The e-mail reminded me of the bags of water that hung above the patio door half filled with water that she claimed helped reduce the number of flies in the area. I never totally understood how this worked but after receiving the e-mail I started thinking about it. Then some friends invited my daughter and me to go to dinner with them at our local Barbecue restaurant, Island BBQ, located around the corner from our home. Since my wife was out of town taking care of her parents I figured this was a great way to feed us without the mess and cleanup and work involved in cooking. When we got there our friends were sitting on the open air back patio next to the meat cookers. Hanging everywhere were baggies with water in them.
While we sat there and ate our food we only saw one fly inside the area. He was not even messing with our food as I think he was mesmerized by the water hanging in those bags.
I did some checking and the consensus seems to be that the water creates a reflection that the flies many lenses in their eyes, approximately 8000, detect movement extremely well. They may actually see these reflections of water as potential harm and stay away. One person also said to add a few pennies to the bags as this causes even more reflection.
Whatever these little bags do I can say for a fact that they do work and will now hang some around the doors of our house to keep those pesky critters out of the house.