324 ERNEST A. BACK 



dish-brown, and the stripes themselves are not black, but more brown- 

 ish; this coloration is most noticeable in greased specimens in which 

 the bloom has been affected. Pile of the thorax white, that on the 

 dorsum mostly black; all the bristles black, in a few specimens partly 

 white on the posterior callosities. The scutellar bristles, about three 

 on each side of the posterior margin. Abdomen black; the lateral 

 margins of all the segments and, sometimes, the extreme posterior 

 margins as well, are brownish; rather bare, covered with very short 

 black pile, on the sides with longer white pile; posterior angles of 

 segments 1-4 whitish or yellowish pruinose. Venter reddish-brown, 

 whitish pruinose, with white pile, longer toward the base, toward the 

 apex, black. Legs brown; apices of the femora, tibia? and of the tarsal 

 segments, largely black; pile mostly white, on the tips of the tibiae 

 and on the tarsi black; femora toward the apex with a few bristles, 

 mostly black; tibiae with many bristles, mostly whitish or yellowish, 

 some black; bristles of tarsi, black. Halteres pale yellow Wings 

 long, hyaline, costal cells and the apical half of the wing blackish; the 

 whole of the discal cell and the fourth and fifth posterior cells toward 

 the base, however, clear; veins black. 



$. — The male does not differ appreciably from the female except 

 in the secondary sexual characters of the legs. The front metatarsi 

 only are clothed above with dense appressed white pile; there is a 

 little white pile on the second segment also, but here it is not notice- 

 able. The middle femora on the outer half above with short black 

 hair in the middle of which is an oval bare area; the middle tibia? clothed 

 before with dense appressed white pile, and a trifle above the middle, 

 with a brush of black hair and bristles; all the other bristles of the 

 tibia?, except at very tips, white. The pile of the coxa?, metapleura? 

 and venter of abdomen is white and longer than in the female, and the 

 blackish cast to the wings is confined to a smaller area at the tip. 



Type. — M. C. Z. There are five female specimens in the 

 Loew collection; they are the type of gibbus. Dasypogon 

 macerinus is in the British Museum. 



Habitat. — Trenton Falls, N. J. (type, macerinus) ; (type, 

 gibbus), Ky. ; Lehigh Gap, Pa. (July 16, H. L. Viereck). 



This species is at once separated from lautus and phwnicurus 

 by the rather broad median velvety black stripe on the 

 thoracic dorsum, which is separated from the similarly colored 

 lateral stripes by narrow light pruinose lines which are always, 

 in good specimens, very distinct. Specimens become greasy 

 and then the velvety blackness of the stripes is lost. Osten 

 Sacken states (Western Diptera, page 310) that he had species 

 from California and Vancouver Island which were not unlike 



