Printed in Great Britain CONTRIBUTION OF COMPOUND EYES AND OCELLI TO STEERING OF LOCUSTS IN FLIGHT

Locusts (Orthoptera, Acrididae) were tethered inside a simulated horizon visual display. Rotation of the horizon elicited following motions of the animal's head and rudderlike movements during flight. Head and steering motions were still elicited after either the compound eyes or the ocelli were surgically ablated. Head motions after ocellar cautery suggested that the ocelli may function synergistically with the compound eyes to (a) minimize the delay of visual responses and (b) augment visual responses when no sharp horizontal border is present. Flight steering motions were found not to depend on proprioception of head position. Three other species (Diptera and Odonata) also followed horizon rotations with head motion after their compound eyes had been ablated