How do insects see in the dark

Posted on Nov 21, 2022      272

On a dark moonless night, the illumination may be thousands of times lower than during daytime. But while we sleep in our beds, most living creatures begin the active phase of the day. So how do they navigate in total darkness?

As an example, let’s take night insects - the size of their visual organs rarely exceeds the size of the match head, but they are well oriented on the ground in dim light, cleverly avoid obstacles and detect even weak movements around.

Imagine that at night you find yourself in a tropical forest, under the crown of which does not penetrate the light of the moon and stars. It would seem that there is no light source at all around you. But that would only be true for our imperfect visual apparatus - in fact, it would fill the space around with single photons. For the human eye, their number will obviously not be enough to get at least a dull picture of the surrounding world.

Megalopta genalis

However, the eyesight of night-time insects and animals is much more sensitive. For example, the eyesight of a Megalopta genalis tropical night bee only absorbs a few photons, but this is enough to navigate in a confusing and dense tropical forest even when the light levels are at extremely low levels. The European night butterfly of the Deilephila elpenor species from the wafer family also has a similar behavior. This would be impossible without certain tricks from an insect.

Night butterfly of the species Deilephila elpenor

On the example of the sphingidae, scientists have studied the works of the visual centers of the insect’s brain and found out that because of certain work of neurons, a butterfly can put into a single picture single photons that are caught at different points of space. As it captures more and more photons, the picture of the world in the head of Deilephila elpenor becomes brighter - it can be compared to the long shutter speed of the camera when taking photos.

Long Shutter Speed Night Photography - fixed subjects can be seen well, but moving subjects remain blurred.

True, it will not be possible to achieve a high definition of the image, but an insect can form an idea of the surrounding world and even see it in color!

This ability, which is called “neural summation”, is also available to other nighttime insects. Of course, the resulting image will be far from perfect - for example, there will be no fast-moving objects, but this way of visualizing the world shows how difficult and ingenious the visual center of even small creatures.