OSTEN SACKEN ON WESTERN DIPTERA. 337 



and the triangles; a narrow, shining, triangular space between the last 

 cross-band and yellowish-white posterior margin of the segment, which 

 bears a fringe of pale golden-yellow hairs; the third and fourth segments 

 have the same pale yellowish posterior margin and the golden fringe 

 upon it ; on the fourth, however, the fringe is broader, and takes in the 

 whole posterior half of the segment ; on the posterior half of the third 

 segment, there is on each side an elongated velvet-black spot; the 

 anterior margin of this segment has a narrow, pale border, as if prolong- 

 ing the hind margin of the preceding segment ; hypopygium black. 

 Legs black; tip of the femora and anterior half of the tibiae yellowish- 

 white; on the middle pair, three quarters of the tibise and the base of 

 the tarsi are of a pale color. Wings hyaline ; stigma small, brown. . 



Female. — Front broad and rather convex, grayish-pollinose, beset with 

 a dense grayish-white down; vertex a little darker; no velvet-black spots 

 on the third segment ; lateral abdominal triangles often brownish-yellow ; 

 sometimes a reddish-brown shade in the middle of the wing ; for the 

 rest, like the male. 



Rab. — Manitou Park, Colorado (P. E. Uhler); Morino Valley, New 

 Mexico, July 1 (W. L. Carpenter); Denver, July 10 (A. S. Packard); 

 California (G. R. Crotch). Four males and eight females. 



This species is very variable in size; the four males and four females 

 from Manitou being only 9-10 mm long. My only specimen from Califor- 

 nia has the thoracic pile more reddish, that on the face more yellowish. 



Eristalis sp.— California (H. Edwards). Very like E. bastardi of the 

 Atlantic States, but different in the more metallescent surface of the 

 abdomen and the presence of two grayish thoracic stripes in the female, 

 abbreviated posteriorly. Some specimens from Vancouver Island seem 

 also to belong here. As the species seems to be variable, I do not attempt 

 to describe it with the insufficient material which I have on hand. 



Eristalis androcltjs Walker, List, etc., iii, 612. — The species 

 which, rightly or wrongly, Mr. Loew and myself have identified with 

 Mr. Walker's description, has a very wide distribution. It occurs in 

 Canada, in the White Mountains, in Western New York (Cayuga Lake) . 

 1 found several specimens near Ogden, Utah, August 2, 1876. Speci- 

 mens from Yukon River, Alaska, have the arista dark and the velvety 

 spots on the abdomen somewhat different. 



Helophilus latifrons Loew, Centur., iv, 73. — My Californian speci 

 mens agree with Dr. Loew's original specimens, and also with his de- 

 scription, except the words "hypopygium maris plerumque flavum". 

 In all my specimens, including Dr. Loew-s originals, the black ground- 

 color of the hypopygium is concealed under a thick yellowish-gray pol- 

 len, and is beset with yellow pile. 



H. latifrons (male) differs from H. similis (male) of the Atlantic States 

 in the greater breadth of the front (it is at least by one-half broader), the 



