# Water in a bag keeps flies away?? **URL:** \ **Category:** Factual Questions\ **Created:** [June 15, 2003, 6:02pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056 "2003-06-15T18:02:58Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [June 15, 2003, 6:02pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/1 "2003-06-15T18:02:58Z")
I saw a bag of water hanging outside a friend’s window, and when asked why, she replied it was to keep the flies away. When I asked her how it worked, she had no idea, just saying it was an old wives tale. The bag is completely sealed, and just hangs from the roof swinging in the breeze. So what are it’s magical properties? ---
**Author:** ![raisinbread](https://avatars.discourse-cdn.com/v4/letter/r/8491ac/32.png) [@raisinbread](https://boards.straightdope.com/u/raisinbread)\ **Post date:** [June 15, 2003, 6:05pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/2 "2003-06-15T18:05:48Z")
The sunlight passing through the bag causes the illusion of movement and keeps the flies at bay. ---
**Author:** ![Number](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/number/32/242_2.png) [@Number](https://boards.straightdope.com/u/Number)\ **Post date:** [June 15, 2003, 6:10pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/3 "2003-06-15T18:10:33Z")
There was a [staff report](http://www.straightdope.com/mailbag/mwaterbags.html) on the subject. > [@](#): > > Apparently the water bags do drive houseflies away. Not mosquitoes, not no-see-ums, not spiders, not roaches, not yellowjacket wasps, just _houseflies_. Evidently, houseflies, being highly edible and defenseless, are nervous types, and don’t like to sit still when they see something moving nearby, because it could be a predator. The water bag acts a bit like a lens–try it some time–in which the movements of people in the area are reflected. Even if the fly is too far from the action to see it directly, it can see a shifting of light and dark in the water bag, which it interprets as nearby movement, and it will fly away from the bag. The reason it doesn’t work on any other insects is that the other insects listed don’t have eyesight worth a plugged nickel. ---
**Author:** ![FairyDust](https://avatars.discourse-cdn.com/v4/letter/f/ccd318/32.png) [@FairyDust](https://boards.straightdope.com/u/FairyDust)\ **Post date:** [June 15, 2003, 6:36pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/4 "2003-06-15T18:36:22Z")
> [@](#): > > \*Originally posted by liirogue \* > \*\*I saw a bag of water hanging outside a friend’s window, and when asked why, she replied it was to keep the flies away. When I asked her how it worked, she had no idea, just saying it was an old wives tale. The bag is completely sealed, and just hangs from the roof swinging in the breeze. So what are it’s magical properties? \*\* Did your friend say whether or not it has successfully kept away the flies? I’m going to try this method. We have a problem with flies hanging around our front porch. I’ve tried keeping potted basil plants out there, but that never worked, even though someone told me flies don’t like basil. ---
**Author:** ![raisinbread](https://avatars.discourse-cdn.com/v4/letter/r/8491ac/32.png) [@raisinbread](https://boards.straightdope.com/u/raisinbread)\ **Post date:** [June 15, 2003, 7:01pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/5 "2003-06-15T19:01:53Z")
Actually basil oil keeps flies away, not the basil plants. [Cite](http://www.ashburys.com/oil/eo_basil.htm). ---
**Author:** ![bouv](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@bouv](https://boards.straightdope.com/u/bouv)\ **Post date:** [June 15, 2003, 7:45pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/6 "2003-06-15T19:45:58Z")
Well, I read that to keep mosquitos away during a barbequr, place a large chunk of dry ice in a far away corner where no one will go. Mosquitos are attracted to CO[sub]2[/sub], and will all flock to the dry ice, and not you. Plus, some may try ot land on it and freezt themselves dead in the process. ---
**Author:** ![FairyDust](https://avatars.discourse-cdn.com/v4/letter/f/ccd318/32.png) [@FairyDust](https://boards.straightdope.com/u/FairyDust)\ **Post date:** [June 16, 2003, 1:05am UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/7 "2003-06-16T01:05:45Z")
Okay, I have prepared and hung five baggies of water from the railing of my front porch. I will check later and all this week to see if the flies are still a problem out there. Five bags might be overkill, but I am tired of seeing flies out there. ---
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [June 16, 2003, 1:30am UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/8 "2003-06-16T01:30:56Z")
Oooh **Fairy** , please do report back on what happens! ---
**Author:** ![FairyDust](https://avatars.discourse-cdn.com/v4/letter/f/ccd318/32.png) [@FairyDust](https://boards.straightdope.com/u/FairyDust)\ **Post date:** [June 16, 2003, 1:47am UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/9 "2003-06-16T01:47:39Z")
It may be too soon to tell, but just now I stepped out to see. I saw only two flies. Usually there are way more than that. I’ll check again tomorrow. It might also help if I hang some water-filled baggies from higher up. Currently the five baggies are waist-level hanging from the porch railing. This side of the house gets the late afternoon and evening sun. That’s when I’ll notice any real difference, such as now. ---
**Author:** ![j.c](https://avatars.discourse-cdn.com/v4/letter/j/73ab20/32.png) [@j.c](https://boards.straightdope.com/u/j.c)\ **Post date:** [June 17, 2003, 4:49am UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/10 "2003-06-17T04:49:34Z")
Has anyone else heard the dry ice trick for skeeters? I’d like to try that one… Of course, with my luck, someone’s kid will climb up to where ever I put it, and burn their little fingers, and there will be accusations and unpleasantness all around. ---
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [June 17, 2003, 7:24pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/11 "2003-06-17T19:24:51Z")
How did it go **Fairy**? I’ve never heard of it before, **j.c.** , but I’m going to give it a shot the next time we do something outside ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [June 17, 2003, 7:45pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/12 "2003-06-17T19:45:50Z")
Yep it works but you do not need to use bags. We have been doing this for years on our front porch. It makes eating outside very easy… Here’s what we do. Have you ever seen those glass spheres for sale, sometimes they are colored, sometimes they are clear? Buy a few clear ones. They look like [this](http://www.seashellcity.com/homedecor/images/BCH-2064.jpeg) and [this](http://www.floators.com/homedecorating/images/glassfloats.JPEG) . I live near the ocean so they are all over the touristy places down here. Anyway we cut a small hole in them with my dremmel and added some water. We see nary a fly all summer 🙂 Oh I learned it when I was in Arizona, they have them all over the place in outdoor restaurants. ---
**Author:** ![FairyDust](https://avatars.discourse-cdn.com/v4/letter/f/ccd318/32.png) [@FairyDust](https://boards.straightdope.com/u/FairyDust)\ **Post date:** [June 17, 2003, 10:19pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/13 "2003-06-17T22:19:52Z")
> [@](#): > > \*Originally posted by liirogue \* > \*\*How did it go **Fairy**? > > I’ve never heard of it before, **j.c.** , but I’m going to give it a shot the next time we do something outside \*\* So far it seems to only work when the sun it up and shining on those baggies. But later when that wasn’t the case, I could see a whole bunch of flies buzzing around my porch. ---
**Author:** ![FairyDust](https://avatars.discourse-cdn.com/v4/letter/f/ccd318/32.png) [@FairyDust](https://boards.straightdope.com/u/FairyDust)\ **Post date:** [June 17, 2003, 10:22pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/14 "2003-06-17T22:22:15Z")
:smack: I meant when the sun **is** up! Darn. Should have previewed. ---
**Author:** ![nebco9](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@nebco9](https://boards.straightdope.com/u/nebco9)\ **Post date:** [June 17, 2003, 10:31pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/15 "2003-06-17T22:31:23Z")
Do you have a light you can shine on the bags after the sun goes down ? It might work. ---
**Author:** ![nebco9](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@nebco9](https://boards.straightdope.com/u/nebco9)\ **Post date:** [June 17, 2003, 10:38pm UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/16 "2003-06-17T22:38:54Z")
OOPS! or maybe a light at night would attract other unwanted insects. Oh well… ---
**Author:** ![I\_can\_t\_believe\_that\_s\_butter](https://avatars.discourse-cdn.com/v4/letter/i/8edcca/32.png) [@I\_can\_t\_believe\_that\_s\_butter](https://boards.straightdope.com/u/I_can_t_believe_that_s_butter)\ **Post date:** [June 20, 2003, 4:19am UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/17 "2003-06-20T04:19:42Z")
> [@](#): > > Here’s what we do. Have you ever seen those glass spheres for sale, sometimes they are colored, sometimes they are clear? Buy a few clear ones. They look like this and this . I live near the ocean so they are all over the touristy places down here. Are these fishing floats you’re referring to? If so, I thought I’d add: Be sure to not drill any you may have found and look old, for instance; these are sometimes collectible, depending on size, and are thus worth varying amounts of money. ---
**Author:** ![Cardinal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cardinal/32/4000_2.png) [@Cardinal](https://boards.straightdope.com/u/Cardinal)\ **Post date:** [June 20, 2003, 7:30am UTC](https://boards.straightdope.com/t/water-in-a-bag-keeps-flies-away/182056/18 "2003-06-20T07:30:05Z")
You could buy one of those jar tops that traps flies when they smell the sweet liquid you put in the jar, and they can’t get back out. That would certainly reduce the number of flies in the immediate vicinity. [http://www.doyourownpestcontrol.com/traps.htm#fly](http://www.doyourownpestcontrol.com/traps.htm#fly)