SIMULIUM. 25 



on the surface; prescutum with upright, rather strong, brownish 

 hairs; pleural tuft indistinct; scutellum with pale brown, upright 

 hairs on posterior margin; postscutum produced. Basal abdominal 

 scale yellowish-brown, fringe white, abdominal segments with scat- 

 tered pale hairs. Legs with weak pale hairs; no distinct apical tibial 

 sjDurs ; hind tarsi as in Prosimulium^ tarsal bristles very weak ; claws 

 short and stout, simple. AVings with long hail's on thick veins, vena- 

 tion as in Plate I, figure 4. 



Length, 1.25 mm. 



Type.— Cat. No. 15405, U. S. National Museum. 



One female, Bairs Ranch, Eedwood Creek, Humboldt County, Cal. 

 (H. S. Barber). 



Nothing is known of the early stages of this species. 



SIMULIUM Latreille. 

 TABLES OF MALES. 



As most of the species are known in the female sex only, it is not 

 possible to include all the species described from North America in 

 this table. 



1. Species with noticeable yellow marks on abdomen or thorax 2 



Species mostly black, only the legs and antennae with yellow markings. 3 



2. Small species, 1 mm., mostly yellow colored ; scutum indistinctly 



striped notatum, p. 33. 



Larger species, 1.5 to 2 mm., mostly black colored; scutum distinctly 

 striped distinctum, p. 30. 



3. Legs with basal joint of hind tarsus not bicolored 4 



Legs with basal joint of hind tarsus bicolored 5 



4. Pilosity of scutum whitish a 



Pilosity of scutum golden yellow, or brassy h 



a. Scutum unstriped ; dorsal excision and scale on second joint of 



hind tarsus indistinct mcridionale, p. 49. 



Scutum with black stripes as In female, the outer one on 

 each side curved ; second joint of hind tarsus with distinct 



scale johannseni, p. 65. 



h. Pilosity of scutum and abdomen brassy, scale-like bracteatutn, p. 38. 



Pilosity of scutum yellow, hairlike, especially hairlike on abdo- 

 men forbesi, p. 64. 



5. Small species (not more than 2 mm. in length) ; mid tarsus mostly 



yellow 6 



Larger species (at least 2 mm. in length) ; mid tarsus with at most 

 bases of first and second joints pale. 



6. Scutum almost entirely covered with pearlaceous pollinosity ; one dis- 



tinct, opaque black, central stripe present grisenm, p. 53. 



Scutum with two anterior pearlaceous, posteriorly incurved, elongate 

 spots, disk velvety black jenningsi, p. 42. 



7. Scutum with distinct stripes ' S 



Scutum with at most two posteriorly incurved spots on anterior margin. 30 



