Where do flies go in winter?

SMALL children tend to go through a phase where they ask incessant questions. At times this can be irritating for adults but occasionally they throw out a really good question. Like the little girl who asked me the other day: “where do flies go in the winter?”.

I thought about this. The word ‘fly’ can apply to a lot of insects with wings but she was obviously referring to the common house fly. They are one of the most widely distributed animals in the world, found practically everywhere there are higher forms of life. But it’s believed they evolved in the middle east and spread with humans as our species colonised the globe. This sub-tropical origin means they are not equipped to cope with an Irish winter.

The life-cycle of the house fly is quite typical for an insect. Eggs are laid in decaying organic matter. This is most commonly of vegetable origin, unlike the eggs of blue bottles which are normally laid in decaying animal matter. The eggs hatch into larvae, which are commonly called maggots. The maggots go through three instars, or moults, getting bigger each time. They then pupate inside a hard, reddish brown shell before hatching into adult flies with wings.