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October, the greatest activity being in the months of August and
September, this being greatly influenced by heat, the higher the
temperature the more rapid the development. Their chief breeding
place is stable manure, but they will breed equally well in any
collections of manure, or excrement, or any collections of waste
animal or vegetable substances, provided there is a certain amount
of moisture present, and the temperature is favourable.
The fly is an extremely prolific insect, a single female being
able to lay from 120 to 150 eggs at one time, which it usually
deposits in dark crevices, and this may be repeated five or six
times during its short life.
The metamorphosis of the fly. It must here be explained
that in the development of the fly from the egg, the insect goes
through certain changes of form and habit which are known as a
metamorphosis. The egg is first hatched and a maggot is produced,
which is called in technical language a larva. This hatching of the
egg takes place in warm weather in from eight to twenty-four hours
after the eggs are laid. The larva, which prefers dark moist places,
continues in this state about five days, during which time it moults
or casts its skin twice. At the end of this time, it is full grown,
having reached the size of ½-inch. At the end of the larval stage it
seeks a dry place, and encases itself with a dark reddish-brown
covering, which is called a puparium, in which condition it remains
at rest a few days, gradually undergoing the change from the pupa
to the developed fly. This period is known as the pupal stage.
If the temperature is high, the perfect fly emerges from its
sac between the 3rd and 4th day after pupation, by pushing off the
anterior end or the pupal case. Flies become sexually mature in
from 10 to 14 days after emergence from the pupal state, and four
days after mating, they are able to deposit eggs.