The bumblebee, with its stout body and seemingly small wings, appears to defy the conventional principles of flight. This perception isn’t new; back in the 1930s, French entomologist August Magnan famously declared bumblebee flight to be aerodynamically impossible. This intriguing notion has since captured public imagination, persisting despite readily observable evidence to the contrary.
While a casual observer might question Magnan’s assertion, elucidating the physics behind bumblebee flight requires the expertise of scientists like Michael Dickinson, a biology professor and insect flight specialist at the University of Washington. Dickinson and his team have dedicated significant research to unraveling this long-standing puzzle.
“The fundamental question of how these diminutive wings generate sufficient lift to keep these insects airborne has been largely answered,” Dickinson explained to Life’s Little Mysteries. “While some finer details remain under investigation, the core enigma of bumblebee flight is no longer a mystery.”
Dickinson’s pivotal 2005 study, published in the prestigious journal Proceedings of the National Academy of Sciences, shed significant light on the mechanics of bumblebee flight. Utilizing high-speed photography to meticulously observe actual bumblebees in flight and employing force sensors on a scaled-up robotic bee wing operating in mineral oil, Dickinson’s research revealed a crucial misconception that likely misled Magnan and others. The prevailing assumption was that bumblebees flap their wings primarily up and down, similar to birds. However, Dickinson’s findings unveiled a different reality. “In fact, with very few exceptions, bumblebees flap their wings predominantly back and forth,” he clarified.
To visualize this unique wing motion, imagine extending your arm to the side, parallel to the ground, with your palm facing downwards. Now, sweep your arm forward. As your hand reaches in front of your body, rotate your wrist upwards, flipping your palm to face upwards. With your palm now facing up, sweep your arm backwards. As you reach behind you, rotate your wrist again, returning your palm to the downward-facing position for the next forward stroke. Repeat this motion. If you were to introduce a slight tilt to your hand throughout this process, Dickinson explains, you would be replicating the fundamental wing-flapping motion of a bumblebee.
{youtube yRE2rMIXvyU}
The fluid dynamics governing bumblebee flight diverge significantly from those that enable airplanes to soar. Airplane wings are designed to deflect air downwards, generating an upward force that lifts the aircraft. In contrast, insect flight, particularly that of bumblebees, operates on a more complex principle. Dickinson describes the bumblebee wing motion as akin to a partial rotation of a “somewhat inefficient” helicopter propeller. Crucially, the angle of the wing during this sweeping motion creates vortices in the air – essentially, miniature hurricanes. The centers of these tiny vortices exhibit lower pressure than the surrounding air. By maintaining these swirling eddies of air above their wings, bumblebees effectively generate lift and remain airborne.
Further investigations have corroborated the reality of bumblebee flight. Notably, a visually compelling 2001 project conducted by a Chinese research team led by Lijang Zeng at Tsinghua University employed a fascinating method. They carefully attached minute fragments of glass to bees and subsequently tracked the reflected light as the bees navigated a laser array. Building upon these fundamental discoveries, contemporary research is increasingly focused on the intricate mechanisms by which insects achieve control and maneuverability once airborne. These advanced studies hold particular significance for the burgeoning field of robotic insects, including the development of robobees by researchers at Harvard University and other institutions, promising exciting applications in various domains.
