Headline Dec 26, 2014/



TO MOST PEOPLE , bumblebees are charming, slightly absurd creatures that blunder through garden and meadow with neither the steely determination of the honeybee nor- the malevolent intention of the wasp.

If you are a plant, though, things look rather different   -for from the point of view of some flowering plants many bumblebees are nothing more than thieves. They rob them of their nectar and give nothing in return.  

Nectar Robbery, in which a bumblebee carves a hole in the side of a flower as a bank robber might cut his way into a vault, was discovered by Charles Darwin. This technique lets bees get at the nectar-

Of flowers whose shapes have evolved to encourage their pollination by insects with long tongues, which can reach down narrow tubes.

Some bumblebees do have such tongues. But some do not. Short-tongued bees are, however, unwilling to deny themselves the bounty of nectar inside these flowers. Hence the hole cutting.

By breaking in in this way, though, a bumblebee nullifies the  100m-year-old pact between flowering plants and insects: that the plant feeds in exchange for the insect pollinating the plant. 

The question about nectar robbery that has intrigued biologists from Darwin onwards is whether the behaviour is innate or learnt. Darwin though originated the idea that many behaviour patterns:

Are products of evolution by natural selection, suspected that it is learnt. Insects, in other words, can copy what other insects get up to. Only now, though, has somebody proved that this is true.

The observations were made by David Goulson  -then at the University of Stirling, now at the University of Sussex-   and his colleagues. To test his ideas he had to go from Britain to Switzerland, for only there he could find a flower of the correct shape to conduct the study.

His crucial observation was that when the flowers of an alpine plant called the yellow rattle are robbed, the entry holes  -because of the structure of the flower- tend to be unambiguously on either the right-hand side or the left-hand side.

Moreover, preliminary observations suggested that the holes in flowers in a single meadow are often all made on the same side. This led him to speculate that bumblebees in a particular area do indeed learn the art of nectar robbery from one another-

And then copy the technique with such fidelity that they always attack a flower from the same side.

His team monitored  13  Alpine meadows during the summers of 2009 and 2011. They painstakingly recorded the sites of robbery holes in yellow-rattle flowers, and studied the behaviour of  168  bumblebees.

They tried to follow each bee until it had visited 20 flowers, though they lost sight of some insects before they had reached the score. If they could, they then captured the insect so as not to follow it again on another location.

Dr Goulson found, as he reports in Behavioural Ecology and Sociology, that two short-tongued  bumblebee species which live in the area,  Bombus lucorum and Bombus wurflenii. demonstrated handedness when they robbed flowers.

Moreover, if one species was behaving in say, a left handed manner, the other was likely to do the same. This suggests that one specie can learn from another - a trick previously thought to be confined to vertebrates.

Handedness, in any given meadow, Dr Goulson found, increased as the season progressed. But each summer appeared to start as a blank state. The handedness that developed in a meadow in 2009 did not predict its handedness in 2011.  

The most reasonable explanation, Dr Goulson argues, is that each year a few bumblebees which have learnt the trick of nectar robbery in the previous season come out of hibernation and start robbing flowers again.

By chance, they make more holes on one side of the flowers than the other, and as the habit is picked up by other, newly hatched bees, a preference for  left or right spreads by a process of positive feedback.

The bees have, in other words, created a simple culture. It is a criminal culture, admittedly. But no one ever said that nature was pretty.  

With respectful dedication to all Students of Entomology and related sciences. See Ya all on !WOW!  -the World Students Society Computers-Internet-Wireless:

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SAM Daily Times - the Voice of the Voiceless


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