How to 
Three species of horse bot flies are 
serious pests in this country. 
The common bot fly and the throat 
bot fly oceur throughout the United 
States. 
northwestern and midwestern States. 
The nose bot fly occurs in 
Bot flies can be controlled by treat- 
ing infested animals to destroy larvae 
and eggs. 
HOW BOT FLIES LIVE 
Bot flies have four life stages— 
adult, egg, larva (bot), and pupa. 
The life stages are described on pages 
4 and 5. 
The adults (flies) do not feed. 
Their sole purpose in life is to re- 
produce. They live from a few days 
to 3 weeks. 
In northern States, flies appear 
% 
M & A 4267 
Adult female bot fly. 
Control Them 
about the middle of June; they live 
until there is a heavy freeze. In 
southern States, they appear as early 
as March and may be seen until 
December. 
Eggs usually can be found on 
Egg 
laying continues as long as adults are 
horses as soon as flies are seen. 
present. Eggs of the common bot 
fly that can hatch may be found on 
the animals as late as December in 
northern States, and as late as Feb- 
ruary in southern States. 
During the larval stage, the bots 
develop inside the animal; they grow 
from minute size to about two-thirds 
inch in length. The exact nature of 
the food they take is not known, but 
they feed on body fluids. 
Mature bots may be found in the 
digestive tracts of horses and other 
equines at any time of the year, but 
they usually pass out of the animals 
by October. Practically all the bots 
found in animals during the early 
part of the winter are young. 
When fully developed bots pass 
out of the animal and reach the 
ground, they seek protection. They 
Usually they bur- 
row into the ground near the place 
crawl very little. 
where they were dropped. They 
burrow only deep enough to escape 
the direct rays of the sun. 
