Species-specific spectral tuning of motion vision in butterflies.

Color provides an important visual dimension for object detection and classification. In most animals, color and motion vision are largely separated throughout early stages of visual processing. However, accumulating evidence indicates crosstalk between chromatic and achromatic pathways. Here, we investigate the spectral sensitivity of the motion-vision pathway at the level of pre-motor descending neurons (DNs) in two butterfly species with different retinal compositions and wing coloration. Butterflies engage in fast, agile flight within often colorful visual ecologies, which may heighten evolutionary pressure to integrate color and motion vision. Indeed, we observed a separation of spectral sensitivities that matches the functional properties of butterfly DNs, such that wide-field, optic flow-sensitive DNs involved in stabilization reflexes have effective broadband spectral responses, while target-selective DNs involved in target tracking are comparatively narrowband and match conspecific wing coloration. Our findings demonstrate the spectral tuning of motion vision within a pre-motor neuronal bottleneck that controls behavior. VIDEO ABSTRACT.