Inexpensive fly control?

[urbpan]

Thanks to macabre_grrl for pointing me to this post at hip_domestics. It's a post about an inexpensive house fly control method that is apparently widespread among restaurants with outdoor seating, farmers markets, and the like. But I had never heard of it.

The method is to fill a clear plastic bag with water and hang it up where you would like to keep flies from. This particular post included a detail which set my bs detector off like a klaxon. There is a shiny new penny in the bag with the water. Why? Because, according to the restauranteurs who hung the thing up, "flies have compound eyes and see the penny's reflection as a honeycomb beehive. Flies don't want to be near them and stay away from dining guests."

Nuh-uh. While it is true that flies have compound eyes, their nervous systems are able to gather the information from those eyes into images that help them navigate their environment, avoid predators, etc. If they saw a single penny as a beehive, they would also see a single predatory wasp as an overwhelming swarm! Every pile of dog doo would be a mile wide buffet! To belabor the point, I'll draw attention to the fact that we have two eyes, and we don't mistake every single thing for a double thing. (Despite what you might have learned in a Monty Python skit about mountain climbers.)

Back to the bag of water. Why should flies be repelled by it? According to the staff at The Straight Dope, the bag acts as a crude magnifier, "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."

Maybe. I don't totally buy it, but I haven't tested it. Fortunately, someone suggested it on the Mythbusters forum, so maybe those guys will try it out. Keep in mind that for this to work in the way that the Straight Dope guy said it does, that there have to be people around, their images dancing around in the plastic bag in a way that menaces them (in a way that the people themselves don't, for some reason.) Other message boards discussing this folk pest control method say that it works, but like most visual repellents (shiny balloons, fake owls) the effectiveness drops off once the pests acclimatize to the stimulus.

Wait, so what about the penny? According to one message board comment, the penny is there to prevent algae from growing in the water, which (according to the comment) would only work if it was a penny minted before 1982, back when they were still made of copper.

I suspect that the biggest benefit of folk remedies, whether they're for health, pest control, or attracting good spirits, is the fact that they make the person feel involved. "I did something to make it better: I put a penny in a bag of water, I rubbed the wart with a penny, and then I put the penny in my shoe." It's very human to want to feel like your actions are meaningful. And like most folk remedies, a bag of water at least won't make it worse.

Comments

[nmsunbear.livejournal.com]

One of my favorite restaurants, The Cowgirl in Santa Fe, uses the water-filled plastic bags. (I have not noticed pennies; I'll have to look closely next time.) Their patio doesn't seem to me to have fewer flies than I would expect. (New Mexico doesn't seem to have a lot of flies anyway.)

Have you heard about the supposed remedy for dogs peeing on your lawn of water-filled plastic milk jugs around the edge of the lawn? I've seen it a few times, can't imagine that it works.

[urbpan.livejournal.com]

I in fact encountered that "remedy" whyile researching the fly thing. If anything, that would give the dogs a target for their scent marking. I have seen posts designed to attract marking dogs, which would tend to concentrate their efforts in one place--which is a form of control.

I'll look into it and see what the deal is. Maybe the jugs are filled with ammonia or some other powerful unpleasant smell that makes the dogs move on.

[nmsunbear.livejournal.com]

If anything, that would give the dogs a target for their scent marking.

That's exactly what I thought! Do post if you find any more info on it.

[urbpan.livejournal.com]

As suspected, it's bunk:

http://www.straightdope.com/classics/a3_070.html

http://www.snopes.com/critters/wild/lawn.asp

(The snopes article says "undetermined," but lists the same specious reasons why it's supposed to work.)

[sin-agua.livejournal.com]

I'd never heard of this until living in southern Arizona. We've seen this technique used at a few cantinas and restaurants around here, but interestingly I've never heard of adding a penny to the bag. When we asked, one patio bar owner said they kept away bees; an indoor restaurant owner said it was to keep flies away. We were told something about the flies' eyes don't like the reflection of the water, or something. We've always wondered if there was really anything to it.

We've never seen this done anywhere else.

[http://users.livejournal.com/purplebunnie_/]

Northern Cali chiming in!

[aemiis-zoo.livejournal.com]

Mythbusters should totally test this out!

[kryptyd.livejournal.com]

I don't want to jump the gun having done no research on the matter, but I'd say your BS detector is spot-on today.

I've never heard to the fly thing, but in the early 90s plastic bottles filled with water were extensively used here to keep dogs off lawns. The most popular one seemed to be the green 7up bottle, but I also saw lots of clear ones. I know one hourse that still uses them. And the substance inside was just plain water, nothing foul-smelling. Even to the kid I was at the time the whole thing seemed completely ridiculous and illogical

[kryptyd.livejournal.com]

That should be "house" not "hourse". I'm ALWAYS doing that typo lately for some reason

[nutmeg.livejournal.com]

Some people will make anything up.

I bet evil fairies that enter homes through bags of water hung off the floor started spreading this rumor.

It's a good thing you are putting a stop to this or we might be overrun with evil fairies.

Whew.

[http://users.livejournal.com/purplebunnie_/]

I've never put pennies in my bags. A sandwich bag, 1/2 full of clear water, hung near doorways or windows. Yes, it really bloody works, and I don't know how. You have to change the bags out every couple of months; they must get dusty or sumpin.

[badnoodles.livejournal.com]

My PI tested this on and around dairies, a major source of house flies. The general consensus is that it doesn't do squat.