April, 1910.] Four Genera of Horseflies. 151 



into collections. Front of normal width, sides very nearly 

 parallel although just slightly narrowed above; frontal callosity 

 large, as wide as the front and with an extension above; palpi 

 small, not distinctly compressed, much shorter than the pro- 

 boscis; face densely clothed with orange colored pollen; under 

 side of the head colored like the face and clothed with hair of the 

 same color; antennae situated on a very decided shining black 

 bulb-like prominence, first segment very large, spherical, shining 

 black and with some black hairs on the under side, second and 

 third segments yellowish-brown, the latter with a distinct prom- 

 inence very close to the base; sides of the thorax very densely 

 clothed with orange colored hair; legs black, front tibia enlarged 

 and curved, distinctly larger than its femur, middle tibia plainly 

 larger than its femur, hind tibia and femur of nearly the same 

 size; wing black except the tip of the second submarginal cell 

 which is hyaline, the outer limit of the black extends almost 

 straight backwards from the tip of the anterior branch of the 

 third vein. 



Snowiellus. Type species S. atratus from Arizona. Length 

 about 14 millimeters, body black, nearly opaque, form robust. 

 The genus was proposed by myself in 1904 and described after 

 having studied two specimens, the only ones I have seen. Front 

 wide, narrowed above; frontal callosity wide, as wide as the 

 front and with a connected spot above; palpi rather long but 

 somewhat slender, decidedly shorter than the proboscis; anten- 

 nae situated on a shining black elevation, first segment black and 

 clothed below with black hair, produced downward but not wid- 

 ened or produced upward so that from above these organs appear 

 perfectly normal, second and third segments opaque brown, the 

 latter with a distinct prominence very close to the base; face 

 mostly shining black; underside of the head clothed with black 

 hair; sides of the thorax black and clothed with black hair; legs 

 black, anterior tibia slightly enlarged, middle tibia less enlarged, 

 hind tibia only very slightly larger than its femur; wing black 

 with the exception of a hyaline area which curves around the 

 apex, occupying the apexes of the first and second submarginal 

 cells so that the outer limit of the black is marked by a curved 

 line from the apex of the second vein to the apex of the posterior 

 branch of the third vein. 



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