Fly visual systems work best in blue light. This color is the most intense and interesting to flies. Their eye’s two types of photoreceptors feed information indiscriminately into this special circuit. The other kind of photoreceptors shuttle information to a separate pathway that is color blind.
Flies have the same visual system as mammals, but their eyes are shaped differently. Their compound eyes have about 3,000 ommatidium. That makes their visual input total about 6,000 complex structures. In addition to color, the fly can distinguish between polarized light and ultraviolet light.
The color preference of insects differs depending on how the color is measured and described. In general, most color perception studies use human concepts of brightness, hue, and chroma. This does not mean that insects cannot see colors of other species, however. In fact, they can tell the difference between colors without the help of a label.
A fly’s ability to detect ultraviolet light is similar to how it perceives food. As a result, it’s likely that its attraction to certain colors may be unrelated to the color’s appearance. Similarly, flies’ liking of black is likely to be related to its association with camouflage. In addition, a fly’s love of black isn’t just a taste, it’s also an effective way of protecting itself against predators.
The researchers found that female and male flies were attracted to different colors on a color contrast disc. Females were attracted to green-purple discs while males were attracted to blackred discs. They also found no difference in preference for adjacent colors.