When pesky fruit flies are swarming, here’s an easy do-it-yourself trap. Place a funnel with a tiny opening or roll a sheet of paper with a small opening at the bottom, then place in a container with a piece of fruit at the bottom.  When the flies are all out of the room and into the jar, you can release them outdoors.  (When using rolled paper, you may need to tape the paper to the jar to the flies don’t escape.)

Source:  theidearoom.blogspot.com