While insects have diverse photoreceptors, it is not known whether they can see the color white. Researchers have studied the color vision of honey bees, butterflies, and bats. These animals have the ability to discriminate between colors with a difference of up to four nanometers. They have also observed that some insects prefer green substrates and others, such as the butterfly Eristalis tenax, prefer yellow objects.
Flies do not have 360-degree vision, and their eyes are spherical, which makes it difficult for them to see a very wide variety of colors. While their eyes do have a limited ability to differentiate between colors, their ability to see form and movement is still highly impressive.
Using a computer, Roger inserts tiny electrodes into the photoreceptors of the flies. Using a computer screen, he then graphs the electrical currents from these electrodes. The fastest fly recorded a distinct response to the flickering light about 400 times per second. This rate is approximately six times faster than the human response.
The eyes of flies contain thousands of individual visual receptors, or ommatidia. These images are arranged in mosaic fashion, and when viewed at a distance, they form a complete picture.