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Bees can sense flowers’ electric fields, say researchers

Researchers from the University of Bristol have discovered that bees and plants are able to communicate via electric signals. Communication between bees and flowers is crucial, as bees play an important role in maintaining natural plant communities and ensuring productions of seeds in most flowering plants.

“Insects use several senses to forage, detecting floral cues such as color, shape, pattern, and volatiles. We report a formerly unappreciated sensory modality in bumblebees (Bombus terrestris), detection of floral electric fields,” write the researchers in the study’s abstract. “These fields act as floral cues, which are affected by the visit of naturally charged bees. Like visual cues, floral electric fields exhibit variations in pattern and structure, which can be discriminated by bumblebees.” 

Flowers often generate bright colors, patterns and attractive smells to draw the attention of their pollinators. However, Professor Daniel Robert and his colleagues discovered that flowers also produce patterns of electrical signals that can communicate information to the insect pollinator. The researchers note that these electrical signals can work simultaneously with a flower’s other signals to enhance the flower’s “advertising power.”

Plants are typically charged negatively and emit weak electric fields, according to researchers. Bees, on the other hand, obtain a positive charge as they move through the air. As a bee approaches a charged flower, a small electric force builds up that can transmit important information.

By locating electrodes in the stems of petunias, the researchers revealed that when a bee lands, the flower’s potential changes for several minutes. Researchers found that bumblebees can detect and distinguish between different floral electric fields, suggesting that the flower’s potential changes because the plant is signalling to bees that another bee has just visited.

“Because floral electric fields can change within seconds, this sensory modality may facilitate rapid and dynamic communication between flowers and their pollinators,” write the researchers.

They note that when bees were given a learning test, they were quicker at learning the difference between two colors when electric signals were also present.

The researchers are not certain how bees detect electric fields, although they speculate that hairy bumblebees bristle up under the electrostatic force.

Without the ability to sense a flower’s electric field, a bee might visit a flower that lacks nectar.

“The last thing a flower wants is to attract a bee and then fail to provide nectar: a lesson in honest advertising since bees are good learners and would soon lose interest in such an unrewarding flower,” says Professor Robert. “The co-evolution between flowers and bees has a long and beneficial history, so perhaps it’s not entirely surprising that we are still discovering today how remarkably sophisticated their communication is.”

The study’s findings were published in Science Express.