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

Abstract

It has been suggested by several authors that optomotor responses play a part in promoting stability in flying insects (Pringle, 1957). Faust (1952) examined a variety of insects and found only the Diptera and Odonata amongst them to be fully stable in complete darkness, and experiments with blind flies having only one haltere led him to suggest that visual regulation might play some part in regulating stability in the rolling plane in Calliphora. Von Buddenbrock (1937) described a ‘Lichtruckenreaction’ in which insects orientated themselves so that the greater light intensity fell on a given region of the eye, generally the dorsal region, and which appeared to play a large part in maintaining stability in the rolling plane. Mittlestaedt (1950) analysed this reaction in greater detail in the dragonfly, Anax imperator. He showed that, when the movements of a flying dragonfly were restricted to the rolling plane, it rotated the head until the uppermost region of the eyes was maximally stimulated and then aligned the body with the head by means of proprioceptive hair plates in the neck region. The inertia of the wide, heavy head appears to give the dragonfly a dynamic sense which preserves its stability in complete darkness. In other cases visual stimuli appear to influence stability by a direct effect on the thoracic motor pattern rather than having an indirect effect through head movements (Pringle, 1957).