hatching, but apparently friction is 
not required. 
Larva—Newly hatched larvae 
burrow through the lips to the in- 
side of the lips just in front of the 
teeth. Here they remain for 6 weeks 
or more. 
Larvae then pass to various parts 
of the stomach, and attach them- 
selves to the lining. The greatest 
number attach near the stomach 
exit. 
Mature larvae release their at- 
tachment in the stomach, pass to the 
rectum, and attach again. They re- 
main here 2 or 3 days, then release 
their attachment and drop to the 
ground. The total period for larval 
development is similar to that for 
the other two species (10 to 11 
months). 
DAMAGE 
Horse bot flies damage animals 
indirectly and directly. 
Animals under attack may inflict 
damage on themselves or on anyone 
trying to handle them. Fright and 
irritation caused by egg-laying 
adults or newly hatched bots may 
result in animals going out of 
control. 
Direct damage is produced by lar- 
vae feeding on the tissues of the 
animal. 
Indirect Damage 
By flies—Animals fear the flies 
and are annoyed by them. The com- 
mon bot fly is the least annoying 
of the three species, probably be- 
cause it does not fly toward the 
animal’s head as do the throat and 
nose bot flies. 
On warm, sunny days, when bot 
flies are most. numerous, horses and 
mules on pasture fight the flies from 
morning until late afternoon. They 
walk about trying to get rid of the 
flies, constantly bobbing their heads 
as they walk. If this fails to prevent 
attack, they run. They may gather 
in the shade on high ground when 
the wind blows, or they may enter 
barns or other shelters. Colts which 
are heavily attacked may lie down 
near the older animals. 
While the horses are fighting the 
flies, they are unable to graze; after 
days of bot fly attack, they may lose 
weight and suffer from lack of 
proper nourishment. 
-Men who go near horses being: at- 
tacked by flies may be injured se- 
verely. Horses attacked in harness 
or when saddled often become un- 
controllable. Runaways commonly 
result. 
By larvae—Newly hatched bots 
produce a severe irritation as they 
burrow into the animal’s tongue, 
gums, or lips. The irritation and 
itching caused by the young nose 
bots is particularly severe. 
To relieve the irritation, animals 
may stand at watering troughs, dip 
their lips into water, and rub their 
lips violently against the wall of the 
tank. They may injure themselves 
by rubbing their lips and noses on 
the ground, fences, stones, or other 
objects. 
Direct Damage 
The bots attach themselves with 
spiny mouth hooks to the lining of 
the animal’s stomach or small intes- 
tine. These attachments cause in- 
5 
