Pattern vision of the honeybee ( Apis mellifera): the significance of the angle subtended by the target

Abstract

The Y-choice apparatus, in which freely flying bees choose one of two targets from a fixed distance, was modified by adding a transparent baffle in each arm to control the angle subtended by the target at the point where the choice is made. Black and white patterns were partially covered to see whether the bees use the centre or the periphery of a target, and with what cues. A new technique, testing trained bees with one or more black spots on an otherwise blank target, probes the memory of the spatial distribution of black areas within the patterns. The results show that bees discriminate the orientation cues averaged over medium-sized regions in each part of a target, including the periphery subtending up to 100 ° at the point of choice. With large patterns, although the bees remember the predominant edge orientation in well separated areas of the image, they primarily use the spatial lay-out of black areas in the margin irrespective of the edge orientations. Confirming the above, the discrimination of a large right-angled cross from the same pattern rotated in the vertical plane by 45 ° depends upon its angular size, and the principal cues are the locations of the ends of the arms.