Bees using secret trick to make plants flower, leaving scientists baffled

Scientists have discovered a new technique that bumble bees use to make plants flower earlier.

When faced with a shortage of pollen, bumble bees will damage plant leaves by eating them in order to make the plant flower earlier – sometimes as much as a month before it would flower naturally for tomato plants.

The researchers were not able to replicate the results by damaging plant leaves themselves, suggesting that there is a distinct characteristic to the bees’ biting that stimulates flowers. While the bees managed to make the plants flower 30 days earlier, scientists only managed to make them flower five days earlier than they would otherwise.

Using their mandables and tongue, the worker bees made holes in multiple plant species but did not use the tissue for any purpose, such as making their nests.

Wild worker bees from other species damaged the flowerless plant patches, which implies the behaviour is not unique to Bombus terrestris, the latin name for the most prominent species of bumble bee in Europe.

“We really tried to replicate with the best of our ability,” Prof Consuelo De Moraes, from ETH Zurich, the public research university in Switzerland which conducted the research, told the BBC.

“It's possible that the bees also have some cue that they are providing to the plants that is specific to the bee. And that could be secretions that we don't know about but it's something that we plan to investigate.”

Researchers have said that the damage is done in a distinctive manner – semi-circular incisions – that can be found on various plant life.

“One of the students was saying that they were eating a salad the other day, and they saw that kind of damage on the leaf that was probably from a bumblebee,” said Dr Mark Mescher, another author from ETH Zurich.

Alongside Dr Mescher and Professor De Moraes, the research was carried out by Foteini G. Pashalidou, Harriet Lambert, and Thomas Peybernes.

An explanation that has not been confirmed, but that the scientists are considering, is that it is not the bees determining the flowering of the plants but rather the plants themselves, as the reproduction of the flora is dependent on its pollen being spread when pollinators – such as bees – are in the vicinity.

It is also possible that plants have evolved a new strategy to flower when they detect a bee damaging its leaves.

On a global scale, one of the reasons bees might be behaving in this manner could be climate change. “Increasing weather events and extreme temperatures help push bees out of sync with flowers, which explains some of the dramatic losses,” said Ms Lambert.