Control of hindlimb posture by wind-sensitive hairs and antennae during locust flight.

Steering movements of tethered, flying locusts, Schistocerca gregaria, subjected to simulated yaw were examined under open-loop conditions. Lateral movements of hindlimbs or curling of the abdomen were monitored with a capacitive movement transducer and were interpreted as indicating the tendency of the animal to turn. Three responses to simulated yaw were noted: Yaw-correcting upwind turning tendencies (Figs. 1, 2, 3). Downwind turning tendencies (Figs. 2, 3, 4, 5), and transient adjustments of hindlimb position consistent with an upwind turning tendency occurred in animals that made either no sustained postural adjustments of hindlimbs, or that exhibited sustained downwind turning tendencies (Figs. 4, 5). Ablations of certain mechanoreceptors tested their roles in wind detection and wind angle determination. The expression of upwind turning tendencies, whether sustained or transient, depends on inputs from cephalic mechanosensory hairplates (Figs. 2, 3, 4, 5). With hairplates occluded, all locusts exhibited downwind turning tendencies. All downwind turning tendencies depend on inputs from the antennae (Figs. 2, 3). Antennae and hairplates operate in an apparent antagonism in the steering responses they produce, which may provide the control flexibility required for complex flight maneuvering.