charge – GOLLYGEE!

Here at GOLLYGEE! we’ve been following the news on bees and electric fields.

We learned last month that flowers use electric fields to guide bees their way. Bees pick up a positive charge from the static they encounter while flying through the air. Flowers, like most plants, conduct electricity toward the ground and have a negative charge at their surfaces. When bees encounter a flower, the negatively charged pollen is attracted to their positive charge. And when they leave, other bees can tell the flower was just visited because of the reduced electric field.

Yesterday, Ed Yong at Not Exactly Rocket Science reported that bees also use electric fields to facilitate social interaction:

Greggers created Pavlov’s bees. He exposed them to artificial electric fields that mimicking those found in the hive, before giving them a rewarding sip of nectar. Soon, he found that the field alone was enough to make them extend their tongues in anticipation of a tasty treat, just like Pavlov’s dogs salivating at a the sound of a bell.

Greggers found that the bees detect these fields with their flagella—the very tips of their antennae. Picture a bee, dancing away in a tightly packed hive with many neighbours in close proximity. As it waggles, it also vibrates its wings. As the dancer’s positively-charged wing get closer to a neighbour’s positively-charged antenna, it produces a force that physically repels the antenna. As the dancer’s wing swings back to its original position, the neighbour’s antenna bounces back too. With their electric fields, the bees can move each other’s body parts without ever making contact. (Sure, the beating wing also pushes air past a neighbour’s antenna, but Greggers found that the force produced by the incoming electric field is ten times stronger.)

The bee detects these forces with small touch-sensitive fibres in the joints of their antennae, which send electrical signals towards the insect’s brain. If Greggers immobilised the joints by covering the antennal joints with wax, the bees couldn’t learn to associate electric fields with nectar rewards.

These signals from the fibres are intercepted and processed by a structure called Johnston’s organ within the antennae. By recording the activity of neurons in this organ, Greggers showed that it does indeed fire when an electrically charged object—like a Styrofoam ball—is brought close to the flagellum.

Head over to Not Exactly Rocket Science for more. Or read the research paper here.

We all know that flowers attract bees and other pollinators to help them reproduce. And in this week’s Science magazine, we get more insight into how it’s done. As it turns out, bees use the electric fields around flowers to sense whether it might contain pollen. The bees can also tell by the electric field whether a flower has just recently been visited by another bee.

Plants tend to conduct electricity into the ground. This gives the flowers at the top a slight negative charge compared to the air around them. Bees on the other hand pick up positive charges as they fly around. These charges are caused by friction with the air and between body parts. When bees touch the flowers they attract the negatively charged pollen particles from the flowers. And the electric field of the flower is reduced so that when the next bee flies by it can tell that it has just been visited.

A computer model of the electric potentials around a flower

Researchers studied this phenomenon setting up electrically charged disks to stand in as flowers. Half of the disks contained sugared water and the other contained quinine, which is the bitter substance that gives tonic water it’s flavor. When the disks weren’t charged, bees landed on the disks at random landing on the bitter flowers just as often as the sweet ones. But when the sweet disk was charged, they visited it with 81% accuracy. They used the electric charge to hone in on the sweet “flowers”.

In addition to this, the plant conducts electricity, as the bee comes in closer proximity and eventually touches the flower. And once the bee leaves, the change in the plants electric field remains changed for about 2 minutes, as it build up negative charge again. During this period, the reduced electric field may serve as an indicator for other bees to know that the flower has just been visited so that they don’t stop by the pollenless plant.

Much more at the link, including how they use the electric field as an aid in determining shapes.

Source: D.Clarke et al. Detection and learning of floral electric fields by bumblebees. Science. Published online February 21, 2012

GOLLYGEE!

Tag: charge

bees, socialization and electric fields

bees, flowers and electric fields