Bumblebees Bite the Leaves of Flowerless Plants, to Stimulate Earlier Flowering | Biology

The bees are based in a large extent in the pollen of the resources of the essential nutrients that build their colonies in summer. Therefore, the annual celebration of the differences in the availability of these resources must simply be tolerated, but a team of researchers from ETH Zurich and the University of Paris-Saclay made observations that suggest that bumblebees have strategies to deal with the irregular flowering season: when you are facing a shortage of pollen, bumblebees actively damaged the leaves of the plant, and this behavior resulted in an early flowering by as much as 30 days.

Bumblebee workers are faced with shortages of pollen using their proboscis, and the jaws to cut distinctive shaped holes in the leaves of the plant, with each event of damage, taking only a few seconds. Image credit: Hannier Pulido / ETH Zurich.

“Previous work has shown that various types of stress can induce flowering in plants, but the role of bee damage in the acceleration of the production of flowers was unexpected,” said co-lead author, Professor Mark Mescher, a researcher in the Department of Environmental Systems Science of ETH Zurich.

Initial observations with four species of plants revealed that the bumblebee workers use their siphons and the jaws to cut the holes in the leaves of the plant.

However, the Professor Mescher and his colleagues saw no clear evidence that the bees are actively feeding on the leaves or the transport of the sheet material back to the hive.

Then, the scientists performed several experiments and laboratory studies to the free air available in the trade, colonies of bumblebees and a variety of plant species.

They were able to demonstrate that the bumblebees tend to damage the leaves has a strong correlation with the amount of pollen that can get — the bees damage leaves a lot more frequent when there is little or no pollen available to them

It was also found that the damage caused on the leaves of the plant had dramatic effects on flowering time in two different species of plants: tomato plants subjected to bumblebee bite flowers have up to 30 days earlier than those who had not been attacked, while the mustard plant flowers around 14 days before that, when damaged by the bees.

“The bee damage had a large influence on the flowering of plants — one that has never been described before,” said co-lead author, Professor Consuelo De Moraes, also from the Department of Environmental Systems Science of ETH Zurich.

“The stage of development of the plant when it is bitten by the bees can influence the degree to which flowering is accelerated.”

The authors also tried to manually replicate the patterns of damage caused by the bumblebees to see if they could reproduce the effect on flowering time. But, while this manipulation gave rise to a little before flowering, in both plant species, the effect was not as strong as that caused by the bees themselves.

“The chemical or other cue may also be involved. Either that, or our manual of imitation of the damage was not accurate enough,” said the Professor Moraes said.

“The bees may have found an effective method to mitigate local shortages of pollen,” he added.

“Our open fields are abuzz with other pollinators, also, that they may also benefit from the bees’ efforts.”

The findings were published in the magazine Science.


Foteini G. Pashalidou et al. 2020. Bumble bees damage to the leaves of the plant and speed up production of the flower when the pollen is scarce. Science 368 (6493): 881-884; doi: 10.1126/science.aay0496

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