Yaw-Correcting Postural Changes in Locusts*

Abstract

Changes in the angle of the relative wind sensed by the facial wind receptors of a locust evoke fast rudder-like movements of the abdomen and legs whose magnitudes are proportional to the change of wind angle. This system is sensitive to the angular velocity of the wind change. Such wind changes also evoke rotations of the head about the long axis of the body. The head rotation induces, through proprioception by the cervical hair receptors, slow, redundant rudder-like movements of abdomen and legs. Control elements for the fast movements of abdomen and legs and for the head rotation appear not to be precisely co-ordinated and seem to include no proprioceptive ‘crosstalk’. All these responses are evoked by wind-angle changes only if the insect is flying at the moment, suggesting that flight closes a neuronal switch. Separate motor pathways seem to be employed for the abdomen’s rudder-like response to wind-angle change, head rotation and turn tendency.