Bumblebees are much more unstable when they hover than when they fly fast. (Credit: © Den / Fotolia) Enlarge

Mar. 14, 2013 — Bumblebees are much more unstable when they hover than when they fly fast, according to new research published this month in the Journal of Theoretical Biology.


The authors of the paper, Na Xu and Mao Sun from Beijing University of Aeronautics & Astronautics in China, used a mathematical model to analyze the way bumblebees fly at different speeds, showing that the bumblebee is unstable when it hovers and flies slowly, and becomes neutral or weakly stable at medium and high flight speeds.

The instability at hovering and low speed is mainly caused by a sideways wind made by the movement of the wings — a 'positive roll moment'. As the bee flies faster, the wings bend towards the back of the body, reducing the effect of the sideways wind and increasing the stability of its flight.

According to the authors the results could be useful in the development of small flying machines like robotic insects.

"Dynamic flight stability is of great importance in the study of biomechanics of insect flight," said Mao Sun. "It is the basis for studying flight control, because the inherent stability of a flying system represents the dynamic properties of the basic system. It also plays a major role in the development of insect-like micro-air vehicles."

In recent years, with the understanding of the aerodynamic force mechanisms of insect flight, researchers have been devoting more effort to the area of flight dynamics.

The study further refutes the persistent misconception that, according to physics, bumblebees shouldn't be able to fly. The fallacy can be traced back to Le Vol Des Insects (Hermann and Cle, Paris, 1934) by French entomologist August Magnan — on page 8 he mentions bumblebees, stating, "First prompted by what is done in aviation, I applied the laws of air resistance to insects, and I arrived, with Mr. Sainte-Laguë, at this conclusion that their flight is impossible."

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