The reason for flies’ color change is not clear. A recent study published in the Nature journal shows that fruit flies are attracted to green light early in the morning and late in the afternoon. But at midday, they are attracted to red light, a sign of the day’s slower pace. Scientists are unsure whether the flies use the same pathway to identify different colors or if it is just a matter of preference.
The adult fly consists of three parts: a head, antennae, and three pairs of legs. The head has a pair of compound eyes, two antennae, and various mouthparts. The thorax contains the locomotor center and bears a pair of membranous wings. The legs are made of specialized tissues called pronota. The larvae are tiny and cream-whitish. Likewise, the immature forms of flies are whitish, legless, and cream-colored.
It is unclear how flies use their visual system to distinguish between different colors, but the brains of the insects are capable of discrimination at the level of a few nanometers. These small differences are sufficient for flies to distinguish between stimuli with a 20-nm difference.
This behavior may serve as a navigational behavior towards open space. In female Drosophila, for instance, females orient towards ultraviolet light when not laying eggs and turn away when they do. This behavior may depend on the flies’ internal state.