With huge, globular eyes that make up about 50% of their head, dragonflies are amazing visual predators.
A sampling of beautiful dragonfly eyes from a Google search
And those eyes are key to their success as highly visual predators.
Halloween Pennant dragonflies search from the tips of the highest plants in grassy fields, with their orange-banded wings fluttering in the breeze.
In fact, they are probably the most efficient predators in the animal kingdom, with an astounding 95% success rate per attempt. In comparison, lions are lucky to succeed once every four to five tries and great white sharks only manage to catch what they are after half the time. How do dragonflies do it?
Here’s looking at you… the facial disk of the Horned Clubtail. Depending on the angle of incoming light (and observer position), the eyes might look turquoise blue.
The eyes and more particularly, the wiring of retinal cells to the brain, is key to their hunting success.
Those giant optical domes on the top of their heads give them a 360 degree view, and contain as many as 30,000 optical units (ommatidia), each with a complement of photopigments that can process images separately. Thus, instead of one retinal focusing area, they have thousands.
The eye of a dragonfly, showing the individual facets or ommatidia that contain visual pigments. Each facet can detect and send an image to the insect’s brain. Imagine having 30,000 eyes! From Science Blogs, July 8, 2009.
In addition, where human eyes have three photo pigments, dragonflies have 15-30 pigments that can detect light in ranges beyond human capability, including detection of polarized light. What if we could see images in UV or infra-red, or whatever other spectral wavelengths dragonflies can resolve?
A newly emerged male Common Whitetail has the wing markings of a male and the abdominal coloration of the female. Over the course of the next week, he will gradually transform to the powder-white abdomen typical of males.
Photopigments sensitive to blue and UV light are concentrated in the upper part of the compound eye, so that prey (or predators) above them stand out against a perceived white background. Pigments sensitive to longer wavelengths (green, yellow, red) are concentrated in the lower part of the compound eye and allow prey flitting below the dragonfly in dense vegetation to be detected.
This Dot-tailed Whiteface continually moved its head up and down as it scanned for prey. Each time I tried to get in front of it to photograph its white face, it flew away.
In addition to their heightened visual sensitivity and acuity, dragonflies exhibit single-object tracking, which means they keep a particular prey item exactly on a collision course with themselves. (Kind of sounds like a drone, doesn’t it?)
And that’s where the fancy flying comes in handy. To keep the image of the prey in exactly the same place in their visual field, a dragonfly might fly up, down, sideways, backwards, even upside down, if needed. Four wings that can move independently facilitate this maneuverability, and in fact, they don’t even need all four.
This female 12-spotted Skimmer has lost half of its left hind wing, but it’s doubtful that it comprises hunting success.
These amazing little machines have been around for several hundred million years, feasting on slower flying, less visually talented prey. Such a visual formula for hunting success ensures that they will be around for a while, keeping those pesky mosquitoes in check.
[This is an edited version of a previous post from Backyard Biology]