Influence of scent deposits on flower choice: experiments in an artificial flower array with bumblebees

Foraging bumblebees leave chemical substances when visiting flowers and the detection of these scent marks improves their foraging efficiency. Whereas laboratory studies found that scent-marks convey attraction to food sources, all field studies found foragers to be repelled by recently visited flowers. In this study we aim to resolve this conflict by implementing near-natural reward dynamics in a laboratory feeder array. When feeders were filled with small, non-replenished amounts of reward, worker bumblebees (Bombus terrestris) avoided revisiting the depleted feeders. As evidenced by a corolla replacement experiment, feeder discrimination was based on the perception of chemical cues deposited during previous visits. Pentane extracts of bumblebee tarsi acted as a repellent when applied to glass corollas, whereas pure pentane did not. We suggest that scent-marks are simple cues inherent to footprints and emphasize the importance of context to how these cues are interpreted by foraging bees.