For a fly, that simple
bag of water looks like lots of disco balls reflecting light and movement in a
way that causes them to be dizzy. Under such conditions, they end up being
distracted all the time and feeling vulnerable to predators.
Flies
serve as food for a number of other animals, and flies who feel vulnerable won't
stick around, because it feels too dangerous.
Not only does this
method work, it is also low-cost and harmless, unlike chemicals that can poison
our food, air and water. It's ironic how sometimes the best solutions are also
the simplest ones!