Several years ago we had a horrible gnat problem. They came in through the holes in our window screen, and I did not know how to get rid of them at the time without harmful pesticides. But if you have a problem with gnats, you can make a homemade gnat trap quite simply. All you need is a glass, some apple cider vinegar, and some paper.
You can make this trap by making a funnel out of your piece of paper, which is then placed in the opening of a glass that has apple cider vinegar in it. The apple cider vinegar lures the gnats in, but the funnel keeps them from getting out. Make sure your funnel hole is not too big, or the gnats will be able to get back out.
After you have made a funnel with your paper and have checked how far down it will sit in your glass, pour the apple cider vinegar in the glass so that it will be as close as possible to the bottom of the funnel (of course do this without the funnel in the glass). The gnats prefer glasses instead of plastic cups. These traps can be placed where you see gnats the most. Go here to see pictures of the trap.
Edited to add: I can't remember how well this worked for gnats, but it definitely worked great for fruit flies!
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