bees – GOLLYGEE!

03.27.2013

bees, socialization and electric fields

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.

03.08.2013

links

Two links for you today:

1. Have you ever wondered how they get grapes to grow so big these days? NPR explains how farmers use a technique called girdling to force the plant to grow larger fruit. This technique along with the use of gibberellic acid, which acts as a kind of growth hormone for the plant, is the reason why the size of grapes in the supermarket is ever increasing. Check it out.

2. And now more on the topic of bees and flowers. Flowering plants use caffeine to lure bees. The New York Times reports on a study showing that flower nectar contains caffeine. Caffeine is a stimulant, and the flower uses it as a kind of reward in an operant conditioning mechanism. The bee gets rewarded with this stimulant drug after pollinating the flower. Having linked the reward to the smell and taste of the flower nectar, the bee searches out more of the flower. The study shows that caffeine helps increase the bee’s memory of the flower’s odor. Have a look!

03.01.2013

more on bees and pollination

NPR helps us continue our bee coverage. Today they summarize these two studies on wild bees and pollination. The first study examines the importance of wild bees in pollinating crops. Wild bees are thought to be better pollinators than honey bees and to help boost crop harvests:

Farmers who grow these crops often rely on honeybees to do the job. But scientists are now reporting that honeybees, while convenient, are not necessarily the best pollinators.

A huge collaboration of bee researchers, from more than a dozen countries, looked at how pollination happens in dozens of different crops, including strawberries, coffee, buckwheat, cherries and watermelons. As they report in the journal Science, even when beekeepers installed plenty of hives in a field, yields usually got a boost when wild, native insects, such as bumblebees or carpenter bees, also showed up.

“The surprising message in all of this is that honeybees cannot carry the load. Honeybees need help from their cousins and relatives, the other wild bees,” says Marla Spivak, a professor of entomology at the University of Minnesota. “So let’s do something to promote it, so that we can keep honeybees healthy and our wild bee populations healthy.”

The second study brings the not so good news that wild bee species might be in decline. From NPR again:

Robertson taught biology and Greek at Blackburn College in Carlinville, Ill., and he was fascinated by the close connection between insects and flowers. He spent years in the forests around Carlinville, carefully noting which insects visited which wild flowers at what time of year.

Burkle and Tiffany Knight, a colleague at Washington University in St. Louis, went back to Carlinville to see how much of the ecosystem that Robertson observed still exists today.

Much of the forested area around the town has been converted into fields of corn and soybeans — or suburbs. In the fragments of forest that remain, Burkle and Knight found all of the flowering plants that Robertson recorded in his notes a century ago. Of the 109 species of bees that Robertson saw, though, just over half seemed to have disappeared from that area.

If you have time you can listen to the NPR story here. Or check out the research papers here and here.

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bees, socialization and electric fields

links

more on bees and pollination