Description
A damselfly on a green stem at Oaks Bottom, tilted just enough to show the top of its head. Two enormous compound eyes, blue and black thorax, legs braced along the stem.
And between the two big eyes, in a neat triangle: three small amber beads.
Those are ocelli, and this damselfly has five eyes.
Most people never notice them, partly because you need to be looking down at the head from above and partly because nothing about them says eye. But nearly every dragonfly and damselfly carries three, arranged in a triangle on the forehead, in addition to the two compound eyes that take up most of the skull.
They do not see pictures. An ocellus cannot resolve an image at all — it is closer to a light meter than a camera. What it does instead is measure brightness, and it does so extremely fast, several times faster than the compound eyes can process a scene.
Here is what that speed is for, and it is the part I find genuinely wonderful.
From the air, the world divides into a bright half and a dark half: sky above, ground and water below. Three light sensors mounted in a triangle on top of the head, each pointing slightly differently, can therefore read which way up the insect is and how fast that is changing. Tip to the left and one ocellus brightens while another dims.
It is an artificial horizon. The signals run almost directly to the muscles that steer the wings and neck, bypassing the slower business of actually looking at anything, so the correction happens before the animal has consciously registered the tilt at all.
Aircraft carry the same instrument, and we consider it essential. This one is three specks of amber on the forehead of something that weighs less than a paperclip, and it has been in service for roughly three hundred million years.
Once you know they are there you will start tilting your head to look for them on every damselfly you meet. I certainly do.
This is a high-resolution digital download of the photograph, made at Oaks Bottom Wildlife Refuge in Portland, Oregon — yours to print for your home or office, set as a wallpaper, or simply keep. Of everything in this collection this is the one with the most hidden in it.
What you’ll receive: a high-resolution JPEG, approximately 3200 × 2976 pixels — sharp enough to print at full photo quality up to about 10.5 × 10 inches at 300 DPI, and larger at normal wall viewing distances. Delivered as an instant download the moment your order is complete.
License: Personal use only. Print it for your own home, use it as a wallpaper or screen background, enjoy it yourself. Not licensed for commercial use, resale, redistribution, or AI training. © Jonathan Swanson / JonSwan Productions. All rights reserved.