# A Baggie 3/4 Full Of Water And A Penny Keeps Flies Away? **URL:** \ **Category:** Factual Questions\ **Created:** [April 21, 2012, 7:16pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527 "2012-04-21T19:16:15Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 21, 2012, 7:16pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/1 "2012-04-21T19:16:15Z")
**D** has 2 of these pinned to the carport/house walls and it works. Why? Thanks Q ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 21, 2012, 7:24pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/2 "2012-04-21T19:24:52Z")
[The master’s staff speaks.](http://www.straightdope.com/columns/read/1956/whats-the-purpose-of-bags-of-water-hanging-in-restaurants) However, Doug gives no cites (horrors!) and I hae me douts. ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 21, 2012, 7:31pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/3 "2012-04-21T19:31:18Z")
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 ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 21, 2012, 7:56pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/4 "2012-04-21T19:56:10Z")
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. ---
**Author:** ![PapSett](https://avatars.discourse-cdn.com/v4/letter/p/ecc23a/32.png) [@PapSett](https://boards.straightdope.com/u/PapSett)\ **Post date:** [April 21, 2012, 10:08pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/5 "2012-04-21T22:08:48Z")
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… ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 21, 2012, 10:14pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/6 "2012-04-21T22:14:09Z")
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 ---
**Author:** ![Emtar\_KronJonDerSohn](https://avatars.discourse-cdn.com/v4/letter/e/58956e/32.png) [@Emtar\_KronJonDerSohn](https://boards.straightdope.com/u/Emtar_KronJonDerSohn)\ **Post date:** [April 21, 2012, 10:46pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/7 "2012-04-21T22:46:40Z")
I only ever see this in kitchens at Chinese restaurants. They don’t seem to bother the flies at all. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 21, 2012, 11:23pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/8 "2012-04-21T23:23:02Z")
> [@PapSett](#): > > 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… How do you know it “worked great”? No flies? By that logic, the deer dung in my yard keeps the elephants away. ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 21, 2012, 11:31pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/9 "2012-04-21T23:31:50Z")
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 ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 21, 2012, 11:37pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/10 "2012-04-21T23:37:42Z")
[Here’s a study under controlled conditions](http://www.ncmvca.org/Conference/2007_Meeting/Water_Bags_Optical_Fly_Repellent.pdf), 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](http://articles.orlandosentinel.com/2006-08-25/news/WATERBAGS25_1_water-bags-plastic-bags-flies) > [@](#): > > North Carolina State University researcher spent 13 weeks looking at the effects of water bags on flies at an egg-packing plant. Mike Stringham, also a veterinary entomologist, meticulously counted droppings left by flies on white “spot cards.” > > The results were conclusive: The water bags attracted more flies. > > “In the control room versus bags, the bags were consistently higher every time,” he said. 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. > [@Quasimodem](#): > > 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. Self-delusion could be one. No, I’m not being snarky. We human beans are very good at fooling ourselves. Check out [confirmation bias](http://www.skepdic.com/confirmbias.html) sometime. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [April 21, 2012, 11:44pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/11 "2012-04-21T23:44:08Z")
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. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 21, 2012, 11:49pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/12 "2012-04-21T23:49:53Z")
[Mythbusters tackled this in 2010](http://mythbustersresults.com/bug-special) > [@](#): > > Bags of water hung from the ceiling can repel flies. > > BUSTED > > This myth is based in the theory that refracted light in water confused flies’ compound eyes. > > The Build Team made a rig consisting of three chambers separated by trap doors. The first chamber would hold the flies, the second would hold some rotten meat, and the third would hold both rotten meat and a bag of water. They then released over 5,000 flies from the first chamber and waited to see how many flies would go into each of the other two. After the chambers were sealed off, they let all the flies die and collected the corpses to weigh for comparison. The chambers with and without the water contained 35 and 20 grams of flies, respectively, busting the myth. ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 21, 2012, 11:55pm UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/13 "2012-04-21T23:55:41Z")
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 ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 22, 2012, 12:26am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/14 "2012-04-22T00:26:22Z")
**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 ---
**Author:** ![PapSett](https://avatars.discourse-cdn.com/v4/letter/p/ecc23a/32.png) [@PapSett](https://boards.straightdope.com/u/PapSett)\ **Post date:** [April 22, 2012, 1:39am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/15 "2012-04-22T01:39:13Z")
> [@Musicat](#): > > How do you know it “worked great”? No flies? By that logic, the deer dung in my yard keeps the elephants away. 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. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 22, 2012, 2:49am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/16 "2012-04-22T02:49:07Z")
> [@PapSett](#): > > Quite frankly, I don’t care if anyone else thinks it works or not. If it works for me, that’s all that matters. That’s pretty much the sum total of efficacy proof for homeopathy, too. > [@](#): > > It keeps the elephants away pretty damned well too. Haven’t seen a single elephant since I started using it. Tolja. ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [April 22, 2012, 3:19am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/17 "2012-04-22T03:19:15Z")
No answer for \* me\*, then? Q ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 22, 2012, 3:45am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/18 "2012-04-22T03:45:36Z")
> [@Quasimodem](#): > > No answer for \* me\*, then? 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? ---
**Author:** ![Lanzy](https://avatars.discourse-cdn.com/v4/letter/l/74df32/32.png) [@Lanzy](https://boards.straightdope.com/u/Lanzy)\ **Post date:** [April 22, 2012, 4:02am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/19 "2012-04-22T04:02:59Z")
and Fans kill people in Korea ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 22, 2012, 5:03am UTC](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527/20 "2012-04-22T05:03:26Z")
> [@Quasimodem](#): > > **D** … > > So what about it, friends? We gonna shit or get off the pot?🙂 > > Quasi Did you mean “post”? [Next page](https://boards.straightdope.com/t/a-baggie-3-4-full-of-water-and-a-penny-keeps-flies-away/619527.md?page=2)