Living With Color Vision

Hawk moth

Manduca Hawkmoth Resting on A Branch

Humans typically perceive color through 3 types of photoreceptors present in the retina of the eye. Each type is maximally sesitive to a different wavelength of light in the red, green and blue portions of the spectrum The brain integrates signals from the 3 receptors types and produces the sensation of color. Many insects have 3 types of color receptors, but the wavelenth sensitivity is shifted to shorter wavelengths: Green, blue and ultraviolet. However, receptor types are not evenly distributed in a compound eye. In the tobacco hornworm hawkmoth, Manduca sexta, the dorsal rim of the compound eye only has two types of receptors, green and ultraviolet, while the ventral portion of the eye has all three types, green, blue and ultraviolet.* The dorsal portion of the eye is associated with navigation, detection of polarized light and the horizon. The large dorsal area may be useful to a moth that flies in dim light. The ventral part of the eye is assoicated with finding flowers that contain nectar. We cannot know what a moth sees and senses. We can only learn what a moth is capable of seeing. The distribution of receptor types suggests that for the moth, color is not constant and varies according to which region of the eye receives the reflected light. This is very different than the human visual experience. Moths are capable of navigating in dim light. Understanding how their eye operates may help us improve navigation at night by our planes and other machines.

*Richard H. White,*, Huihong Xu, Thomas A. Münch, Ruth R. Bennett and Erin A. Grable. 2003. The retina of Manduca sexta: rhodopsin expression, the mosaic of green-, blue- and UV-sensitive photoreceptors, and regional specialization. The Journal of Experimental Biology 206: 3337-3348.
doi:10.1242/jeb.00571

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
This entry was posted in Biomaterials, by jjneal, Environment, Vision. Bookmark the permalink.

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