Stationary and dynamic responses during visual edge fixation by walking insects

Abstract

IF the visual surround of a walking animal is rotated, the animal turns in a characteristic way. With arthropods, this optomotor (optokinetic) response has usually been described in terms of the angular velocity of the body or eyestalks. The difference between these velocities—the slip speed—has been considered as the necessary visual stimulus. Most of the previous investigations of this feedback system have been carried out in open loop conditions¹. Special care was taken that the head of the tethered animal was not free to move. In this investigation, free moving animals with head movements unrestricted also show optomotor responses when no slip speed between animal and surround is present. An explanation is offered which is in accordance with investigations on the housefly, Musca domestica^2,3.