Fruit Fly Trap

In the summer I always seem to have trouble with fruit flies. Most of my fruit I can hide away in the fridge or a cold cellar but certain fruits cannot be chilled without being ruined. I have created a very simple trap to catch fruit flies.
I get a small jar or glass and put about a tablespoon of apple cider vinegar in it. Then i put plastic wrap over the top making sure it is secure around the edges. Poke a small hold in the plastic wrap for the flies to get in and voila! It works great, better than anything else I have tried before.