Hungry Bees Nibble Plants to Prompt Early Flowering

Published on May 28th 2020
A close up of a bumblebee on a spring blossom

Like many of our essential pollinators, Bumblebees are threatened by habitat loss, increased pesticide and herbicide use, and the rise of alien species.

On top of this, rising temperatures have had scientists worried as to how insect populations will respond to climate change.
In temperate environments, Bumblebees are most active during spring and summer. Then, from early autumn, the new queens look for a suitable spot to hibernate. They begin building their new colony in the spring.
A bumble bee nest
A bumblebee nest
Many insects use temperature as an alarm clock. It tells them that spring has arrived, and hibernation is over. For this reason, insects such as bees have been emerging earlier in the year as temperatures increase.
Scientists are worried that temperature increase will offset the timing between different wildlife, including insects and flowering plants. However, some new research suggests that emerging bumblebees are finding ways to adapt to new environmental conditions.
Research from ETH Zürich has shown that bees are 'tricking' plants into earlier blooms.
A close up of bumblebees on a yellow flower
Bumblebees may have found a way to get flowers to open earlier
They first noticed random holes in plant leaves while conducting another experiment. When observing the bees, it didn't appear like they were eating the plant or taking it back to the nest, either.
The researchers soon realised that the bees were encouraging the plants to flower. It's already known that when plants become damaged, they begin to flower sooner to boost their reproductive success.
Hungry bumblebees were exposed to several Black Mustard plants. They began to chew around 5-10 holes per plant, prompting flowering 16 days earlier on average. Another experiment demonstrated that Tomato plants would flower roughly a month earlier following the bee-nibbling behaviour!
a bee on a tomato plant
Bumblebees can pollinate tomatoes through 'buzz pollination'
The hungrier the bees were, the more holes they'd chew per plant. This suggested the behaviour was hunger-driven. So far, White and Red-tailed bumblebees have been observed doing this in nature.
The researchers weren't able to replicate the results by cutting holes themselves. This means, whatever is causing the plant to flower, is because of the bees.
The next question the researchers face is: how are the bees doing this? Likewise, how and why did the behaviour evolve in the first place?

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