Amazing facts about dragonfly compound eyes


Picture of compound eyes of a dragonfly.


A Head Full of Eyes


If the flight of the dragonfly is extraordinary, no less can be said of its eyesight.

Two huge compound eyes almost cover the dragonfly’s head.

Each of these eyes has up to 30,000 hexagonal units that are like tiny eyes within an eye, since each one transmits a separate image to the brain.

That doesn’t mean, however, that a dragonfly sees thousands of different pictures, all at the same time.

Rather than seeing a complete picture, as we do, it senses movement, patterns, contrasts, and shapes.

All those images need analyzing.

Thus, 80 percent of a dragonfly’s brain is dedicated to assessing visual information.

Few optical systems are as sensitive—a dragonfly can spot a mosquito some 60 feet [20 meters] away.

Even at dusk, when the light is so dim that a human observer can barely spot tiny flies, tropical dragonflies easily capture them.

A dragonfly’s rapid, darting flight through riverside vegetation requires hundreds of split-second decisions.

It can handle this formidable task because it can see up to a hundred distinct images a second, over five times more than we can.

Thus, a movie, which projects 24 images a second, would just look like a series of still photos to a dragonfly.