254 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



Fore coxae 3^cllow, their anterior surface with small black hairs 

 and a few very delicate yellow ones along the outer edge. Middle 

 and hind coxae black with yellow tips. Femora and tibiae yellow. 

 Middle and hind femora each with one preapical bristle, the latter 

 ciliated with long yellow hairs on central portion of the lower inner 

 edge, the longest hairs being considerably longer than the width of 

 the femora. Middle tibiae with three bristles below, one pair near 

 apical third and one bristle near basal third, their basitarsi with one 

 large bristle above. Posterior tibiae distinctly thickened; the 

 glabrous stripe on upper surface reaching nearly their whole length, 

 inner surface with a broad glabrous space extending two-thirds their 

 length and not reaching base or tip. 



Fore tarsi (fig. 186a) about one and three-fourths times as long as 

 their tibiae; first three joints slender, yellow, second about two- 

 thirds as long as first, third three-fourths as long as second and a 

 little longer than fourth, as long or slightly shorter than fifth joint; 

 fourth and fifth joints much compressed and widened, fourth white 

 with a silvery luster on the sides, fringed above with minute black 

 hairs and usually with several on outer side; fifth joint black, a little 

 wider than fourth, somewhat oval, but straight below, two-thirds as 

 wide as long, a little longer than the fourth, fringed above with black 

 hairs. Middle tarsi one and a third times as long as their tibiae; 

 middle and hind tarsi infuscated from the tip of first, or base of 

 second joint, but only the last two joints black. Calypters, their 

 cilia, and the halteres yellow. 



Wings (fig. 186) grayish; costa moderately enlarged at tip of first 

 vein; last section of fourth vein bent near basal third; hind margin of 

 wing scarcely indented at tip of fifth vein ; anal angle rounded, but a 

 little prominent. 



Female. — Face wide, grayish white; fore tarsi plain; a little longer 

 than their tibiae, yellowish with only the last joint black; bristle on 

 middle basitarsi near its middle; costa without enlargement; hind 

 femora without cilia below. 



Described from many males and females. The collection of J. M. 

 Aldrich has males from Woods Hole, Massachusetts, taken September 

 25 (Hough), and from Lafayette Indiana, taken June 11-July 4. 

 C. W. Johnson has males from Niagara Falls, New York, June 24 ; 

 Mathias Point, Virginia, May 22 ; Popes Creek, Maryland, May 22 ; Fall 

 River, Massachusetts, June 17, and Manomet, Massachusetts, July 27. 

 I have taken it at Ridgeway, Ontario, June 18-July 15. 



jT^/pe.— Male, Cat. No. 23055, U.S.N.M., from Ridgeway, Ontario. 



