Flowers and bumblebees have evolved together. Bumblebees rely on flowers for nectar, and flowers depend on the bees to pollinate them.

Scientists have known for a long time that the bright colors on flowers help attract bees and are an aid in bringing bees and flowers together.  In fact, bees can see colors in the ultraviolet range on flowers; these colors are invisible to the human eye.

It’s not just color and scent that will cause a bumblebee to land on a flower.  Researchers have recently discovered that a plant’s electric charge also acts as an attractant for the bee.

Professor Dominic Clarke and his team at the School of Biological Sciences discovered that bees can detect electric fields emitted by flowers. Flowers usually have negative charges.   At the same time, bees tend to pick up positive charges when they are flying. Because of their small size, bumblebees are affected by tiny charged particles in the air. When the bees collide with these particles, the bees lose electrons and gain positive charges.

When a positively charged bee approaches a negatively charged flower, the flower and the bee develop an electrical attraction to one another. This attraction is not great enough to cause a spark, but according to the researchers, the bees are able to sense it.

In a paper published in the February 21 online edition of Science, Clarke and his colleagues revealed that bumblebees can distinguish the electric field of one plant from that of another, and that when they were taught how to distinguish between two colors, they learned more quickly when were given electric signals as clues.

Clarke’s team created artificial flowers, some of which had positive electric fields. Those with positive fields contained sucrose, a tasty and nutritious bumblebee treat. The other flowers contained a solution of bitter-tasting quinine.

The bees learned how to distinguish between the flowers. Once the scientists shut off the electric fields, the bees chose flowers at random, indicating that they were using the electric charges to distinguish the ones with sucrose from the ones with quinine.

The researchers also found that after a bee lands on a flower, the flower’s electric potential changes for a few minutes.  This could act as a signpost for other bees, telling them that another bee has just visited that flower.

The bees were also able to distinguish between differently shaped electrical fields.

Daniel Robert, a member of the team thinks that a flower’s electric field might exert a force on a part of a bumblebee’s body, such as its hairs, and that is how it senses the field.

If this is so, bees are not the only animals with organs that they can use to sense electricity.  The lateral lines in sharks and some bony fish contain receptors, called ampullae of Lorenzini, that can sense electric fields.