This is not all Flys on my work bench windows all dead but in warm heat they come back alive.

My grandparents had a summer home upstate NY, we would go up in the winter and first thing you'd have to do is sweep up the flys, windrows of them, before you turned on the heat, any that you missed would soon be spinning in circles and then take off, folks there called them buckwheat flies....apparently the house wasn't that tight, lol

Pillbugs here thousands of them this summer.

I call the zombie flys.

We built a new cabin this year. Last weekend every window had dozens of flies flying around. You couldn't put a dent in them with a vacuum. This weekend, there are a couple here and there. It's like Cotton-eyed Joe... where did you come from, where did you go?!

We call them cluster flies.
I think they are an invasive species introduced to kill some other pest.

Fly’s are terrible here as well.

We call them cluster flies too. They do lots of spinning on their backs