What insect's compound eye contains up to 30,000 ommatidia?

The dragonfly is the insect whose compound eye can contain up to about 30,000 ommatidia. Each ommatidium is a small visual unit with its own lens and photoreceptor cells.

Dragonflies need this vast visual system because they are aerial predators. Their eyes cover much of the head and provide a very wide field of view, helping them detect movement and intercept flying prey. Different species have different numbers: some measured dragonflies have nearly 24,000 ommatidia per eye, while larger species can approach 30,000.

A compound eye does not produce a single sharp camera-like image. Instead, the brain combines information from thousands of neighboring units, giving the insect excellent motion detection and broad visual coverage. Dragonflies can also detect ultraviolet light and polarized light, abilities that humans lack. Damselflies are close relatives and may look similar, but dragonflies usually hold their wings flat when resting, while damselflies commonly fold theirs over the abdomen.