Why do insects have eyes with thousands of lenses?

Most adult insects, including bees and dragonflies, have two large compound eyes, made up of separate, sometimes thousands, of lenses. They all point in different directions to give the insect a very wide field of vision. The lenses also help the insect see movement, enabling it to react quickly to seize its prey or escape danger. You can witness this yourself as you try to swat a fly in your home—it’s almost impossible to catch a flying insect!

Flies and many other types of insects have compound eyes with thousands of lenses, unlike human eyes, which only have one lens.