Why Can Flies Not See in the Dark?

Flies are extremely fast, but when the light is low, they are unable to see quickly. Unlike our eyes, flies and mosquitoes rely on nonvisual cues to help them navigate, including wind currents. The low light level also means that they receive fewer photons, which are the particles that make up an image.

Fly vision is described as mosaic-like, with each fly ommatidium containing thousands of tiny pictures. Each of these pictures represents a different location in the ommatidium, but when viewed from a distance, they combine to form a complete image. The larger the number of ommatidia in a fly’s compound eye, the more detail the individual parts of the ommatidia can see.

It isn’t completely clear why flies cannot see in the dark, but their eyesight is actually better than ours. The difference is due to the way their eyes are designed. Fly eyes have segmented lenses that allow them to view thousands of identical images at once. This gives them a more accurate picture of reality than humans.

The speed at which images are processed in the brain varies from species to species, but flies seem to have the fastest critical flicker fusion rate.