The honeybee ( Apis mellifera) detects bilateral symmetry and discriminates its axis

Abstract

Honeybees were trained and tested with a choice between a black and white pattern composed of two pairs of equal orthogonal bars with bilateral symmetry and the same or a similar pattern with a different symmetry. The targets subtended < 50 ° at the point of choice. Earlier results with the chevron pattern revealed that discrimination of rotation is improved when one of the patterns is bilaterally symmetrical about a vertical axis. Bees were trained on 7 different pairs of 4-bar patterns at the same time, taken successively to prevent the bees from learning any one pattern. The bees learned to discriminate a pattern with bilateral symmetry from one without symmetry, irrespective of the orientation of the axis of symmetry. They also discriminate between a pattern with one axis of bilateral symmetry and the same pattern rotated by 90 °, irrespective of the actual pattern. Although the patterns are regularly changed during the training, the bees distinguish the axis of bilateral symmetry. When trained on one set of patterns, the bees also discriminate the axis in the same or other patterns rotated through 180 °, when all bars have moved over to the other side, showing that they have not remembered one side of the pattern with each eye. For one pattern, the angular tuning curve for the discrimination of the axis of symmetry falls from a score of 80% correct on-axis to near 67% at 15 ° off-axis and 50% (random) at 30 ° off-axis.