Brainy bumblebees bite plants that feed them

Bees may be famously hard workers but a study suggests that as they forage for food they rely not only on industry but a clever gardening technique.

Researchers found that during times when pollen, their sole source of protein, is in short supply bumblebees will nibble the leaves of flowerless plants.

The damage causes the plants to accelerate the production of new flowers, giving the bees a timely food supply.

The bites, lasting only seconds, can encourage some plants to bloom 30 days earlier, a study in Science suggests. The researchers tried to mimic the bees’ behaviour, using metal forceps and razors to perforate leaves, but had no success.

‘‘It remains possible that bees inject chemicals into the plants to promote flowering,’’ Lars Chittka, a bee specialist at Queen Mary University of London, said in a commentary in the journal.

If that were the case and the bees’ secret formula could be replicated, Professor Chittka suggested that ‘‘scientists might realise a horticulturist’s dream’’ by producing a means of accelerating flowering by a month.

Experiments over several years revealed the bees’ gardening technique, including comparing the leaf-damaging behaviour of bees that were starved of pollen with others that were well fed.

The pollen-starved bees made considerable efforts to puncture holes in the leaves of flowerless plants but those from well-fed colonies rarely did.

Precisely how the damage accelerates flowering is unknown. It is possible, according to Professor Chittka, who was not involved in the experiments, that the plants interpret the bee bites as a threat from a herbivore. This might push the plant to flower before it is destroyed. ‘‘Plants are known to speed up their flowering as a response to various stressors, but there are no known examples of such a response to herbivory,’’ he wrote.

Experts are concerned that the risk of bees starving will increase because of climate change. The emergence of the insects after hibernation is strongly influenced by temperature. By contrast, flowering relies heavily on increased exposure to light as the days lengthen in spring, a pattern that does not change from year to year.

The findings will add to a broader reappraisal of the abilities of bees. Although they have less than 0.01 per cent of the brain cells of a human, studies suggest they can do basic maths and understand the concept of zero, which some experts argue eluded humans until the 7th century. One group of researchers found that they could be trained to recognise human faces, as long as they were tricked into thinking that the faces were oddly shaped flowers.˘˘— The Times

‘‘It remains possible that bees inject chemicals into the plants to promote flowering,’’ Lars Chittka, a bee specialist at Queen Mary University of London.’’ a bee specialist at Queen Mary University of London