To add to the last posters advice, place some saran wrap on top with a rubber band, or plastic baggie, poke some holes on top so they can fly in but they can't find their way out. I use wine instead of vinegar, the fruit in it seems to attract them more, and still put some dish soap too. you will have a nice little collection on your counter top, but it does do the trick. You have to do it for a few days to get any that have hatched recently. It is the season for flies but are usually gone by november. i battle them every year.