Bumblebees Bite Plants To Make Them Flower Early, Scientists Discover
Scientists from Switzerland have found a new – and very clever – behaviour practised by bumblebees, which tricks plants into flowering up to 30 days earlier than they usually would.
This new study found that, when deprived of pollen, bumblebees will nibble at the leaves of flowerless plants, making tiny yet effective incisions.
The damage done to the leaves tricks the plant into flowering early, allowing bees to get the nutrients required while building their summer colonies. In instances where pollen is readily available, the bees will not bite the plants.
For the study, published in Science on May 22, lead author Foteini G. Pashalidou and colleagues put flowerless tomato and black mustard plants inside mesh cages, alongside colonies of pollen-deprived buff-tailed bumblebees.
The team then took the plants away after worker bees made five to 10 punctures in the leaves. These small holes led to the black mustard plants flowering two weeks earlier than normal, while the tomato plants flowered a month sooner than would usually be expected.
Researchers were also able to compare bee behaviours by placing both pollen-fed and pollen-deprived bumblebees in mesh cages with the flowerless plants and observing them.
Worker bees from pollen-fed colonies rarely bit the flowerless plants, while the pollen-deprived colonies were noted to do so.
In a bid to make sure that results weren’t simply on account of artificial lab conditions, bumblebee colonies were placed on a Zurich-based rooftop in March 2018, along with various flowerless plant species.
The bees were able to forage as far afield as they pleased, and yet it was found that they would leave bitemarks on all the nonflowering plants closest to their hives.
The frequency of this behaviour faded toward the end of April, coinciding with the time more local flowers were once again coming into bloom. Scientists believe this establishes that the bees’ leaf-biting activity is driven by pollen availability.
The bees used their proboscises and mandibles to make distinctively-shaped puncture marks in the leaves, but did not eat the material or use it for their nests.
Co-author Dr Mark Mescher told BBC News:
I think everything that we’ve found is consistent with the idea that the bees are damaging the plants and that that’s an adaptation that brings flowers online earlier and that benefits the bees.
Interestingly, when researchers attempted to copy the damage inflicted on the plants by the bumblebees they were unable to achieve the same results.
Going forward, scientists hope these findings will be useful for finding out more about the resilience of bumblebees, a species which is facing changing environments and threats to their very survival.
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