SYRPHID^. 167 



tiguous. Face distinctly concave below the antenna). Thorax clothed 

 with long and dense sulphur-yellow pile; from above, the ground color 

 appears black. Scutellum wholly yellow, densely yellow pilose. Ab- 

 domen with abundant, long, reddish-yellow pile ; first segment black, 

 second segment broadly shining reddish-yellow, in the middle opaque 

 black, the black is broad iu front, behind it occupies less than a fourth 

 of the width of the segment ; third segment of the same reddish-yellow 

 color, shining; the median broad black stripe, continuous with the 

 black of the second segment, is opaque in front, shining behind ; fourth 

 segment similar to the third, but the black wholly shining ; hypopygium 

 shining black. Legs black, with black pile ; tibiie yellowish at the 

 base. Wings nearly hyaline ; stigmatic spot dark brown ; a broad, dis- 

 tinct, brownish spot in the middle of the wing. 



One specimen, Como, Wyoming, altitude 7,000 feet. 



It is probable that the amount of yellow on the abdomen may vary, 

 especially on the third and fourth segments. 



Eristalis occidentalis. 



Erhlalis occidentalis Williston, Proc. Am. Phil. Soc, xx, 222. 

 Habitat. — Washington Territory ! 



$ ,9 . Length, 10 to 12™™. Allied to Bantardi and montanus. Face 

 clothed with reddish-yellow pile and pollen, not at all concave below 

 the autennal process; median stripe and cheeks bare, shining black. 

 Antennae black ; arista red, pubescent near the base. Eyes pilose ; con- 

 tiguous for a short distance ( S ). Front in the female a little narrowed 

 above ; thickly yellowish polliuose and with abundant yellow pile, near 

 the vertex black. Thorax opaque black, with long yellow pile, appar- 

 ently more abundant in the male, but not concealing the ground color 

 when seen from above ; in the female on the front part in the middle 

 with two narrow grayish stripes, abbreviated posteriorly. Scutellum 

 yellow, with more abundant yellow pile. Abdomen black, with abun- 

 dant, rather long, yellow pile ; first segment black ; second broadly 

 yellow on the sides, the black opa-que portion broadly along the front 

 margin, a third of the width of the segment behind ; third segment yel- 

 low on the sides, with a shining interrupted transverse fascia, the black 

 elsewhere opaque ; fourth segment shining black with a small opaque 

 spot in front, sometimes reddish on the sides in front; second, third, 

 and fourth segments with a narrow yellow hind margin. In the female 

 the yellow is apparently less extensive ; on the second segment forming 

 large triangular spots ; on the third nearly or quite wanting, the shin- 

 ing- fascia entire. Legs black ; base of all the tibiai whitish-yellow, the 

 first two joints of the middle tarsi yellowish. Wings hyaline; a dis- 

 tinct brownish spot at the middle. 



Six specimens, Washington Territory. 



This species is evidently variable in the abdominal markings. It 

 must be allied to irilosus from Greenland, though certainly different. 



