Sometimes you might have seen clear water bags hanging on the doors of restaurants or clinched up in backyard grilling area. You will be surprised to know that this works as an optical fly-repellant. These bags are said to drive pests away.
Entomologists have been trying to find the reason behind this. A vast majority have cited that the reason could be simple light refraction. We all know that light ray bends when they travel through water. Refraction takes place when a clear or opaque object alters the velocity of light.
A house fly is said to have a highly sensitive array of eyes which allows it to see in multiple directions at once. The insect's head mostly consists of a pair of large complex eyes, each of which is composed of 3,000 to 6,000 simple eyes. These eyes can't move or focus on objects like human eyes, but they provide the fly with a mosaic view of the world around them. Each simple eye provides one small piece of the puzzle. A housefly bases its sense of direction on the direction sunlight comes from. So when a housefly looks at this clear bag of water, it is believed that these complex, sensitive eyes experience refraction of light. Looking at it, the insect becomes confused and flies away.