The evolution of color vision in insects

We review the physiological, molecular, and neural mechanisms of insect col or vision. Phylogenetic and molecular analyses reveal that the basic baupla n, UV-blue-green-trichromacy, appears to date back to the Devonian ancestor of all pterygote insects. There are variations on this theme, however. The se concern the number of color receptor types, their differential expressio n across the retina, and their fine tuning along the wavelength scale. In a few cases (but not in many others), these differences can be linked to vis ual ecology. Other insects have virtually identical sets of color receptors despite strong differences in lifestyle. Instead of the adaptionism that h as dominated visual ecology in the past, we propose that chance evolutionar y processes, history, and constraints should be considered. In addition to phylogenetic analyses designed to explore these factors, we suggest quantif ying variance between individuals and populations and using fitness measure ments to test the adaptive value of traits identified in insect color visio n systems.