58 DIPTEEA OP NORTH AMERICA. [PART II. 



few indistinct minute black hairs ; middle coxae upon the greater 

 part of their outside grayish. Hind femora before the tip with a 

 bristle. Fore tarsi blackened from the middle of the third joint ; 

 middle and hind tarsi iufuscated from the tip of the first joint, 

 and towards their end gradually colored with black. Tegul^e 

 with black cilia. Wings tinged with gray, towards the fore mar- 

 gin more yellowish-brown, towards the basis narrower than in the 

 related species ; the fourth longitudinal vein not so much broken 

 as in the two previous species, the lower angle of the fracture 

 generally without stump, yet sometimes with a very short one. 



Male. Lamellae of the hypopygium of moderate size and of an 

 elongated ovate form, on the upper and apical ^nargin bordered 

 with black ; the latter one very much jagged and fringed with 

 black bristles. Hind femora not ciliated. Hind tibias not thick- 

 ened, hairy upon their entire hind side. Fore tarsi somewhat 

 longer than the tibia? ; two first joints stalk-lite, the first hardly 

 one and a quarter the length of the second ; the three last joints 

 taken together hardly longer than half the second joint, but very 

 little flattened, tinged with black beyond the middle of the third 

 joint ; the third joint upon its upper edge densely fringed with 

 longer, the fourth with somewhat shorter, black hairs. Wings of 

 a remarkable length, unusually narrow near the basis ; still their 

 rounded anal angle projecting almost in the shape of a lobe ; the 

 costa near the tip of the first longitudinal vein 'with a but slight 

 swelling. 



Hob. Middle States; Washington, D. C. (abundant in June; 

 Osten-Sacken) ; Chicago (id.). / 



Observation. I am in possession of a 9 which was communi- 

 cated to me as that of the present species, but which I consider 

 as that of D. scapularis. As D. longipennis sometimes occurs 

 without distinct fracture on the fourth longitudinal vein, so it 

 happens, on the contrary, that in some specimens of D. scapularis 

 the fourth longitudinal vein is somewhat broken ; they are how- 

 ever easily distinguished from D. longipennis by the pale color- 

 ing of their humeral callosities. The latter differs besides from 

 the females of all related species by its wings, which are somewhat 

 narrowed at the basis. 



