Pennies In Bags of Water Make Flies Flee

The latest talk across Facebook pages these days is how to prevent flies at your next cookout. I don’t mean the Fly family that lives down the road, but the insect variety that seems to know just when you have the drinks poured in your favorite summer plasticware so they can drop in and wash their filthy little paws (if that is what flies have) before doing the backstroke in your special southern sweet tea fruit drink. It seems there are a lot of outdoor events being decorated with plastic bags filled with water these days to frighten these bug-eyed creatures away. The bags may even contain pennies, small bits of aluminum foil and other shiny items to make the redneck water globes even scarier to the disease-laden insects. Restaurants across Mexico have been using this inexpensive project to protect their guests for a while and now many of our Tennessee citizens are giving it a try at their back porch get-togethers this summer with some success. I have even heard of a few schools doing the same in some classrooms this year and if it works to keep flies away in the spring just before a rain shower, then add more Ziplocs to next year’s education budget statewide.

So how does a plastic bag filled with water drive flies away you may ask? Some have said it magnifies the pennies resembling another insect’s eyes, scaring the fly away, while others say the clear liquid looks like the surface of a body of water, which the flies perceive as a place they don’t want to land. The best explanation is simple light refraction going through the bag of water that confuses the housefly. If you will remember your biology from days in school, a housefly has large complex eyes made up of thousands of simple eyes that don’t move or focus. The fly bases his movement by light and the refracted light coming through the water in the plastic bag confuses the fly causing him to move on to a place that is easier on the eyes. And when you have a few thousand to deal with at one time, the easier, the better. At least this is the explanation that some entomologists are giving to this new insect remover now spreading across the Internet and making its way to backyard gatherings. However, others are calling it old wives’ tales and modern superstition. But, if it works, don’t knock it. Maybe come fall we can develop some bags with college logos on them and sell them for tailgating at ballgames. You know, where there is a fly there may be a wave.

Flies are not the only insects causing trouble right now either. Mosquitoes are becoming a problem as hot summer temperatures bring more people outdoors to work and play. So far, no one has found a plastic bag of water to work on keeping them away so the Tennessee Department of Health is reminding all Tennessee residents to take steps to help prevent illnesses associated with mosquitoes. West Nile is a virus that can be carried by mosquitoes and prevention is the first line of defense. Tennesseans should take precautions to protect themselves from West Nile Virus and other diseases transmitted by mosquito bites. Mosquitoes most likely to transmit WNV bite at dawn and dusk. The best way to prevent WNV infection is to avoid mosquito bites. Here are some tips from the Department of Health that can help.

  • If you must go outside during dawn and dusk, use insect repellent or wear long sleeves, long pants and socks.
  • If possible, eliminate standing water near your home. Many containers, even those as small as a bottle cap, can hold enough water for mosquitoes to breed.
  • Keep windows and doors closed or cover them with screens to prevent mosquitoes from entering your home.
  • Use insect repellents containing either DEET, Picaridin, oil of lemon eucalyptus or IR3535. There are guidelines for using the suggested insect repellants. Neither DEET nor Picaridin should be used on infants younger than two months old. Oil of lemon eucalyptus should not be used on children younger than two years of age. DEET at 30 percent concentration is the maximum level recommended for children and infants over two months old. None of these products should be applied around the mouth or eyes.

The mosquito population is now at its peak in Tennessee and can remain active through October. It is important to take precaution and prevent mosquitoes from biting. If you need more information about the West Nile Virus, visit the TDOH Web site at