D has 2 of these pinned to the carport/house walls and it works.
Why?
Thanks
Q
The master’s staff speaks. However, Doug gives no cites (horrors!) and I hae me douts.
Ah, okay, thanks Musicat. I can see the reasoning with the bag acting as a lens and picking up movements which scares the flies away, but the penny? My late sister in law did this, but she learned it from someone else and didn’t question it, so no one knows. We just put the penny in there. 
Q
I can see the reasoning with the lens, too, but the whole thing seems an awful lot like an urban legend, penny or no. Until I see some adequate double-blind tests, I will continue to be suspicious.
Honestly, I did it last year at my back door without a penny in it and it worked great! It’s about time to put another one out, in fact…
Yeah, that penny thing has me bamboozled. Maybe it was for luck, like we used to do in the 60’s with “Penny Loafers”?
God, I loved those things! De rigueur for high school!
Thanks
Q
I only ever see this in kitchens at Chinese restaurants. They don’t seem to bother the flies at all.
How do you know it “worked great”? No flies? By that logic, the deer dung in my yard keeps the elephants away.
It’s too bad there isn’t a cite for this. If it works fine for PapSett and I, there’s got to be a reason.
We have one of those green rolling “dumpsters” which get emptied by the garbage trucks every Tuesday, and none of us have ever seen flies around that thing, and it is under the carport till it gets moved…
Quasi
Here’s a study under controlled conditions, or at least vastly more controlled than anecdotes, that claims that the water-filled bags caused INCREASED fly activity nearby. Not increased number of flies, which appeared to not change.
http://articles.orlandosentinel.com/2006-08-25/news/WATERBAGS25_1_water-bags-plastic-bags-flies
The study is presented like a Power Point show, and gives several theories how it MIGHT work, IF it does.
However, the study was not done with sunlight, but artificial light. Should sunlight be a factor, this test would not be adequate to make a determination.
Self-delusion could be one. No, I’m not being snarky. We human beans are very good at fooling ourselves. Check out confirmation bias sometime.
For what it’s worth (which is basically nothing) it was a huge fad in my camping festival communities a few years ago, but I hardly see anyone doing it anymore. Which makes me think that even if it does work, it may not work well enough to justify the effort and ugliness for many people.
I haven’t tried it myself due to skepticism. And laziness.
Everyone: Please remember these Baggies are placed under the carport and away from direct sunlight. They were placed the same way at my s-i-l’s house, who also had a carport.
How about this, y’all? How about if I place a hamburger that’s being fixed right now and won’t be eaten, on the carport floor?
Would that work for everyone? 
Quasi
D and I just had a “mini argument” about this (we don’t yell or go to bed without a “love you”, so it really is just a disagreement).
Here’s what she said: “You told them those things are out there and are stopping the flies. Why in the hell do you need to prove it with a damn piece of hamburger meat??”
Here’s what I told her: My friends are some of the smartest people in the world and that means they sometimes need scientific proof of what is asserted, which is why they post cites of scientific studies proving a thing is right or wrong. This isn’t Facebook, Honey, and they aren’t just gonna take my word for it.
So what about it, friends? We gonna shit or get off the pot?
Quasi
Well, I say it works great because before I hung the bag of water, EVERY TIME I opened the back door, at lease 4 or 5 flies dashed inside. Every. Single. Time.
After I hung the bag of water, there were no more than 1 fly coming in with every 4th or 5th door opening. HUGE cut back on the flies.
Quite frankly, I don’t care if anyone else thinks it works or not. If it works for me, that’s all that matters.
It keeps the elephants away pretty damned well too. Haven’t seen a single elephant since I started using it.
That’s pretty much the sum total of efficacy proof for homeopathy, too.
Tolja.
No answer for * me*, then?
Q
Who are you expecting to reply? Me? Haven’t I given enough cites to show the question is still up in the air, but the chances of water bags repelling flies are slim?
The only positive replies we have heard are anecdotal, and the possibility of self-deception is great.
Just what do you think would be accomplished with a rotting hamburger on the floor?
and Fans kill people in Korea
Did you mean “post”?