Sequence learning by honeybees

Abstract

Bees of several genera make foraging trips on which they visit a series of plants in a fixed order. To help understand how honeybees might acquire such routes, we examined whether (1) bees learn motor sequences, (2) they link motor instructions to visual stimuli, (3) their visual memories are triggered by contextual cues associated with the bees' position in a sequence.

• 1. Bees were trained to follow a complex route through a series of obstacles inside a large, 250 cm by 250 cm box. In tests, the obstacles were briefly removed and the bees continued to fly the same zig-zag trajectory that they had when the obstacles were present. The bees' complex trajectory could reflect either the performance of a sequence of motor instructions or their attempt to reach fixed points in their environment. When the point of entry to the box was shifted, the bees' trajectory with respect to the new point of entry was relatively unchanged, suggesting that bees have learnt a motor sequence.

• 2. Bees were trained along an obstacle course in which different flight directions were associated with the presence of different large patches of colour. In tests, the order of coloured patches was reversed, the trajectory followed by the bees was determined by the order of colours rather than by the learnt motor sequence suggesting that bees will readily link the performance of a particular trajectory to an arbitrary visual stimulus.

• 3. Bees flew through a series of 3 similar compartments to reach a food reward. Passage from one compartment to the next was only possible through the centre of one of a pair of patterns, e.g. white + ve vs. black — ve in the first box, blue + ve vs. yellow -ve in the second, vertical + ve vs. horizontal — ve in the last. In some tests, bees were presented with a white vs. a vertical stimulus in the front compartment, while, in other tests, the same pair of stimuli was presented in the rear compartment. Bees preferred the white stimulus when tested in the first compartment, but chose the vertical stimulus in the last compartment. Bees reaching a compartment are thus primed to recall the stimulus which they normally encounter there.

We argue that the elements which are linked together to form a route are “path-segments”, each of which takes a bee for a given distance in a given direction.