150 Flies [CH. XI 
hatched out in it. It has since been shown that the 
eggs are not laid on the backs where the warbles are 
found, but are laid on the hairs of the legs and sides 
of the cattle. They are very difficult to find as they 
are placed on the hairs close to the skin. The small 
larvae which hatch out from the eggs have been seen 
to bore into the skin when placed on it. The next 
stage of the larva is found in the wall of the gullet and 
from this it was for some time supposed that the eggs 
or maggots were licked into the mouth. How the larvae 
get from the egg into the gullet 1s not yet known. 
From the wall of the gullet it is thought that the 
larva bores its way through the tissues to the position 
in which we find it under the skin of the back. The 
eggs are laid during the summer, the actual date 
varying according to the climate. Flies have been 
seen as early as June and as late as the middle of 
September. 
The maggots live in the backs of the cattle until 
May or June. The lumps containing them have holes 
which ensure a sufficient supply of air. 
When fully grown the maggot is about 1 inch long 
and of a blackish-brown colour. It is segmented and 
wrinkled. It has no legs but possesses a number of 
very small hooks which are situated on transverse 
ridges. The anterior end has a pair of fork-like jaws 
and at the posterior end are a pair of dark brown 
spiracles which touch each other (see Fig. 47). 
They set up inflammation in the flesh and cause a 
quantity of pus to be formed, on which they feed. 
As we should expect from the presence of the spiracles 
at the tail end, they live head downwards. When fully 
grown the maggots make their way out of the lumps 
