June 2019
Flowers have several remarkable ways of attracting bees. Color, shape, scent, and even ultraviolet patterns can help guide pollinators toward nectar and pollen. But researchers have discovered another, less obvious signal: electric fields.
In 2013, researchers reported that bumblebees can detect and learn the weak electric fields surrounding flowers. Flying bumblebees typically acquire a positive electrical charge, while flowers are generally electrically connected to the ground and have a negative electric potential relative to the surrounding air. When a positively charged bee approaches a flower, it encounters the flower’s electric field.¹
Even more remarkably, these floral electric fields are not all identical. Researchers found that flowers can exhibit different electrical patterns and structures, and bumblebees can learn to distinguish between them. The electrical information works together with other floral signals, such as color, and can help bees identify flowers associated with a reward. A bee’s visit can also alter a flower’s electric field within seconds, potentially giving subsequent bees additional information about the flower.¹
That discovery raised another fascinating question: How does a bumblebee sense an electric field?
In 2016, several of the same researchers investigated the mechanism. They found that weak electric fields physically deflect tiny mechanosensory hairs covering the bumblebee’s body. These hairs are extremely sensitive mechanical sensors. When an electric field moves the hairs, the movement produces measurable neural activity in the bee. The researchers concluded that these sensory hairs are a site of electroreception in bumblebees.²
The system is extraordinary. A flower produces visual patterns, scents, shapes, and an electric field. A flying bee carries an electrical charge and possesses microscopic sensory hairs capable of responding to the flower’s weak electric field. The bee’s nervous system can then use this additional sensory information while deciding which flowers to visit.
What appears to us as a bee simply flying from flower to flower therefore involves a sophisticated interaction between flowers, electrical charge, microscopic sensory hairs, and the bee’s nervous system.
Sources
1. Dominic J. Clarke, Heather M. Whitney, Gregory P. Sutton, and Daniel Robert, “Detection and Learning of Floral Electric Fields by Bumblebees,” Science 340, no. 6128 (2013): 66–69. DOI: 10.1126/science.1230883. PubMed article record
2. Gregory P. Sutton, Dominic Clarke, Erica L. Morley, and Daniel Robert, “Mechanosensory Hairs in Bumblebees (Bombus terrestris) Detect Weak Electric Fields,” Proceedings of the National Academy of Sciences 113, no. 26 (2016): 7261–7265. DOI: 10.1073/pnas.1601624113. Full PNAS study
