Compound Eyes With 30,000 Facets, and Almost No Blind Spot
A dragonfly's head is mostly eye, and its eye is mostly a targeting computer.
💠 Dragonfly pace — dart through it — 2 min at human speed, 20 min at sloth speed.
Each compound eye of a large dragonfly carries up to about 30,000 ommatidia, individual optical units, wrapped around the head so completely that the animal sees nearly 360 degrees at once. The only real blind spot is directly behind the neck.
The eye is not uniform. The upper half is tuned for detecting small dark objects against bright sky, with larger facets, better resolution and a bias towards blue and ultraviolet. That is the hunting half. The lower half handles colour and the cluttered world of vegetation and water below.
Colour vision goes far beyond ours. Humans have three opsin types. Dragonflies have been found with 15 to 33, some sensitive well into the ultraviolet. What that looks like from inside is anybody's guess, but functionally it lets a dragonfly pick a specific moving speck out of a bright, glaring sky.
Flicker fusion is the other headline number. Human vision merges flashes into steady light above roughly 60 hertz. Dragonflies keep resolving separate flashes up to around 300. In practical terms, a dragonfly watching a screen would see a slideshow, and a dragonfly watching your hand approach sees it moving as if through syrup.
Combine near-spherical vision, ultra-fast temporal resolution and four independently driven wings and the 95 percent hunting success rate stops sounding like a statistic and starts sounding inevitable.
1 comment
Solveig 20 minutes ago
Reading this at sloth pace, as instructed. On paragraph two. Going well.