WHY DO BEES TURN BACK AND LOOK

The timing of learning of colour and shape of the food source, as well as of near-by landmarks, was examined exploiting a behaviour describe d recently, the ''Turn Back and Look'' behaviour (TBL): Bees departing from a novel food source after feeding turn around to view it at a sh ort distance (Figs. 2, 3) before departing for the hive. They repeat t his behaviour on several successive visits, termed the ''TBL phase'' ( Fig. 5). To examine the function of the TBL, I trained individual bees in 4 different modes. In the first 3 they could view a food source or a landmark of a particular colour or shape during (i) arrival as well as departure, (ii) only arrival, and (iii) only departure; in the fin al mode (iv) the bees viewed one colour (or shape) on arrival, and ano ther on departure. At the end of the TBL phase, the bees were tested b y offering them a choice between the visual stimulus to which they wer e trained (modes i-iii) and a different (novel) one, or between the st imulus viewed on arrival and that viewed on departure (mode iv). The t est results show that learning after feeding (while performing the TBL ), i.e. backward conditioning, occurs regardless of whether the colour (Fig. 6, Fig. 10a) or shape (Fig. 7) of the food source, or the colou r (Fig. 10b), shape (Fig. 11), and position (Fig. 12) of a near-by lan dmark is considered. Bees trained in mode (iv) preferred the stimulus learned on arrival over that learned on departure in almost all cases. However, a stimulus viewed exclusively on departure (mode iii) was of ten learned as well as when it was viewed exclusively on arrival (mode ii) (Figs. 10a, 11, 12), or both on arrival and departure (mode i) (F ig. 6). The finding that the timing of learning can be manipulated sug gests that it is not based on hard wired predispositions to learn part icular visual cues on arrival, and others on departure.