SIMULIUM. 31 



laterally beyond these stripes a jx'ar-shaped brown mark with the 

 narrow extremity toward the wing base, which stops short of the 

 prescutum and does not touch the white stripes; pleurae brownish; 

 scutellum yellow. Abdomen with the apical se^ients more or less 

 blackened and subshining. Legs yellow, blackened as follows: Mid 

 and hind coxae; fore tarsi except base; apex of first, apical half of 

 second, and entire apical three joints of mid tarsi; apices of femora, 

 apical half of tibife, apical half of first and second, and entire apical 

 three joints of tarsi on hind legs. Wings clear, thick veins yellow. 

 Halteres yellow. 



Frons divergent-sided, at above antennae about one-third as broad 

 as at vertex, bare in center, laterally and more broadly posteriorly 

 covered with golden pilosity and among the pile some longer, upright, 

 black hairs; face one-third longer than broad, uniformly but not 

 tliickly covered with short, yellow pilosity; antennal pilosity whitish; 

 palpi broAvn-haired ; postocular cilia mostly yellow, with a number 

 of longer, black hairs. Stripes on scutum as broad at anterior mar- 

 gin as the space between them, gradually diverging and somewhat 

 curved posteriorly, becoming narrower and ceasing at a little beyond 

 middle of disk ; extreme lateral margins of scutum whitish pollinose, 

 pilosity golden yellow, scale-like and regularly distributed ; no black 

 hairs on scutum; pleural tuft brown; postspiracular area brown- 

 haired posteriorly; scutellum with pale yellow pilosity and long, up- 

 right brown hairs. Abdominal basal fringe pale yellow, long; seg- 

 ments Avith scattered, short yellow pile and a few longer back hairs 

 intermixed with them. Leers with close-lving yellow pilositv and 

 scattered, longer, upright, dorsal brown hairs; fore tarsi with the 

 normal paired apical hairs on joints 1 and 3 ; claws as m Plate II, 

 figure 15. Diagrams of the thoracic elevations of this and the follow- 

 ing two species are shown in Plate V, figures 6-8. 



Length, 2 mm. 



Two females, Cordoba, Mexico (E. Knab). 



The records of the occurrence of this species in the United States 

 which I have had the opportunity of examining are erroneous and 

 refer to notatmn Adams. (See note under notatum^ p. 33.) 



Simulium bivittatum, new species. 



Female. — Ocherous, opaque. Frons and face thickly white-dusted, 

 antennae from apex of third joint to apex of eleventh browned, 

 palpi brown. Scutum with two broad, almost parallel-sided, white- 

 pollinose vittae: extreme lateral margins of scutum white-pollinose; 

 prescutum and scutum near to it pale yellow ; pleurie yellow, browned 

 on middle; scutellum ocherous; postscutum black. Abdomen yellow, 

 segments 2-G with a distinct black dorsal spot and brown lateral 



