Inexpensive fly control?

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.

Doorways of Brookline

We walked the dogs while there was still some light out, so these have a little different feel to them.
( eight more )

On this day in 365 Urban Species: cranberry viburnum.