Did you ever see a fly wipe his feet before he came into the house?
No, indeed; and he goes anywhere he pleases, over the bread and into
the cream. Yet he was born in dirt and bred in dirt, and he lives in
dirty places all the time he is not crawling over your clean things
and spoiling them.
Flies are hatched from eggs; and these eggs can hatch only in piles of
dirt, such as heaps of manure, or places where garbage and scraps from
the house are dumped or thrown. We call the common fly the "domestic"
or "house" fly, because he lives only in the neighborhood of houses
and barnyards where heaps of manure and piles of dirt are allowed to
gather.
When the fly first hatches from the egg, it is a little white,
wriggling worm called a _maggot_, like those that some of you may have
seen in decaying meat or fish or cheese. The maggots must have
decaying substances to eat and live upon while they are growing, and
this is why the eggs are laid in manure heaps and garbage piles.
[Illustration: A MAGGOT HATCHING FROM THE EGG
(Greatly magnified.)]
It takes the maggot about five days to grow to its full size, and then
it turns into a _chrysalis_. That is, it is shut up in a kind of case
that it has spun for itself, like the cocoon of the silkworm or the
caterpillar. In about five days more it breaks out of this cocoon and
appears as a fly with wings.
So, you see, the eggs must stay in that manure heap about two weeks if
they are to hatch. If, within that time, the manure is carted away and
thrown out somewhere where it will dry, the little unhatched flies
will be killed, or prevented from hatching. All we have to do, then,
to be entirely rid of flies about our houses is to see that the heaps
of manure and all piles of cans and garbage are taken away at least
once a week.
[Illustration: FLY MAGGOTS ON OLD NEWSPAPER