MAT FLIES AND MIDGES OP NEW YORK 275 



are wanting, or replaced by others nearer the anterior pair. The 

 lateral fins of the seventh and eighth segments have four or five 

 pale, slender filaments; the caudal appendage is fringed with 

 slender hairs, and there are three stout setae at each angle of the 

 apex. 



Imago, female. (P1.30, fig.8) Grayish black. Length 2.5 to 

 3 mm. Wholly grayish or brownish black, including head with 

 all its parts, thorax and abdomen. Legs pale brown; fore legs 

 nearly wholly bare, middle and hind ones sparsely haired. Fore 

 metatarsus about 0.6 as long as its tibia. Wings slightly smoky 

 hyaline, anterior veins brown, posterior veins hyaline. Venation 

 as shown in figure. Halteres dull black. 



Male. Wholly black, very slightly shining. Thorax with a 

 suggestion of three black dorsal stripes; the other parts dull. 

 Abdomen with dark brown hairs. Antennal hairs, black. Legs, 

 dark brown, or almost black, fore tarsi nearly bare. Anal angle 

 of wing prominent ; anterior veins broAvn, wings slighty cinereous. 

 Genitalia black. Length 3.5 mm. In other respects like the 

 female. 



This species differs from s t e r c o r a r i u s in having smoky 

 wings in both sexes, abdomen of female darker, and in having an 

 aquatic larva. Ithaca N. Y. The following is a copy of Fitch's 

 description. 



Black; poisers obscure brown; wings pellucid-cinereous, their 

 anterior nervures blackish. Length about .15 inch to the tip of 

 the abdomen in the male — females one third shorter. 



This species is black throughout, and clothed with fine black 

 hairs. The thorax has three slightly elevated longitudinal ridges 

 immediately forward of the scutel. The wings, when the insect 

 is at rest, are held against the sides of the abdomen, often verti- 

 cally in the males, but more commonly in the females with their 

 inner margins in contact, thus forming a steep roof covering the 

 back. They are diaphanous, of a cinereous tinge, and feebly irri- 

 descent. Their inner margins toward their bases are slightly arcu- 

 ated. The suibmarginal or postcostal nervures — those which 

 bound the closed basillary cell, and which proceed from this cell 

 to the margin — are particularly obvious, being of a blackish color,' 

 excepting the nerve which proceeds from the inner angle of this 

 cell to the apex of the wing, which, with the nervures inside of it, 

 scarcely differ in color from the surface which they ramify. The 

 poisers are oibscure-brownish, truncated at their apices, the capitu- 

 lum being in the form of a reversed triangle. The abdomen in 

 the female is shorter than the wings, somewhat compressed, ap- 

 proaching to an ovate form when viewed laterally, with the venter 



