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 
letter 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. 
