I have no idea, I just know they disappear once the sun goes down.
Sleep?
According to sites I’ve just had a look at, they rest near their food sources for larval reproduction areas, more than five feet from the ground.
Sorry, that should read “or” instead of “for”. :o
Welcome to the SDMB! 
And, for a first poster, yours is a really great question!
Unless they’re in your bedroom, in which case they buzz around your head all night.
In the dark? Either those flies wear little infra-red goggles, and like to par-tay all night long, or … you’re a food source.
When I’m camping, some of them roost on the inside walls of the tent, usually on the upper half.
The ceiling.
If you sleep with your mouth open they will go in your mouth and walk around looking for food.
I agree with Dr. Rieux. I see them on my ceiling at night. Take a look yourself.
Yep, all the flies go to handy’s ceiling.
Florida.
Now that you mention it, it only seems to happen when I’ve soiled myself. :eek:
Do they fly upside down to get to the ceiling, or go up like a helicopter, & then suddenly flip over? A serious question. (After all, scientists JUST, a month ago ,discovered that elephants don’t run.) They do a Groucho shuffle, so to speak, w/one foot on the ground at all times. But you all knew that.
Yep, they hang out on the ceiling. They fly close, then grab and flip up. I think there is a thread about it.
Peace,
mangeorge
Check this site.
Thanks. That line about 47 feet deep of flies reminded me: if all birds suddenly died, in one day the earth would be 6 feet deep with insects & I guess 8 legged bugs too. Wow, moral-be nice to birds.
<shrug> Search me! 
Early Out isn’t a food source, he’s a larval reproduction area…