Two of the four places that I stick fruit to attract natural fruit flies are in the "formerly" overflows of the aquarium. From here the flies can naturally migrate into the system and breed without predation. When they get a little to prolific I use an idea borrowed from others here to collect them. I use this to catch the fruit flies. Then I pour them into a cup and sprinkle with dust which makes them flightless. They usually are stunned enough when I open the dustbuster that they won't fly away and I can get them into a collection cup to be dusted without to many escapees. This would make a great way to massively culture fruit flies outside. I place a window screen over the overflow. This provides enough of a barrier to slow them down while they are trying to escape when I am vaccuming them up. The picture is from one day collecting-I got the same amount the day before from the same spot.
