These Fruit Fly Traps are AWESOME. They solved my kitchen fruit fly problem in under 24 hours. Even with a flat of tomatoes and two ripe cantaloupes on the counter, the fruit flies still went right for the trap. Best of all, they fell in and stayed in. I've made many homemade traps that attracted tons of flies, but allowed probably 85% to still escape again. Not so with this design. This is the fruit fly trap of DOOM.
The traps are empty, dry, little plastic containers, and you add liquid attractant to them--it comes in a separate dropper bottle in the kit. I suspect it's apple cider vinegar, but fairly pale and weak. Technically you can add whatever liquid you wanted into the trap, so I saw an opportunity for an experiment.
The first night I got these, I made two traps - one with the liquid attractant, and one with apple cider vinegar from my pantry. In this case, it was a fancy organic unfiltered variety from Whole Foods that had been in my pantry for at least three years. "Spectrum" brand.
Next morning: Trap with the manufacturer's attractant: 4 flies. Trap with apple cider vinegar: 19.
How long can you use them?
The design isn't exactly easy to rinse out. I guess the idea is that they last until the liquid is so full of flies that the trap ceases to be effective, and then you toss them and use another. But if you're willing to put a few minutes of messy work into it, it's possible to re-use them. Take a full trap, top it off with water, and shake it until most of the liquid (and flies) are out. Refill and repeat until all the flies are gone. Finally, shake as much water as you can out of it and then re-fill carefully with drops of fresh apple cider vinegar.
UPDATE: I've used these again and again for 2 years now.
Definitely get different apple cider vinegar though because it was MUCH more effective than the attractant liquid. I tried a couple of brands, and darker-colored apple cider seemed to work better than lighter. Throw out the attractant - it's uselessness is probably the reason for the 1-star reviews.
I also ran tests later with wine, balsamic vinegar, and fruit juice. Those baits worked a little bit, but didn't come close to how well apple cider vinegar performed. These work so well that I actually give them as gifts to chef friends.
You can get these Fruit Fly Traps from HERE.