I dont know about outside but inside the ole "apple cider vinegar" works like a charm for fruit flies. I put a little in a dish/bowl , add a drop of dish soap, cover with cling wrap and punch tiny holes for the flies to enter, they will go in but wont come back out. Place near where they are congregating even if its right on your worm bin . This does not work for gnats. Its also easy to tell which you have. Gnats are slow long legged fliers and fruit flies are fast fliers. It seems the FF are the ones attracted to the worm bins as they try to lay eggs in the food you put in thats why its important to cover with a nice layer of shredded paper each time.

I hope it's okay to resurrect an old thread, but I have a question re mesh screen and fruit flies ... From this page here, http://homeguides.sfgate.com/determine-mesh-size-window-screen-25184.html, we can calculate how tight a mesh screen is by cutting out a 1 square in piece of fiberglass or other mesh screen and counting how many holes there are in that square inch to figure out the "density" or frequency of the holes to determine the size. But what size will actually keep out fruit flies, anyone know? I don't actually know the size of mesh screen holes that will keep these pesky flies out. Does anyone? I've looked and looked on the net but haven't found a thing. I brought home a roll of figerglass mesh home from my local hardware store but took it back yesterday because it seemed the holes were big enough for the flies to get through. At any rate, didn't want to risk it so didn't open package as the mesh wasn't cheap. Before I go out and buy again, want to know best size to use. Thanks for any help re this! :D

Let me tell you my tale of woe which is still increasing my blood pressure even tonight. For the past 5 days, my house has been inundated with some type of small flies; maybe drain flies, but I have a coffee angle as well. This morning, I used the foot peddle on a plastic Rubbermaid trash receptacle in the kitchen........there must have been at least 25 in the garbage and many flew out all over my kitchen and dining room. I had noticed most seeming to come from the kitchen sink/drains, so I used the foaming disposal/drain cleaner at least twice, but that had no impact. I made coffee as usual this morning, using my Cuisinart 12-cup coffee maker, although I just make one cup and use paper filters and some organic ground coffee. I didn't really look "into" the coffee maker this morning, but I had just run vinegar and water through it the other day for the auto-clean cycle, which it really needed. Like some others in this thread have mentioned, I don't think that the standard cleaning touches every opening within the coffee maker where moisture may be allowed to linger. Later in the day, it appeared that many of these flies were around my coffee maker........to my horror, when I opened the lid on top, there must have been 15 or 20 inside the coffee maker. Even after I rinsed it out and attempted to dry it off, more flies were landing on it. It was like a horror film. I tried putting into two plastic grocery bags, since I didn't have a single bag big enough, and I shortly realized that there were flies getting into the bags like the coffee maker was a magnet. I then cleaned the coffee maker in the sink, and cleaned the canister as well and hand dried each and put the coffee maker into two other plastic bags and put it in my home office at the other end of my house. I put the canister in a separate bag and tied the top and did the same with the basket. (as I type this, there are flies landing on my hands and arms......Alfred Hitchcock can't be far away) I would guess that I have killed about 100 of these flies in the past 4 days and still am not entirely sure where they came from, but I have read that drain flies breed and hatch every 48 hours and I seem to just keep coming. If these things were in my coffee maker this morning, I must have ingested a lifetime's worth. I seem to have two sizes of these flies and the only way to kill any of them is when the land on the counter. When they are flying, it is extremely hard to kill them. I believe they are attracted to carbon dioxide, because they have flown into my eyes, nose and mouth. They sound like mosquitos when they fly near my ears. I may try the apple cider vinegar and dish soap idea before going to bed shortly, but I'm afraid that I wake up with even more tomorrow. I have read that you can add some sugar to this mixture as well. The dish soap is important. Since I could not eat lunch or dinner today because so many were landing on my food and plates, and I had to throw food away, this is really taking its toll. They are going into my kitchen cabinets and have tried to get into the microwave. I am putting many scraps that might have gone into the garbage into separate bags and tying them off. There is no open food or waste in my kitchen. I even sprayed flying bug spray into the garbage when I discovered the infestation there and it made no difference.....nothing kills these things........help !!! UPDATE: I used two suggestions found online that seem to help. One is to build a simple fly trap using apple cider vinegar and dish soap in a cup/container and put plastic wrap on top, secure with a rubber band and poke some small holes in the top with a toothpick. Flies get in; can't get out. Other thing is the suggestion to use a spray bottle and fill with water and dish soap. You can zap flies when they land somewhere and it makes it easier to kill them. Run water and disposal more frequently to make sure there is no "organic matter" that can attract more flies.

We put some diluted bleach down each of our drains after reading about that online. For some reason one bathroom also has a couple. No food in sight there so figured maybe they're in the drain lines? The company that I bought the electronic trap from emailed me and asked how it was going. When I told them it wasn't, they suggested putting a cotton ball with wine on it in the trap to help attract the flies. Haven't tried that but it's next on the list. I did notice they were attracted to an empty wine glass that hadn't been washed yet.