mane, the shoulders, the belly, the 
neck, and the flanks. Fly takes but 
a second to attach each egg. Several 
eggs may be fastened to the same 
hair; many may be attached to the 
mane and flanks. 
One female can lay 500 eggs. 
Egg.—Yellow. Ready to hatch 
in about 7 days. Eggs hatch any 
time (within 2 or 3 months). The 
animal licks or bites itself at the 
spot where eggs are attached; heat 
and moisture from the animal’s 
mouth stimulate hatching. 
Larva.—Newly hatched larvae 
are taken into animal’s mouth 
when it licks or bites itself. Larvae 
burrow into tongue. They continue 
to burrow for 3 to 4 weeks, then pass 
into the animal’s stomach, attach 
themselves, and remain until ma- 
ture. The total period for larval 
development is 10 to 11 months. 
Mature larvae pass out of animal 
with feces. 
Throat Bot Fly 
(Gasterophilus nasalis) 
Adult.—Smaller than common 
bot fly and more rapid in flight. 
Wings have no markings. 
Female poises in midair, usually 
near the animal’s forelegs, then 
darts at the animal to attach eggs 
on hair under the jaws; cements one 
to four eggs to a hair during each 
attack, flies away after each attack; 
returns in a few minutes. 
One female can lay 500 eggs. 
Egg—yYellowish. Hatches in 
about 6 days. Does not require mois- 
ture or friction for hatching. 
Larva.—Newly hatched larvae 
crawl into animal’s mouth. Usually 
4 
Pupa—Similar for all three 
species. The pupal stage begins 
1 to 4 days after the bots burrow 
into the ground. The outer skin 
of the larva hardens to form a 
protective coating—the pupal 
case—this case is brown or black. | 
The bot changes into a fiy within | 
the pupal case. At the end of the 
| pupal period, which ranges from | 
15 to 70 days, the fly emerges 
from the pupal case and mates. 
| Another life cycle begins. 
they lodge in the pockets between 
the molars. 
In 20 to 30 days larvae pass from 
the mouth into the stomach, then 
into the forward end of the small 
intestine, where they attach and re- 
main until mature. The total period 
for larval development is 10 to 11 
months. 
Mature larvae pass out of animal 
with feces. 
Nose Bot Fly 
(Gasterophilus haemorrhoidalis) 
Adult—Smallest of bot flies; 
most rapid in flight. Most hairs on 
body are dark. Wings have no 
markings. 
Female darts at the lips of the 
animal; deposits one egg at the base 
of the hair, then darts away. A few 
seconds later she strikes again. Eggs 
are deposited close to the skin, 
usually along the front of the upper 
and lower lips. 
One female can lay 160 eggs. 
Egg.—Black. Hatches in about 2 
days. Moisture is necessary for 
