Can Flies See Red?

Flies have a limited color vision. Since each colour has its own wave frequency, they have trouble distinguishing between them. Additionally, flies only have two types of color receptor cells. This makes it difficult for them to distinguish between red and other colours. Hence, the question “Can flies see red?” comes up.

Drosophila’s visual pigment has a peak at 520 nm and is progressively more transmissive to longer wavelengths. In contrast, red-eyed Musca and Calliphora have a long-wavelength shift in the screening pigment. In addition, the Rh1 visual pigment is packed less densely than other flies’ screening pigments.

Fruit flies can see red and green. Interestingly, this behavior doesn’t appear to be restricted to the afternoon and early morning. Researchers also discovered that red light attracts fruit flies. The findings are intriguing because they reveal an important biological mechanism that controls the body’s circadian rhythm.

Insects, including flies, have a compound eye with thousands of visual receptors, known as ommatidia. This eye is a long, thin structure that has a lens on the outer surface and a crystalline cone structure with pigment cells and visual cells. The eye also has a nerve fiber connecting to the optic nerve. The optic nerve then relays this information to the fly’s brain.

In a recent study, researchers from the University of Washington found that the common mosquito species flew toward specific colors in response to a telltale gas that human hosts exhale. Moreover, mosquitoes ignored other colors when smelling the CO2. This suggests that a certain wavelength of the visual spectrum is better for mosquitoes than others.