Figure 1.

(a) Experimental set-up consisting of two flight arenas (100 × 70 cm and 30 cm high) randomly used for either pretraining foraging (with Perspex feeders) or training (two differently coloured feeder types) to which a colony was connected via a bifurcated Perspex tunnel allowing for controlled access to the arenas by means of shutters. (b) The positions of the feeder colour loci in the hexagonal bee colour space determined by the responses each colour elicits on the bee's ultraviolet (u), blue (b) and green (g) photoreceptors (Chittka, 1992). The distances (hexagon units) between these colour loci were 0.061 (yellow-green), 0.189 (purple-blue), 0.333 (blue-yellow) and 0.391 (purple-green). (c) The four colour pairs comprising the two training groups (A, B). CS⁺ and CS⁻ indicate the rewarding and nonrewarding conditioned colour stimulus, respectively. Each colour set was used until 50 feeder visits (after the first correct choice) were recorded, after which the next colour set in the sequence was presented. Each bee was trained on one of the two colour sequences only.