Active vision in insects: An analysis of object-directed zig-zag flights in wasps (Odynerus spinipes, Eumenidae)

Ground-nesting wasps (Odynerus spinipes, Eumenidae) perform characteristic zig-zag flight manoeuvres when they encounter a novel object in the vicinity of their nests. We analysed flight parameters and flight control mechanisms and reconstructed the optical flow fields which the wasps generate by these flight manoeuvres. During zig-zag flights, the wasps move sideways and turn to keep the object in their frontal visual field. Their turning speed is controlled by the relative motion between object and background. We find that the wasps adjust their rotational and translational speed in such a way as to produce a specific vortex field of image motion that is centred on the novel object. As a result, differential image motion and changes in the direction of motion vectors are maximal in the vicinity and at the edges of the object. Zig-zag flights thus seem to be a 'depth from motion' procedure for the extraction of object-related depth information.