where the gnats go at nights?

Answer 1

They are still out and about. If you have them in your house this works really well to get rid of them.
fill a coffee cup about 1/4 full of apple cider vinegar and place them close to where you see them and in a couple of days when you look inside the cups you will see they are filled with the dead flies.

Answer 2

To the gnat cave!!

Answer 3

hunting for flesh .my mosquito net and insect repellant stops them
and they are out in force in the evening and night
the hot sun tends to thin them out