Bags of water hung from the ceiling can repel flies.
This myth is based in the theory that refracted light in water confused flies’ compound eyes.
The Build Team made a rig consisting of three chambers separated by trap doors. The first chamber would hold the flies, the second would hold some rotten meat, and the third would hold both rotten meat and a bag of water. They then released over 5,000 flies from the first chamber and waited to see how many flies would go into each of the other two. After the chambers were sealed off, they let all the flies die and collected the corpses to weigh for comparison. The chambers with and without the water contained 35 and 20 grams of flies, respectively, busting the myth.
It works,my wife is from Belize,they use this method with out the pennies.
We use this method in our garage. Florida summers are fu*king brutal,and the flies are freaking crazy during the day. You have to change the water out periodically,and of course it doesn't work at night,When's the last time you saw a house fly at night?