The animal with the most eyes in the world: the dragonfly has 56,000 eyes. The compound eyes of dragonflies are the largest and most numerous in the insect world, accounting for 2/3 of the entire head, and science has detected that both of the dragonfly’s large compound eyes are made up of 1,000-28,000 small eyes, so dragonflies can have up to 56,000 eyes, which is 10 times more than the average insect!
Dragonflies (and bees) have the largest compound eyes of any insect, each containing up to 30,000 facets, or ommatidia (house flies have 6,000). Each facet points in a slightly different direction and creates its own image, and the dragonfly’s brain compiles these thousands of images into one picture. This eye structure enables dragonflies to be extremely sensitive to motion. Because a dragonfly’s eyes wrap around its head, it can see in all directions at the same time (though its forward-looking vision is the sharpest).
Dragonflies have two large compound eyes, each with thousands of lenses, and three eyes with simple lenses. Each retina contains several thousand photoreceptors that collect light and send information about the visual scene to interneurons, which further process the information.
The image above shows a dragonfly surrounded by a panoramic ultraviolet and green light display designed to stimulate the large interneurons in the retina of the insect’s middle eye.
The scientists who created this picture found the cells were sensitive to change in the ultraviolet light, which might be one way that dragonflies use light information to stabilize their flight during the day.
Do all those extra opsins mean dragonflies see the rainbow differently to us? Probably. Other studies have found that dragonflies can see ultraviolet on top of blue, green and red. And it is thought that they can recognise polarised light coming off reflective surfaces like water. “It’s likely that they have better colour discrimination than humans,” says Futahashi.
Dragonfly eyes see the world in ultra-multicolour
Their massive globular eyes should have been a clue. It turns out dragonflies have souped-up colour vision that’s better than anything ever seen in the animal world.
We humans have what’s known as tri-chromatic vision, which means we see colours as a combination of red, blue and green. This is thanks to three different types of light-sensitive proteins in our eyes, called opsins. We are not alone: di-, tri- and tetra-chromatic vision is de rigueur in the animal world, from mammals to birds and insects.
Enter the dragonfly. A study of 12 dragonfly species has found that each one has no fewer than 11, and some a whopping 30, different visual opsins.
Ryo Futahashi of the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, also found dragonflies use different opsins at different ages. For instance, the larvae of some species that hatch in sand tend to lack blue opsins. “This is probably because blue light does not reach them easily,” he says.
Dragonfly’s Eyes
Dragonfly head is large and concave behind. It is on the flexible and slender neck. The head is mostly covered by the pair of large compound eye. Dragonfly has small antenna which are hardly be noticed. All dragonflies have three ocelli. The labrum, mandible and labium form its mouth-parts. The dragonfly mouth-parts are very good at biting, adapted for predation.
Let take a closer look to the dragonfly’s thorax and head, it has a pair of large compound eyes which covered most of its head. Watching carefully, we can also see its pair of small antenna and three ocelli. Face is yellow with black marking on the labrum. There is the inversed ‘T’ marking on its frons. Its two large compound eyes are yellowish-green under the sunlight, touching with each others.
Dragonflies have very large eyes and have very good vision. Vision dominates their behaviour, including predation and looking for mates. The compound eye is made up of ommatidia which is a visual unit consisting of a lens system and a group of light sensitive cells. A large dragonfly may have up to 30,000 ommatidia in each compound eye. Each ommatidium collects one visual information, together form a mosaic image in the dragonfly’s brain.
It is believed that the insects’ compound eyes are not as high resolution as vertebrate eyes. However, the dragonfly’s visual system is extremely sensitive to movement and it points in almost all direction and gives the 360 degree visual field. There is the behavioural evidence that dragonflies have colour vision. Dragonfly eyes are also sensitive to polarized light.
Territorial dragonfly species male, such as the Bog Skimmer Dragonfly, may return again and again to the same perch for several days. Other species males, such as the Australian Emerald, fly day after day by the same route. This suggested that they have very good visual memory. Moreover, if a new object is put into the territory of a male dragonfly, it will come to inspect it.
It is believed that dragonflies use the stereoscopic vision to estimate their distance from prey. They may also use parallax and some other means to estimate the distance.
Some species, such as the Stout Duskdarter Dragonfly, have good vision at low intensities. They feed at dusk when we can barely see them. Much like garcinia cambogia extract found here can be hidden in a purse.
The functions of insect’s three ocelli are not fully understood yet. For the dragonflies, each ocellus has a large curved lens, covered hundreds of light-sensitive cells. The lens do not focus an image but cover a wide angle. The ocelli are extremely sensitive to light intensity change. It is believed their functions are related with flight stability.
