42 AMERICAN BLACK FLIES OR BUFFALO GNATS. 



usual longer dorsal hairs weak; fore tarsi dilated, as broad as tibiae, 

 first and third joints with paired apical hairs; hind tarsi of similar 

 form to venustum Say; claws simple. Wing venation normal, sur- 

 face hairs and short bristles brownish yellow. Sometimes the pilosity 

 on scutum is brownish or almost black, but this is exceptional. 



Length,, 1-1.5 mm. 



Ty2J>e.— Cat No. 15412, U. S. National Museum. 



Male. — Similar in size and color to the female except that the 

 mesonotum is velvety opaque black; the scutum has two silvery or 

 pearlaceous stripes running from the margin of the prescutum back- 

 ward and inward to almost middle of disk ; the lateral and posterior 

 m.argins of scutum are distinctly silvery pollinose; the pilosity is 

 darker and longer, being more hairlike than in female. The abdomen 

 is not distinctly shining on apical segments, and the hairs are longer 

 and darker. The legs are similar in color to those of the female, 

 but the tibiae are only pale at extreme base; they are longer haired 

 and the claws are trifid (see PI. V, fig. 12). The eyes are of similar 

 formation to those of the males of venustum. 



Allotype. — Cat No. 15412, U. S. National Museum. 



There are reared specimens in the collection bearing the number 

 4425. These emerged from pupae sent to the Bureau of Entomology 

 in May, 1889, from Friersons Mill, La. 



An examination of the pupa discloses the fact that this is in all 

 probability the species described in the larval and pupal stages by 

 Johannsen in the paper already mentioned. I give a copy of the 

 characters mentioned by Johannsen for his variety a of venustum, 

 which he was unable to separate from the type except by size in the 

 imago. 



A number of specimens bred from larvae and pupae taken from Fall Creek, 

 Ithaca, New York, differs in the adult stage from venustum as described above 

 in being uniformly smaller (length 1.5 mm.) ; having the base of wing brownish 

 and not yellow, and in having the last four abdominal segments of the female 

 a shining black instead of brown. The larva differs as follows : in size averag- 

 ing less than two-thirds that of venustum, labrum [labium] with its toothed 

 edge wider in proportion to its size than in venustum, its teeth more nearly of 

 a size, the ventral setae three in each row, plus a very small one. The pupa 

 differs in having 10 respiratory filaments in each tuft, the hooks on segment 2 

 more distinct, and the tubercules on the anal segments apparently wanting. 



This species stood in the collection as S. venustum Say, and both 

 sexes are represented among the specimens reared from the pupae 

 from Friersons Mill. There are specimens in the collection from 

 Spring Hill, Fairfax County, Va. ; Chevy Chase, Md., July 4, 1907 ; 

 Cabin John, Md., May IG, 1909; Beltsville, Md., September 21, 1911; 

 and Washington, D. C, July 3, 1910 (F. Knab) ; Minnesota (Lug- 

 ger) ; Liman, Spartanburg, and Gramlin, S. C. ; and Flat Rock, 

 N. C. (Jennings and King) ; and Biscaj'ne Bay, Fla. (Mrs. A. T. 



