264 ERNEST A. BACK. 



(^ 9 — Length 10-13 mm. — Black, antennae of same color; bases of 

 all the tibiae and tarsal segments broadly yellow; mystax wholly 

 golden in the male, in the female edged with black; segments 2-5 of 

 abdomen with white pruinose spots; wings hyaline, toward posterior 

 margin and apex grayish. 



Black; face on the sides silvery, front brownish pruinose. Mystax 

 covering gibbosity; in the male very dense, wholly light golden except 

 on the oral margins, where it is black; in the female much thinner, in 

 the center golden, on the outside black. Antennas black; pile on 

 segments 1 and 2, on the front and occiput black. Beard white. 

 Thoracic dorsum yellowish-brown pruinose; the median geminate 

 stripe and the dilated lateral ones unequally black and polished. 

 When viewed from above there appear to be two rounded spots on 

 each side of the geminate stripe; one just above and behind the 

 humeri, the other before the transverse suture. The humeri, a broad 

 stripe extending from them over the base of the wings to the scutellum, 

 and the scutellum, aside from its base, polished black. Dorsum and 

 scutellum black pilose. Pleurae yellowish-gray pruinose with a bare 

 polished spot in the center, the mesopleura with fine black pile, the 

 sternopleura with pile; the trichostical pile whitish. Halteres whitish. 

 Abdomen wholly black, polished, white pilose; that of the male toward 

 the apex above and the hypopygium with black pile; the posterior 

 lateral margins of the segments 2-5 white pruinose. Legs black, 

 polished, the basal half or third of the tibiae and all the tarsal seg- 

 ments, except distally, yellowish; pile of the femora white except at 

 the tip, where, together with the bristles of the femora and the entire 

 clothing of the tibiae and tarsi, it is black. The front tarsi in the male 

 are more slender than those of the female; the last four segments on 

 their inner sides with pure white cilia. Wings hyaline, toward the 

 posterior margin and toward the apex grayish; veins black, at very 

 base, yellowish; the transverse veins slightly margined with fuscous. 



Type. — British Museum. There are at the M. C. Z. one 

 male and one female in Loew's collection; one bearing the 

 label " ? Falto Wlk." in Loew's handwriting. There are also 

 four specimens in Osten Sacken's collection. 



Habitat. — Nova Scotia (type, Wlk.), Quebec (Wulp), Mon- 

 treal Isl. (June 10, Chagnon), Canada; Franconia and White 

 Mts., N. H.; Mass. (June 1, 6 and 25), Axton, N. Y. (M. and 

 H.); N. J. (Smith Cat.); Fla. (C. W. Johnson); 111. (Osten 

 Sacken) . 



A fairly common species found in nearly all insect collections. 



