XI] Flies 153 
amount of shade so that they can take protection 
from the fly. 
The best method of keeping down this pest is to 
examine cattle in the spring and to squeeze out the 
warbles between the thumbs and destroy them. This 
is a much more satisfactory method than putting some 
kind of grease or ointment on the animals’ backs in 
the spring in order to stop up the holes. No dressing 
has yet been found which will kill the maggots without 
injuring the skin. 
The practice of squeezing out the maggots if carried 
out systematically by farmers would considerably 
reduce the number of flies, because, as far as we know, 
the backs of cattle contain nearly all the warbles 
during the winter, and if these were destroyed few flies 
would remain to infect cattle the following year. Young 
stock are more frequently warbled than older ones. 
Horse Bot (Gastrophilus equi). 
Damage is sometimes caused by the maggots or 
bots of a fly known as Gastrophilus equi living in the 
stomach of horses. When present in large numbers 
the wall of the stomach may become ruptured with 
fatal results. In small numbers little damage is 
done. 
The brown and grey fly lays its eggs on the hairs of 
horses’ legs or in some position in which the horse can 
reach them with its tongue. They are fixed very 
tightly on the hairs so that the horse cannot lick them 
off. One fly is said to lay over 500 eggs. In about four 
or five days the larvae hatch out inside the eggs, where 
they remain until warmed by the licking of a horse’s 
tongue. They then come out of the egg and pass into 
