30 AMEEICAN BLACK FLIES OR BUFFALO GNATS. 



Simulium trivittatum, new species. 



Female. — Yellow, opaque. Frons and face thickl}^ white-dusted; 

 antennae browned from third joint to apex; palpi brown. Scutum 

 with three broad, parallel-sided, chocolate colored stripes, the central 

 one not reaching to scutellum and the lateral pair not reaching to 

 anterior margin ; posterior margin of scutellum darkened in center ; 

 space between the stripes white-dusted ; pleura? brown on center and 

 slightly white-dusted; scutellum yellow; postscutum brown, subshin- 

 ing. Abdomen with basal scale yellow ; segments yellow, with opaque 

 black-brown marks which leave very little of the yellow ground color 

 visible, apical four segments not so much darkened as basal four. 

 Legs yellow, black as follows: Apices of tibiae and all except base 

 of tarsi of fore pair; apices of first and second and apical three joints 

 of mid and hind tarsi ; apices of femora and apices of tibiae of hind 

 pair. Wings clear, thick veins yellow. Halteres yellow. 



Frons divergent-sided, two-thirds as wide at above antennae as at 

 upper angle of eyes, surface hairs w^eak, yellow ; face longer than 

 frons and one-third longer than broad, surface hairs as on frons; 

 postocular cilia pale. Scutum with very short hairlike yellow pilos- 

 ity; pleural tuft yellow; scutellum with yellow pilosity and longer 

 upright brownish hairs. Basal fringe on abdomen yellow; all seg- 

 ments with short, scattered, yellow hairs. Legs with pale pilosity 

 and scattered longer dorsal hairs on tarsal joints; fore tarsi slightly 

 thickened ; tarsal claws simple. Wing venation normal. 



Length, 2 mm, 



Type.—Q^i. No. 15408, U. S. National Museum. 



Locality. — Tampico, Mexico (E. A. Schwarz). 



Readily distinguishable from any described species, except dis- 

 tinctum, by the brown vittate scutum. 



Simulium distinctum. Malloch. 



This species was described subsequent to the completion of the 

 present jDaper, but the description appeared some time ago in the Pro- 

 ceedings of the Entomological Society of Washington, 1913, page 133. 

 It is unnecessary to reproduce the description here. S. trivittatum 

 closely resembles distinctum., though I believe they are distinct. 



Locality. — Devils River, Texas. 



A specimen from Tamaulipas, Mexico, is with some doubt referred 

 here also. 



Simulium ochraceum Walker. 



Female. — Yellow, opaque. Face and frons brownish yellow, thickly 

 white-dusted ; antenniie yellow, from fourth joint to apex browned ; 

 palpi black-brown. Scutum with two white poUinose vittae, and 



