Honey bees rob flowers after observing conspecifics and carpenter bees

Abstract Individuals may add to their behavioural repertoire by observing conspecifics, and possibly heterospecifics. Here we test Darwin’s intriguing hypothesis that honey bees rob nectar from flowers after observing the behaviour of other bees. We trained naïve honey bees to forage for sucrose by entering the flower-tube opening of custom designed 3D-printed model flowers before exposing individual bees to experimental flowers. In these flowers, nectar could only be accessed via a small hole at the base of the corolla tube, thereby simulating secondary nectar-robbing. Bees had to change their foraging behaviour from foraging via the mouth of the flower to foraging from the tube-base to rob. Different demonstrators were used to indicate the presence of a robbing hole. To explore the efficiency of information transfer from different demonstrators, we moved dead conspecific and heterospecific (carpenter bees and crickets) demonstrators towards this small hole to imitate nectar robbing. Differences in the ability and speed of honey bees to imitate robbing behaviour were recorded for each demonstrator treatment. Naïve honey bees switched to robbing behaviour more frequently when observing honey bee and carpenter bee demonstrators than when observing cricket demonstrators or controls that lacked a demonstrator. However, honey bees switched to robbing behaviour significantly faster after observing conspecifics than after observing any other demonstrators. This study demonstrates that honey bees can gather information from conspecifics and even heterospecifics while foraging, which can influence foraging behaviour such as flower robbing. Utilizing foraging cues from other individuals may lead to conspecific and heterospecific learning. “I can hardly doubt they [honeybees] were profiting by the workmanship and the example of the humble-bees: should this be verified, it will, I think, be a very instructive case of acquired knowledge in insects.” Darwin 1841