1875.] 145 [Osten Sacken. 



femora in some specimens are black at the extreme base only; the 

 hind femora are altogether yellow, thus widely differing from those 

 of the male). 



Length, d, ?, about 8 mm. 



Three male and six female specimens, all from Massachusetts. 



The Museum of Comparative Zoology, in Cambridge, Mass., pos- 

 sesses a pair (d, ?) of European specimens obtained from Dr. 

 Schiner, exactly similar to the American specimens; they also show 

 all the sexual differences, as explained above. Zetterstedt's descrip- 

 tion (Dipt. Scand., viii, p. 313G, 13-14, ?) agrees very well with 

 my female specimens. Schiner is certainly wrong in uniting abbre- 

 viate, Zett. ? with excisa Zett. d ; (Loew makes the same criticism in 

 the Jahrb. d. K. K. Gel. Ges. in Krakau, Vol. 41, p. 16; only excisa 

 should be read there, instead of emarginata). 



Observation. In my Report on the Diptera of Colorado Territorv 

 (U. S. Geol. and Geogr. Survey, etc., by F. V. Hayden, for 1873, 

 p. 564), I mention S. corollce as occurring there. I was mistaken in 

 this determination; the specimen is more like S. abbreviates, although 

 I would not, without further proof, identify it even with this species. 



5. S. americanus. 



Syrphus americanus Wiedemann, Auss. Zw., n, p. 129, 22. 



Female. Face yellow, often brownish, with a brown stripe in the 

 middle, which begins at the oral margin, but does not reach the 

 antennae; the latter brown, reddish on the underside of the third 

 joint. Cheeks blackish, but separated from the mouth by a narrow 

 yellow border, which, on the underside of the mouth, completely cuts 

 off the connection between the black color on both sides. Front 

 brownish bronze color, powdered with yellow on each side; the 

 lower part of the front is more or less yellow, but immediately above 

 each antenna there is a brownish spot, which sometimes coalesces 

 with the bronze color of the upper front; vertex bronze color. Eyes 

 bare. The first abdominal crossband is not interrupted, but coarctate 

 in the middle; its ends do not touch the margin of the abdomen, but 

 are separated from it by a narrow black border; (sometimes a brown- 

 ish mark in the middle of this band gives it the appearance of beino- 

 subinterrupted). The second crossband is nearly as broad as the 

 black crossband between it and the next yellow band; it is usually 

 perfectly straight; (in some specimens the hind margin is gently sin- 

 uate) ; its ends do not touch the lateral margin of the abdomen ; they 

 are cut obliquely, forming a sharp angle anteriorly, and a rounded 



PROCEEDINGS B. S. N. H. — VOL. XVIII. 10 NOVEMBER, 1875. 



