OSTEN SACKEN ON WESTERN DIPTERA. 327 



recognized by him as 8. lapponicus. Four male specimens from Califor- 

 nia (Lagunitas Creek, Marin County, April 15; the Geysers, Sonoma 

 County, May 5-7 ; Yosemite Valley, Juue 5) do not differ in any essen- 

 tial character from the former. They are a little smaller, and the ab- 

 dominal lunate spots are a little broader ; the thorax is more greenish 

 than bluish. I have specimens from the Atlantic States, however, 

 which even in these particulars agree with my Californians. A speci- 

 men from British Columbia is larger, and resembles in all respects some 

 specimens from Maine and New York State. In Europe, the same dif- 

 ferences occur, and there seems to exist a good deal of uncertainty about 

 8. arcuatus and lapponicus, which differ only in the degree of curvature 

 of the third vein. My Californian specimens have this curvature 

 strongly marked, but among my eastern specimens there are some 

 where it is very weak. 



The reference to 8. affinis Say, in my paper (1. c, 149), must be 

 struck out (see ante, in 8. pyrastri). 



4. Syrphus americanus (Syrphus americanus Wiedemann, Osten 

 Sackeu, 1. c, 145). — I provisionally refer to this species a dozen of male 

 specimens taken in Marin and Sonoma Counties, California, in April and 

 May, and in Yosemite Valley in June. They are larger than the ordinary 

 specimeus from the Atlantic States, and measure from 9,5 mm to ll mm . 

 The first yellow cross-band is more broadly interrupted ; the two other 

 cross bands are very variable in breadth, sometimes narrower than their 

 black intervals, emarginate posteriorly. I have no females, and will re- 

 mark here that they have entirely yellow femora, and that the first 

 abdominal cross-band is, in most cases, not interrupted (compare 1. c, 

 p. 146); and, unless these characters are also to be found in the females 

 from California, their specific distinctness is no longer doubtful. 



A specimen from Oregon (H. Edwards) is smaller, and has the yellow 

 abdominal spots of the first pair laterally prolonged, so as to reach the 

 anterior corner of the segment (iustead of being entirely cut off from 

 the edge of the abdomen by a black margin). I am not sure about the 

 specific ideutity of this specimen. 



For a detailed description of 8. americanus, see my paper on Syrphus. 



5. Syrphus opinator n. sp. — Male. — Eyes glabrous; face, includ- 

 ing the cheeks, altogether yellow or reddish-yellow; no brown stripe 

 on the facial tubercle; antennae brown, reddish on the under side: 

 front above the antennae yellow, the angle between the eyes greenish, 

 black, yellowish pruinose beset, with black hair; small brown marks 

 above the root of the antennae. Thorax metallic-bluish-green, densely 

 beset with yellow pile ; the broad, geminate, grayish stripe in the mid- 

 dle is subobsolete. Scutellum yellowish- metallic-opalescent, beset with 

 black pile. Abdomen black, opaque on the anterior, subopaque on the 

 posterior part of the segments ; the two yellow spots on the second seg- 

 ment are prolonged anteriorly, so as to reach the lateral margin of the 

 segment at its anterior corner ; the two other cross-bands are rather 



