x] Flies 155 
Horses should be watched for the eggs during the 
months they are likely to be present, ie. from J uly to 
October. The legs should be well brushed or washed 
with warm water in order to hatch out the eggs. The 
droppings of infected horses should also be watched for 
the bots. 
Sheep Nasal Fly (Oestrus ovis). 
This grey fly may be seen in early summer flying 
around sheep, especially in hot weather. The flies 
settle on their noses from time to time in order to lay 
their eggs or to deposit newly hatched larvae. The 
sheep often try to keep them off by rubbing their 
noses on the ground and may show uneasiness when 
the flies are near them. 
The maggots pass into the nasal cavities of the 
sheep where they live for about 10 months on the 
mucous discharge caused by their presence. Badly 
infested sheep have a mucous discharge running from 
their noses, and often sneeze violently. They also 
rub their noses on the ground. They may frequently 
shake their heads and hold them on one side. This 
state of affairs is known as false gid, and is due to the 
presence of the maggots in the nasal passages. It 
must not be confounded with true gid, which is caused 
by the cyst of a tapeworm. 
When fully grown the maggots come out of the 
nose or are forced out by the sneezing of the sheep. 
They make their way just below the surface of the 
ground and change into brown puparia. From these 
the flies come out in June and July. 
The condition of infected sheep is considerably 
reduced and in severe cases they may die. 
