Mrs. Fly has more than a hundred eggs to lay at once. It is quite plain she could not take care of so many babies. She must let them all look out for themselves.
Still Mrs. Fly shows much sense as to where she puts her eggs. She finds a place where they will be likely to live and get food and grow.
If the place is too wet the baby flies would drown when they leave the egg. If the place is too dry, they would wither up and die. Then, too, they must have soft food.
The fly does not lay her eggs on a stone or a piece of wood. She lays them in some kind of food.
The fly can live all summer if it has a fair chance. Cold kills flies. A frosty day will kill them. Some few flies, like a few of the wasps, hide, and live over winter in a torpid state, and in the spring they come out to rear new swarms.
Birds, spiders, wasps, cats, dogs, and some other animals eat flies. These creatures kill flies by millions. People kill flies with poison and fly-traps. If so many were not killed, we should be overrun with them.
In the South is a plant with a leaf like a jug. On the seam of this leaf hang drops of honey. Its juice can make the flies drunk.[14]
Flies like this juice. But as soon as they get it they turn dizzy and act just like drunken men. They fall into the jug-like space of the leaf and soon die. One of these plants will kill many flies in one day.
Many of our best birds live on flies, and if our birds were all dead we should have much greater trouble with the flies.
In the autumn you will see flies sitting about as if they feel dull and ill. If you look carefully you will see that the back part of the body is white. It seems to be covered with meal or mould.