Bumblebees More Stable In Flight Than When Hovering
March 15, 2013

Bumblebee Flight Stability Is Diminished When Hovering

Lee Rannals for redOrbit.com - Your Universe Online

Researchers wrote in the Journal of Theoretical Biology about how bumblebees are actually more unstable when they hover rather than when they fly fast.

Na Xu and Mao Sun from Beijing University of Aeronautics & Astronautics in China analyzed the way bumblebees fly at different speeds by using a mathematical model. Their model showed that the bumblebee is unstable when it hovers and flies slowly, and becomes neutral or weakly stable at medium and high flight speeds.

According to the researchers, the instability seen when a bumblebee is hovering and or flying at low speed is caused by a sideways wind made by the movement of the wings. As the bee flies faster, its wings bend towards the back of the body, which reduces the effect of the sideways wind and increases the stability of its flight.

The authors say the results may be useful when developing 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."

The team looked at bumblebee flight using the same methods as used in quantum mechanics. When considering wing size and shape, body mass, and upwards and downwards forces, the team was able to make a stability analysis of the flapping flight of an insect mathematically. Using this mathematical model rather than studying live bees allowed the team to be more accurate when analyzing the mechanical flight.

"The computational approach allows simulation of the inherent stability of a flapping motion in the absence of active control, which is very difficult, even impossible, to achieve in experiments using real insects," Sun further explained.

Researchers used a model of a bumblebee with wings about the same size and shape as a real bee. The outline they used of the body was about the same as that of a bumblebee.

In past studies, researchers looked at the hovering flight dynamics of different insects. However, this perspective didn't consider forward movement, and the forces created by the wings. The latest study considers both vertical and horizontal movement to determine how stable the flight is overall.

The researchers say they plan to conduct further research into the area to compare the stability of flight at different speeds of bumblebees and drone flies.

Bumblebee populations have been facing rapid declines in the US, and are getting closer to becoming extinct. In 2011, researchers wrote in the Proceedings of the National Academy of Sciences that bumblebees range in the US has shrunk by as much as 87 percent, and numbers have fallen 96 percent.

Scientists also published in the journal Science at the beginning of March this year about how the loss of wild bees is having negative consequences for crop harvests. The team found that managed honeybees are not as successful at pollinating crops as wild insects. Pollinating insects add to the production of 84 percent of European crops, so not having these wild bees will eventually cause major problems for farmers.