Osten Sacken.] 142 [October 6' 



8. The metallic green thorax is somewhat more shining, less dull 

 than in S. torvus; in many specimens, however, this difference is 

 scarcely perceptible. The brown ring on the hind tibiae, sometimes 

 expanded so as to reach the tip, occurs in this species as often as in 

 S. torvus. 



I had about seventy males and ninety females for comparison, prin- 

 cipally from the White Mountains; (a large lot was collected there 

 by Mr. H. K. Morrison); also from West Point, Catskill, N. Y., 

 Manlius, Western New York, etc 



Some rare specimens occur with a distinct brown stripe in the 

 middle of the face; I found four such specimens, two males and two 

 females, among my lot. Mr. Malm mentions a variety of the Euro- 

 pean S. ribesii, with all the crossbands interrupted. I have two such 

 specimens from Fort Resolution, Mackenzie River, and from the 

 Yukon River (both collected by R. Kennicott). As these specimens 

 disagree in some minor characters also, I am not sure whether they 

 can be taken for 5. reel us. 



I may mention here that the sexual difference in the coloring of the 

 legs is not an exceptional character in this species; in S. nbbrevia- 

 tus, as will be shown below, the same differenee exists. 



Observation I. This is the representative of the European S. ri- 

 besii No European author mentions the difference in the color 

 of the hind femora of male and female as it exists in American speci- 

 mens; this silence would authorize the belief that such a difference 

 does not exist. 1 And yet, the few female specimens of S. ribesii 

 which the Museum of Comparative Zoology possesses, among them a 

 specimen labelled by Mr. Loew himself, all have yellow hind femora, 

 while in the males they are dark. The most common species are the 

 very ones which are often the least known and worst described, and 

 this may have been the case with S. ribesii. In comparing the state- 

 ments of different authors about this species and S. topiarius, a great 

 want of agreement, as well as of precision, becomes apparent. And 

 it may very well have occurred that the dark legged females of topi- 

 arius passed for females of ribesii, whenever the pubescence on their 

 eyes was sufficiently rubbed off to render the mistake possible. 



iZetterstedt, Dipt. Scand., n, is the only one who has a statement bearing .on 

 this point. He says about S. ribesii : " femoribus basi in J 1 latius, in $ angustis- 

 sime atris." But in the American specimens, as well as in the European speci- 

 mens whieh 1 have seen, the eoxie are black, but there is hardly any vestige -of 

 black at the base of the femora in the female. 



