The Role of Certain Optomotor Reactions in Regulating Stability in the Rolling Plane During Flight in the Desert Locust, Schistocerca Gregaria

Abstract

1. Locusts given freedom of movement in the rolling plane show complete lack of stability when flown in darkness, continually rotating about their longitudinal axis. 2. Stability in this plane appears to be controlled by two optomotor reactions, a dorsal light reaction and a reaction to the position of the horizon in the visual field. 3. Locusts behave as if there is a spatial representation of the visual area in the central nervous system and always turn so that the horizon is horizontal and the brighter half of the visual field uppermost in this representation. 4. The optomotor reactions control stability in the rolling plane indirectly through head movements, the head being orientated first and the body aligned with it by differential wing movements. 5. Relative head and body movements appear to be registered by two sets of proprioceptors, hair plates borne on the first cervical sclerites where they articulate with the head and a row of tactile hairs on the under edge of the prothorax. 6. The reactions described are operative in light intensities down to 0.1 ft.-lamberts, approximately comparable to tropical twilight conditions.