18 PARASITOLOGY. 
propagate. Houses should be screened. Sleeping 
zooms may be smoked with pyrethrum. The py- 
rethrum should be molded into cones and dried. 
These cones, when lighted, will smoulder for a long 
time, and give off a pungent odor which does not 
kill the mosquitoes, but stupefies them, rendering 
them harmless. 
SrmuLium PecuaruM (Pecus—cattle, simulo—to simulate.) 
Synonynt.—Buffalo gnat. 
History.—Found in the South, along the Mississ- 
ippiriver and its tributaries. Their destructive effect 
upon animals dates back as far as 1850. 
Description.—A small black fly; abdomen broad 
and thick; thorax short, thick and provided with a 
hump from which it gets its common name, resem- 
bling the hump of a buffalo. The antennae are com- 
posed of eleven segments. Its wings are wide and 
short, and its three pair of legs are thick and short. 
Lite Cycle.—The adult flies are found from April 
until after June. They lay from 5,000 to 10,000 eggs 
in a compact mass on some object directly over the 
water’s edge. Upon hatching, the larva falls into 
the water. The larva is composed of twelve joints. 
It fastens itself to rocks and other objects in the 
river bed, often loosening its hold and floating in the 
current till another favorable place is found. The 
larvais carnivorous. The pupal stage is passedina 
tough brown cocoon with the upper part open. This 
cocoon is fastened to sticks and other objects in the 
water. 
Animals Intested.—They attack the animals, as 
horses and cattle, in swarms. By means of their 
