Bumblebees Flight Mysteries
Did you know that a bumblebee can carry its own body weight in nectar when it flies?
Researchers at The University of California, Davis may have partly solved the mystery of how they do this. Stacey Combes, who is an associate professor in the Department of Neurobiology, Physiology and Behavior, along with biologist Susan Gagliardi, decided to investigate how this works. They wrote a paper that was published in the journal Science Advances.
By attaching small pieces of solder wire to the bumble bees they could perform experiments by altering their body weight. Then they measured the amount of energy the bees burned as fuel while flying in a test chamber. Combes noted that the heavier their load, the more economically they flew, therefore not burning as much energy, which made little sense to the scientists from an energetics point of view.
This 2:55-minute video from the lab of Professor Combes shows a bumblebee carrying extra weight flying in a test chamber.
How do the bumblebees do this? There are two possible ways.
The increased load may cause them to increase how far their wings flap, formally known as “stroke amplitude,” when they carry a heavy load. But this does not explain how they can support the extra weight. They appear to be able to generate more lift and increase energetic expenditure by increasing their wing beat frequency.
The other way is still somewhat of a mystery. It entails the bumblebee using a different flight mode that lets them carry heavier loads while using less energy than when they engage in increased flapping. This, the scientists refer to as economy mode, and may involve the manner in which the wing rotates to reverse direction in between flight strokes.
In their published paper, they noted that some bumblebees used other mechanisms to enhance force production, when they were heavily loaded or already performed a previous flight, rather than increasing wing velocity more by elevating flapping frequency. Higher wing beat frequency may help the bee avoid obstacles and maintain aerial stability.
This video shows some amazing bumblebee footage and is just under 5-minutes long:
One might ask why they don’t always fly in economy mode if this spares the bee’s energy resources. There is no known answer yet. It may simply be that the manner of flying is entirely the bee’s preference.
Combes reminds us that all bees are unique and make independent decisions. She notes that when she started out in her profession, people saw bees as identical little machines that all do the same thing the same way, every time.
Human perspective has evolved, and we have more appreciation now for bees and their behavior. We see them as unique creatures that do as they please. Not only are they not all identical, the same bee may choose to act differently on two different days, flapping its wings in an entirely different pattern. Gone are the days when we thought we had it all figured out, that if they carried a certain weight load, they would do it the same way every time.
The bumblebee continues to delight us as it slowly reveals its secrets.
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