Though you may not expect it, this strange concoction quickly becomes a fly’s worst nightmare.

This fly repellent works best when coupled with a light source, so hang your bag close to an outdoor lamp.

As per reports, insecticides are based on different fragrances and smells that insects and flies hate. But this particular “repellent” has nothing to do with fragrance — and a lot more do with sight.

It appears that shiny coins in a water bag are a terrifying sight for flies.

The flies are at first attracted to the water-filled bag, but once they get closer, they quickly turn around and fly away.

What the insects see in the bag is an example of light refraction, something the human eye can handle. For an insect’s eyes, though, it’s a completely different story.

Check out more in the video below: