Buzz-pollinating bees deliver thoracic vibrations to flowers through periodic biting

Pollinator behavior is vital to plant-pollinator interactions, affecting the acquisition of floral rewards, patterns of pollen transfer, and plant reproductive success. During buzz pollination, bees produce vibrations with their indirect flight muscles to extract pollen from tube-like flowers. Vibrations can be transmitted to the flower via the mandibles, abdomen, legs, or thorax directly. Vibration amplitude at the flower determines the rate of pollen release and should vary with the coupling of bee and flower. This coupling often occurs through anther biting, but no studies have quantified how biting affects flower vibration. Here, we used high-speed filmography to investigate how flower vibration amplitude changes during biting in Bombus terrestris visiting two species of buzz-pollinated flowering plants: Solanum dulcamara and Solanum rostratum (Solanaceae). We found that floral buzzing drives head vibrations up to 3 times greater than those of the thorax, which doubles the vibration amplitude of the anther during biting compared with indirect vibration transmission when not biting. However, the efficiency of this vibration transmission depends on the angle at which the bee bites the anther. Variation in transmission mechanisms, combined with the diversity of vibrations across bee species, yields a rich assortment of potential strategies that bees could employ to access rewards from buzz-pollinated flowers. [Display omitted] •Buzz-pollinating Bombus terrestris vibrate flowers with mandibles while biting•Anther biting reduces mandible vibrations but enhances flower vibrations•Enhanced flower vibrations should facilitate increased pollen release•Biting behavior is a crucial component of buzz pollination Woodrow et al. show that buzz-pollinating bees transmit thoracic vibrations to flowers via the head during a periodic anther biting behavior. This is facilitated by a flexible mechanism in the neck. The angle of biting, and the geometry of the flower, dictate the effectiveness of this vibration transfer.