The human visual system is trichromatic as are many insect visual systems. Humans have red, green and blue color receptor types while many insects have green, blue and ultraviolet types. The molecular basis of these color receptors are proteins called opsins. Each human receptor is characterized by a “red”, “green” or “blue”opsin protein. The three receptor types provide information to the brain that we experience as a rainbow of colors and nuances.
A group of scientists* studied opsin genes in dragonflies and found over 30 opsin genes. Many dragonflies have more than 10 opsins that are expressed at different times and places. The eyes of adult dragonflies have receptors for short wavelengths of light on the tops of the eyes and longer wavelength receptors on the bottoms. Dragonflies fly in an upright position with the top and bottom facing toward the sky and toward the ground, respectively. The receptor placements mirror the available light. The light in the sky is more intense and skewed toward shorter wavelengths. Much of the light on the ground is reflected, less intense and skewed toward longer wavelengths. Dragonfly vision, with more receptor types may be finely tuned for discriminating color patterns in the environment.
*Extraordinary diversity of visual opsin genes in dragonflies. Ryo Futahashia, Ryouka Kawahara-Miki Michiyo Kinoshita, Kazutoshi Yoshitake, Shunsuke Yajima, Kentaro Arikawa and Takema Fukatsu. 2015. PNAS 112 no. 11: E1247–E1256