OK not confirmed, but heard it works from multiple party's
1
Fill a large, durable plastic bag with clear, fresh water. This water, with its capacity for refracting and reflecting light, will be perceived by flying insects as high optic flow. Flying insects avoid regions of high optic flow in order to prevent collisions. As a result, a simple bag of water can serve as a sort of insect lighthouse, warning it away from rocky shores.
2
Place a shiny penny into the bag, the shiner, the better. This penny should only increase the amount of reflection (optic flow) put off by the bag. Multiple pennies may work even better, so long as they increase the amount of reflective material in the bag. Don't add so many, however, that they're liable to strain or break the bag.
3
Seal the bag, or tie the opening securely shut with a piece of string or cord that measures at least a few feet long. The cord should be strong enough both to hold the full weight of the bag, and to survive extended use and exposure to weather and wind.
4
Hang the bag outside a doorway, from the limb of a tree, or anywhere that you are have a bothersome fly population. Make sure the bag is in the sun, or exposed to a significant amount of light. Ideally, the bag should be exposed to a gentle breeze that will rock the bag to and fro. This movement allows the bag to catch and reflect even more light, turning it into even more of a warning beacon for bothersome insects.
5
Monitor the bug population, to see if your "insect repellent" has any effects. Folk remedies such as this are hardly an exact science and results can vary. If you have no success, try hanging the bags in different locations. With as low-cost a remedy as this, feel free to hang multiple bags if you feel that one just wasn't enough.
