INSECT MOTION DETECTORS MATCHED TO VISUAL ECOLOGY

To detect motion, primates, birds and insects all use local detectors to correlate signals sampled at one location in the image with those s ampled after a delay at adjacent locations(1-10) These detectors can a dapt to high image velocities by shortening the delay(11-13). To inves tigate whether they use long delays for detecting low velocities, we c ompared motion-sensitive neurons in ten species of fast-flying insects , some of which encounter low velocities while hovering. Neurons of be e-flies and hawkmoths, which hover, are tuned to lower temporal freque ncies than those of butterflies and bumblebees, which do not. Tuning t o low frequencies indicates longer delays and extends sensitivity to l ower velocities, Hoverflies retain fast temporal tuning but use their high spatial acuity for sensing low-velocity motion. Thus an unexpecte dly wide range of spatio-temporal tuning matches motion detection to v isual ecology.