46 AMERICAN BLACK FLIES OR BUFFALO GNATS. 



pollinose disk ; on each side of this central stripe there is a bhick stripe 

 which is slightly dilated anteriorly, does not extend either to anterior 

 or posterior margin, and becomes diffuse brownish on margins; 

 A'iewed from behind the two small, subtriangular spots are bright 

 silvery; the whole disk, except on the aforementioned black stripes, 

 white pollinose. Scutellum slightly white dusted ; postscutum silvery. 

 Abdomen with the segment below basal scale and sides of 5 and 6 

 more or less broadly silvered. Legs black ; tibia? white on dorsal sur- 

 face; bases of all tibiae yellow, the hind pair very noticeably yellow 

 on basal half; base of first joint of mid tarsus, all except apex of 

 first joint of hind tarsus, and base of second of the latter yellow. 



The jDilosity of the scutum is hairlike, pale yellowisli, longer pos- 

 teriorly; there are no black hairs present either on the disk or on the 

 scutellum. Basal abdominal fringe brown. Legs rather slender; 

 fore tarsus slender, the apical hairs not noticeable. 



I have not seen the larva of this species, but it is described by 

 Johannsen as having the teeth on the labium more nearly of an 

 equal size than in venustum; and the ventral surface of same with 

 seven seta? in each lateral row. The pupa has the respiratory organs 

 with eight branches (PI. VI, fig. 5). The cocoon is similar to that of 

 renvstum. 



Plscicidium was originally described from Mumford, N. Y., by 

 Riley, and was at one time considered to be, in the larval stage, 

 responsible for the death of young trout. This has been proved 

 to be a mistake. Two specimens of the original series only, marked 

 type, are in the collection. There are also several specimens in 

 the collection from Pine River, Lake Superior, September 7, 1896 

 (Hubbard) ; Kukak Bay, Alaska (T. Kincaid) ; and Lake View, 

 Miss., April 10, 1886. 



Coquillett considered this species as synonymous Avith venustum 

 Say, and Johannsen, though possessing larva? and pup?e, was unable 

 to separate it from Say's species in the perfect state. There is not 

 the slightest doubt that it is a distinct species, possessing char- 

 acters in all the stages which easily separate it from venustum. 



I have drawn up the description of the male from a specimen of 

 venustoides Hart, which is, I am convinced, synonymous with plscici- 

 dium. The specimens in the collection of the Illinois State Labora- 

 tory of Natural History are from Algonquin, 111., May, July, August, 

 and October (Nason). 



This is in all probability the species recorded as being such a 

 persistent biter in the Lake Superior district. 



Simulium tarsale Williston. 



The following is a copy of Williston 's original description : 



9. Abdomen black, tbe proximal segments opaque, the distal four segments 

 sbiuing. Length 2 mm. 



