160 ERNEST A. BACK. 



equal in length to the first two taken together, oval, dark brown, a 

 trifle shorter than the long slender black style. Thorax black, anterior 

 two- thirds of dorsum bare, highly polished; posterior third, lateral mar- 

 gins, pleurae and coxas, white pruinose; bristles of thorax, white. Ab- 

 domen polished black, posterior margin of segments 2—6 yellowish, and 

 white pruinose; fine pile of abdomen white. Legs deep testaceous, front 

 and middle tibias with a dark line down the sides; hind femora grad- 

 ually incrassate on the distal half with dark brown subapical testaceous 

 ring; the brown coloring of the incrassate portion extends as a dark 

 line along the anterior side of the whitish basal half. Hind tibiae dark 

 brown with a wide pale yellowish band on the proximal half; the 

 tarsal segments more or less pale straw with darker apices, the hind 

 tarsi, however, wholly brown. Wings pure hyaline, the second and 

 third posterior cells subequal, the fourth with a long peduncle. Em- 

 podia present, claws black. 



Type. — Collection of Prof. C. W. Johnson, Curator of the 

 Boston Society of Natural History. Two female and one 

 male co-types. 



Habitat.— Philadelphia, Pa., July 14, 1891 ; Folsom, Dela- 

 ware Co., Pa., July 23, 1893. 



This species is easily recognized from other Leptogasters 

 by its polished black mesonotum. 



Leptogaster badius (PI. VI, fig. 1). 



Leptogaster badius Loew, Cent., II, 6; 1862. 



cf 9- — Length 12- 15 mm. — Dorsum reddish-brown, polished, usually 

 with two rounded, more or less prominent polished black spots, one on 

 each side, behind the transverse suture; hind femora yellowish-brown 

 with a subapical brown ring. 



Brown, polished; antennae yellow, the third segment linear, tapering 

 gradually, not less than twice the first two segments taken together, 

 style black. Face white pruinose, pile of mystax white, occiput 

 grayish pruinose with pale bristles; palpi and proboscis testaceous. 

 Dorsum reddish-brown, highly polished, with two rounded polished 

 black spots (sometimes missing), one on each side behind the trans- 

 verse suture; dorsum behind these spots and on the lateral margins, 

 and the pleurae, coxas and scutellum thinly grayish-white pruinose. 

 Halteres pale. Abdomen obscurely brown, subfuscous, the median 

 bands of the several segments more or less obsolete; the anterior and 

 posterior margins of each segment are lighter, giving in fresh specimens 

 the appearance of a definite ring or band, and in some lights show a 

 thin white bloom. Bristles of the thorax brown; pile of pleurae and 

 abdomen, white. Legs polished yellowish-brown, the hind femora 

 gradually incrassate and bear a subapical brown band or ring; the 



