In the 1930s French scientists determined that bees could not fly. They knew, of course, that the insects could and did. But according to their calculations, this feat was aerodynamically impossible. They based that conclusion on the fact that wings as small as a bee's could not possibly produce enough lift to allow the bee to get airborne. The problem was, they presumed that the bee's wings were stable, like an airplane's, when in fact honeybees flap and rotate their wings 240 times a second. This flapping, along with the supple nature of the wings themselves, allows a bee--or any flying insect, for that matter--to create a vortex that lifts it into the air. But the specific aerodynamic mechanics of that process as it pertains to the honeybee, with its stubby wings, has remained a mystery until now.
New research from Michael Dickinson of the California Institute of Technology and his colleagues finally explains how Apis mellifera flies. Unlike other flying insects, honeybees use short wing strokes of less than 90 degrees and a high number of flaps every second to stay aloft. The researchers found that when challenged to fly in difficult conditions, such as a mixture of oxygen and helium that mimicked air density at more than five miles up in the atmosphere, the bees resorted to wider strokes but maintained the same high flapping frequency.
This means that honeybees are using a wing stroke pattern that is less efficient than the broader strokes and slower flapping of fruit flies and other insects, despite their constant foraging for food and other necessities. But it also means that a bee can generate more lift when it needs to--when it must carry a heavy load, for example. The researchers speculate that this odd set of strokes may have arisen from precisely this need, as the social creatures sometimes must fly while burdened with nectar or larvae. A report detailing the new findings is being published online this week by the Proceedings of the National Academy of Sciences.