Landing Reaction of Musca domestica, IV: A. Monocular and Binocular Vision; B. Relationships between Landing and Optomotor Reactions

Abstract

Abstract 1. The behaviours of monocular and binocular flies are compared with respect to the landing reaction. It is found that landing reaction is elicited through different mechanisms by stimulating the zones of single or of double vision: Monocular stimulation in the field of single vision evokes reactions with both ipsilateral and contralateral leg s; monocular stimulation in the field of double vision evokes reaction only with the ipsilateral legs. 2. T he relationships between landing and optomotor reactions are analyzed. It is found that, a. W hen the fly is not free to turn itself, it may react to a lateral displacement in the visual field (optomotor stimulus) with a landing reaction ; b. The threshold for landing evoked by an expansion in the visual field (landing stimulus) is much low er than the threshold for landing evoked by a lateral displacement; c. A horizontal lateral displacement in the visual field of an eye is adequate to evoke the landing reaction only if it is perceived in the direction from the front to the back of the eye; d. W hen the fly is free to turn itself, it can present both landing and opto­motor reactions to a optomotor stimulus; e. W hen the fly is fixed at a point, landing reaction can be evoked also by an escape stimulus.