How good are compound eyes?
Surprising facts • A dragonfly has 30,000 ommatidia in each eye. • The body of Ophiocoma wendtii, a type of brittle star, is covered with ommatidia, turning its whole skin into a compound eye! • Compound eyes first appeared on Earth more than 500 million years ago. We know this because they can be seen on fossil trilobites of this age. Compared with single-aperture eyes, such as the human eye, compound eyes have poor resolution so they are not good at making out detail. On the other hand, compound eyes have a very large angle of view and the ability to detect fast movement and, in some cases, the polarization of light. Insects that can fly well, such as honey bees and flies, or that catch prey, such as dragonflies or preying mantis, have specialized zones of ommatidia. These zones are organized into a fovea area that gives acute vision. In the acute zone, the eye is flattened and the facets are larger, which allows more ommatidia to receive light from a spot and thereby achieve higher
