Chlordane? Just kidding. You can make a redneck fruit fly trap out of an old jar. Take the lid from the jar and drill a hole in it, not too big, 3/16 or 1/4 inch should work. put a piece of very ripe fruit in it and put the lid with the hole back on the jar. The fruit flies are attracted to the fruit in the jar, and once they get in the hole in the lid, they cant figure how to get back out.
good idea! Prevention also helps: they will have already laid their eggs on most fruit coming into your house. So refrigerate all your fruit, to keep the eggs from ever hatching, and eat your bananas quickly (they don't refrigerate). Seal your breads up tightly, or again, put in the fridge. Don't leave any half-drunken glasses of soda around, keep things dry... when I lived at a co-op that was infested, the fruit flies even lived on the wet mop! We left our back door open, which didn't help; they could always come back in.
My younger days kicked in when I saw that topic title. A joke my old man told me: The short version is about nuns, green moldy cherries and fruit flies...
Old guy in Georgia once told me.....the way to get them all in one place and out of your face is to cut a hole in the seat of your pants. HE said it.
I've used a fruit fly trap I bought at the local hardware store which worked well. I've also put ripe fruit in a bowl sealed with plastic wrap, punch a few small holes into the wrap. The fruit flies are drawn into the bowl and rarely find their way out. Also check your kitchen drain, fruit flies like to lay their eggs in decomposing organic matter, a little bath of bleach down the drain helps things. Good luck, I hope your rid of them soon!