50 AMERICAN BLACK FLIES OR BUFFALO GNATS. 



degrees of intensity on the other segments. Legs black; in some 

 specimens brownish. Wings clear, thick veins yellowish or brown- 

 ish. Halteres yelloAv. 



Frons narrow, at vertex not occupying one-fourth the width of 

 head, slightly more than one-half as wide at lower angle as at upper 

 angle of eyes, surface hairs pale, weak, and regularly disposed; face 

 distinctly wider than frons at upper angles, one-fourth longer than 

 wide, hairs as on frons; proboscis very short, in none of the speci- 

 mens projecting more than length of face; palpi black-haired. 

 Scutum with very short, hairlike, regular, but not closely placed, 

 white pilosity, which is longer on posterior fourth; pleural tuft 

 yellowish white; scutellum with pale hairs. Abdominal basal scale 

 gray, the fringe pale yellowish white, all segments with distinct 

 close-lying pile or hairs, which are white in color and much longer 

 at apex and on sides. Legs with close-lying, white, hairlike pilosity 

 and longer, dorsal, pale hairs; hind tarsi with apex of basal joint 

 produced on posterior surface, second joint with basal scale and 

 constriction; claws bifid, as in Plate II, figure 16 (Prosimulium 

 pleurale). Hairs on basal portion of wing veins yellowish. 



Length, 2-3 mm. 



Kedescribed from type specimens, Friersons Mill, La., May, 1888, 

 and December, 1889, and a number of other specimens from Na- 

 pinka, Manitoba, June 20, 1907 (F. Knab), and Abbeville, Xinety 

 Six, and Greenwood, S. C, April, 1912 (Jennings and King). I 

 have also before me a series of specimens (14) taken in a house at 

 Knoxville, Tenn., by E. C. Cotton, which may be the form described 

 by Townsend as S. occidentale} Johannsen considered Townsend's 

 species as a small variety of meridlonale^ the early stages of the 

 former being unknown. The Canadian specimens in this series are 

 much larger (3-4 mm.) than those from Tennessee (1.5-2 mm.) or 

 South Carolina (2.5-3 mm.), but size alone is not a reliable criterion, 

 and structurally the insects appear to me to be identical. It is pos- 

 sible that the early stages may prove different in these forms, but 

 none of the characters given for their separation by Townsend appears 

 to be of specific value in the imagines. 



There are some specimens in the collection from Congaree, S. C, 

 April 9, 1912 (Jennings and King), which have the thoracic stripes 

 practically absent, but I do not feel justified in separating them as a 

 distinct species, as in other respects they agree with ineridionale.- 



Male. — Velvety, opaque black. Antenna? slightly yellowish on 

 basal two joints and base of third. Scutum with two anterior mar- 

 ginal pollinose spots of a Avhitish color, lateral and posterior 

 margins similarly pollinose; when w'orn slightly the stripes, so dis- 

 tinct on scutum of female, may be indistinctly traced; prescutuni 



1 Psyche, 1891, p. 107. 2 See Addenda, p. 63. 



