OSTEN SACKEN ON WESTERN DIPTERA. 329 



of the male hypopygium. In the female, the fifth abdominal segment 

 is about half as long as the preceding, while in Syrphus proper the 

 relation between the corresponding segments is as 1 to about 3 or 4. 

 The scutellum in both sexes is unusually raised, exposing the metano- 

 tum more than in Syrphus; in the female, it has a distinct yellow bor- 

 der, which is not the case in the known American species Of Syrphus. 



The sixth abdominal segment in the male is as long as the two pre- 

 ceding segments taken together, but narrower ; it is convex, almost 

 tubular, when seen from above, and unsymmetrical, its end pointing 

 slightly to the right. The seventh segment on the under side of the 

 sixth bears the opening of the anus. Beyond the anus, on the under 

 side of the body, there are two long, linear, subparallel appendages, 

 arcuate, bidenticulate at the end ; these appendages are bent under the 

 body when in repose, and are imbedded in a horny groove on the under 

 side of the sixth segment, which encroaches on the fifth ; when in mo- 

 tion, these appendages come out of the groove like a blade of a pen-knife, 

 at an angle to the axis of the abdomen ; in length, they are nearly equal 

 to the whole sixth segment. 

 The name has reference to the structure of the hypopygium. 

 Eupeodes voluoris n. sp. — Male. — Eyes bare. Face whitish-yellow, 



• with black cheeks and a brown stripe over the facial tubercle ; front 

 whitish-yellow, with some black pile; antenna? dark brown; vertex 

 black. Thorax dark metallic-green, sometimes slightly bluish, with 



i very pale yellowish pile; scutellum yellowish, more or less metal - 



I lescent, with pale yellow pile; abdomen black, opaque; the first seg- 

 ment, the lateral and posterior margins of all the segments, shining; 

 the fifth altogether shining; on the second segment two yellow oblong 

 spots, well separated from the lateral margin ; on each of the two fol- 

 lowing segments, a pair of larger, oblong, yellow spots ; those on seg- 

 ment 3 very slightly lunate; the posterior margins of the fourth and 

 fifth segments with narrow yellow margins. The sixth segment is black, 



| shining, sparsely beset with whitish pile ; its shape has been described 



| in the generic character. Legs reddish ; base of femora black ; hind 

 femora black, except the tip; hind tarsi more or less brown on the upper 



i side. Wings hyaline; stigma yellowish-brown ; anterior costal cell hya- 



] line, the posterior tinged with yellowish. 



Female. — Front and vertex black ; across the black a faint subinter- 



\ rupted arcuate stripe of pollen, leaving a triangular glabrous black 



■ space below ; lower part of the front yellow, except a dark brown cres- 

 cent-shaped spot above the root of the antenna? ; a narrow yellow space 



I between this spot and the black above. Scutellum distinctly yellow 

 along the edge ; the black at the root of the femora is a little less ex- 

 tensive here. Length very variable, from 10 mm down to 7 mm . 



I Hab. — California, Nevada, Utah, Colorado, common. I found it com- 

 monly in Los Angeles in February; in Marin County in April; in Yo- 



j Semite in June ; in Utah in August. I also have specimens from Den- 



