I accidentally left the rind of a melon on the counter over night. We must have had 100 fruit flies on it the next morning. I tried to carry it outside with all the flies, but they just scatter. So I made this fly trap and my son and I watched and counted the carnage…
Used, clean food tub
Pour ½ inch or more cider vinegar in bottom of the container
Cover with plastic wrap
Secure plastic wrap with rubber band
Poke a few holes in the center of the plastic wrap
Set on counter and leave alone
The flies like the cider smell. They can get into the trap but not out. They eventually tire and drown. Clean out as needed by emptying washing and repeating. You can reuse the plastic wrap.