Why People Hang Pennies in a Bag of Water Outside Their House

If you live somewhere with flies, you’re probably eager to find ways to get rid of them. After all, they’re both a nuisance and a potential hazard to your health. There are a plethora of remedies out there, all with varying degrees of success. But one you may not be familiar with involves hanging up some pennies in a bag of water on your porch. It sounds peculiar; does it even work? We looked into it for you.

How Does This Hack Work?

There are plenty of theories on why this hack might work, and most of them have something to do with how house flies see. According to pest control service Orkin, house flies have compound eyes that “can recognize even the slightest movements in a wide field” and “detect and react to movement at a quicker pace than species with simple eyes.” So if a house fly sees something moving, it will react to the potential danger much faster than a human could.

So, how does this relate to pennies and a bag of water? It has to do with reflections. Putting pennies in a bag of water creates a lot of reflective surfaces. When sunlight hits the water, it refracts. Adding pennies into the mix means that light has many more surfaces available to bounce off. So, the theory goes, having all that light interacting with a house fly’s sensitive compound eyes probably either overwhelms the fly or leaves it thinking there’s a lot of movement and that the area isn’t safe.

Does the Penny Bag Hack Actually Work?

Snopes has fact-checked this theory but came back with inconclusive results. Some folks swear it works, but others see no difference in the results. For example, this hack has been tested multiple times, including on Mythbusters, where it didn’t work. Still, Snopes pointed out that testing it in a controlled studio setting differs from testing it in natural light.

While it isn’t a proven pest control hack, there’s no harm in trying it yourself. It’s relatively cheap to set up, and if you have kids it can even be a fun science project for them to try with you. There’s even a few variations of this hack that you could try if you’re so inclined. You could compare just a plain bag of water, a bag with one penny, a bag with several coins, and others with other shiny inclusions such as foil.

Source

• Snopes: “Do Water-Filled Baggies Repel Flies?” (2009)
• Orkin: House Fly Eyes

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