June 8, 2009

Bees trade energy for safety in winds

Harvard University scientists have determined some bees brace themselves against wind and turbulence by extending their hind legs while flying.

Wind is a universal part of life for all flying animals, Assistant Professor Stacey Combes said. Yet we know remarkably little about how animals navigate windy conditions and unpredictable airflows, since most studies of animal flight have taken place in simplified environments, such as in still air or perfect laminar flows.

Combes and Robert Dudley of the University of California-Berkeley studied 10 species of wild orchid bees in the Panamanian jungle. The researchers set up air jets and then, using high-speed video, measured the bees' maximum flight speed as they were buffeted by varying levels of turbulence. In every case, the bees displayed a side-to-side rolling motion at high flight speeds, negotiating the turbulence by extending their rear legs while in flight.

This increases the bees' moment of inertia and reduces rolling, Combes said, much like a spinning ice skater who extends her arms to slow down.

Combes said such stabilizing behavior is likely to be seen across Hymenoptera, the order of insects that includes bees, wasps, ants, and sawflies, and that turbulent airflow may decrease the flight performance of many other flying insects as well.

The study appears in the Proceedings of the National Academy of Sciences.