Where do flies go/what happened to flies in winter?

Factual Questions
1

This is something that has bothered me for many years and no matter how many people I ask (even C.A). No on has been able to answer me.
Every year when its colder and coming into winter all the flies disappear. I have NEVER seen a fly in winter. Now that its coming into summer they are all starting to rock up and annoy the hell out of me.
I find it hard to be leave that they hibernate since they generally live for only 20days.
And it doesn’t seem like they would all die out when winter comes because then how do we see them again in summer?

So with high hopes that the member of the SDMB are able to help me. Where do flies go/ what happened to flies in winter?

2

Either they lay eggs and die or overwinter in their larval or pupal forms.

There are breeds of flies that appear in the winter – cluster flies, for example, will migrate into buildings and appear even when it’s freezing outside.

3

Well here we don’t have any flies in winter (not to my knowledge, but i have never seen on or know anyone that has).

So flies will spend 3-5months in this state?