The identity of the previous visitor influences flower rejection by nectar-collecting bees.

In the field, recently probed flowers of borage, Borago officinalis, typically contained little or no nectar (and hence were relatively unrewarding), whether probed by a bumblebee, Bombus spp., worker or a honeybee, Apis mellifera. However, a nectar-collecting bee was likely to reject a recently probed flower only if the previous visitor was a conspecific (honeybees) or congener (bumblebees); the effect was especially marked in honeybees. Honeybees rejected more than 80% of flowers probed by conspecifics less than 20 s previously, but less than 20% of flowers probed by bumblebees less than 20 s previously. Only if the previous bee was a conspecific or congener did the probability of a bee probing a flower increase with the time since the last probing visit. Otherwise, the probability of a bee probing was independent of the time elapsed since the last visit. Bees' reactions to flowers whose nectar content had been manipulated independently of prior visits suggested that bees were repelled from flowers by species- or genus-specific chemical cues deposited by previous bees. Laboratory studies elsewhere have reported that honeybees are repelled from artificial feeders by volatile bee-deposited chemicals. My results constitute strong evidence that such cues are used by nectar-collecting honeybees in the field, and also suggest that bumblebees respond to similar cues. Calculations show that the ability to detect recently visited flowers may help bees to make a foraging profit, especially when bee densities are high. Thus, bee-deposited chemicals may confer information and economic advantages to foraging alongside conspecifics or congeners. Copyright 1998 The Association for the Study of Animal Behaviour.