Bumblebees’ Little Hairs Can Sense Flowers’ Electric Fields

Flowers generate weak electric fields, and a new study shows that bumblebees canactually sense those electric fields using the tiny hairs on their fuzzy little bodies.

“The bumblebees can feel that hair bend and use that feeling to tell the differencebetween flowers,” says Gregory Sutton, a Royal Society University Research Fellow atthe University of Bristol in the United Kingdom.

People used to think that perceiving natural electric fields was something that animalsonly did in water. Sharks and eels can do it, for example. The platypus and spinyanteaters were the only land critters known have electroreceptive organs, but thesehave to be submerged in water in order to work.

Then, a few years ago, Sutton and his colleagues showed that bumblebees could senseelectric fields in the air.

“There is, all the time, a background electric field in the atmosphere,” says Sutton,”Any plant that’s connected to the ground will generate its own electric field just byinteractions with the atmosphere.”

He wondered if bumblebees could sense those electric fields and use them in someway. So his team tested that idea with the help of a bunch of almost identical artificialflowers.

The scientists took half of the flowers and put 30 volts on them, then filled them withsugar water. The other flowers were filled with a bitter liquid. “And the bees willeventually learn to go to the ones that are charged to 30 volts,” says Sutton.

When they turned off the voltage, the bees lost the ability to differentiate between theflowers and began to forage randomly, showing that the bees really were relying onthose electric fields.

But how were the bumblebees able to sense them? That’s what the researchers tackedin their latest study, described in the Proceedings of the National Academy of Sciences.

“We used a laser beam that could measure small motions of an antenna or a hair, andthat’s how we measured how much the air and the antenna moved in response to anelectric field,” says Sutton.

They also stuck a very fine electrode wire into the nerve at the socket of the bottom of ahair to record the activity of nerve cells there.

“They’ve got these really fuzzy hairs all over their body, and when they approachsomething with an electric field, that electric field will bend the hairs on their body,”says Sutton. And that bending generates a nerve signal.

The results suggest that bumblebees can sense an electric fields produced by a flowerthat’s up to 55 centimeters (nearly 22 inches) away. But that’s under ideal conditionsin the lab—Sutton says 10 centimeters or so (about 4 inches) is more likely in the realworld.

“I’m very excited by this because these little mechanically-sensitive hairs are commonall over the insect world,” says Sutton. “I think this might be something we see in moreinsects than just bumblebees.”

“Basically this just adds to the long list of incredible things that bees can do,” saysRobert Gegear, who studies pollinating insects at Worcester Polytechnic Institute inWorcester, Massachusetts.

He says it’s unclear if bees really use electric fields in the real world, where flowershave a ton of other compelling features like color and smell.

“And so the one question I have is ‘What is the functional relevance?’— not just fromthe bee side but from the plant side as well,” says Gegear.

For all we know, Gegear says, bumblebees may detect electric fields for something thathas nothing to do with flowers, like navigation or communication.