Fruit flies will follow the scent of the fruit down into the opening at the bottom of the cone, but once inside, they cannot find their way back out. After a couple of hours, you will probably find some fruit flies in your trap. This is where the humane part comes in: Take your trap outside, remove the tape and remove the paper cone to release the fruit flies.
Don't let your trap go unchecked for longer than overnight. You don't want to keep them trapped for too long, and if they stay in there for more than a day, the eggs will start to hatch.
Chances are, you didn't catch all of the flies in the first couple of hours, so you'll have to re-set the trap. To re-set the trap, remove the bait, replace it with a new piece of fruit, then tape the paper cone back into place. If you continue to use the same piece of bait, the eggs on it will hatch and you will end up breeding fruit flies inside your trap.
- If flies are not attracted to your trap, make sure there are no other attractants (food, garbage, dirty dishes, etc.) in the area. You can also try using a different kind of fruit as bait.
- If fruit flies are moving freely into and out of your trap, the hole in the bottom of the cone might be too large. Release any flies who are in your trap, then make the paper cone with a smaller hole in the tip. You want the hole to be barely larger than a fruit fly. Another problem may be that the paper cone is wrinkled and doesn't fit snugly into the opening of the the jar, all the way around. Make a new cone, and be careful not to wrinkle the paper.