Do Bags of Water on the Ceiling Keep Insects Away? If So, HOW?

Factual Questions
1

Every so often, here in Texas, I’ll come upon a bar, cafe, or Mexican restaurant with an outdoor deck that has Ziploc bags filled with water taped to the ceiling.

Whenever I’ve asked what they’re for, I’ve been told that these bags keep mosquitoes and flies away. SOMEBODY obviously thinks that works, though I’ve never noticed a decreased insect population at joints that have these water bags.

So, can anyone explain:

  1. DOES this actually work as an insect repellent? (I’m extremely skeptical, but I’ve been wrong before.)

  2. How is it SUPPOSED to work? What is there about a plastic bag full of water that’s supposed to keep flies out?

2

Mythbusters tested this one. They found it had no deterrent affect and might even have a mild attractive effect.

3

The theory behind the bags as a repellent was that the refracted light from the bags confuses insects’ compound eyes, if I recall the Mythbusters episode correctly.

4

Okayyyy… sounds like strange reasoning, but it’s some kind of reasoning nonetheless.

5

previously on SDMB

6

Cecil said it works. Because flies are skittish types and the water refracts light, causing flies to think there is more movement in the area than there is.

Can’t vouch for it though. I learned this trick from Cecil and never used it. I prefer to just have a fan going for outdoor gatherings.

EDIT: Oh, never mind. It wasn’t Cecil. Just Doug.

7

This is a very common thing to see in Mexico, where loads of “old wives tales” are believed in. Especially in warm sub-tropical and tropical regions, you’ll see them everywhere. I lived there for quite a while. . I don’t think they work at all.

8

BTW, That’s Doug Yanega, who knows his bugs. I’m surprised that he would post something unsubstantiated like that.

9

Checkpoints in Iraq sometimes had bags of clear liquid hung up, which were invariably filled with dead flies, sometimes gobs of them.

Unlike in the staff report, it would appear that the liquid attracted the flies and drowned them.

Could the substance be water impregnated with some other substance, say, sugar?