The buzz on bees

Harry A. Mallow of Cumberland, Md., finds bees fascinating. As president of the Allegheny Mountain Beekeepers Association, Mr. Mallow has always loved the insects, especially the way they buzz from one place to another.

“It looks like they wouldn’t be able to fly, but God made them powerful enough to fly and carry a load of nectar,” he says. “They are not anything like an airplane, which is slender and can cut through the wind.”

Although scientists understand the basics of how bees fly, many of the details are still a mystery.

Bees have four wings that can be joined into two pairs when the bee wants to flap them together. The wings also can be disconnected from the thorax muscles, which enables the insects to fly, and folded over their back at other times.

The method bees use to fly is significantly different from how airplanes maneuver, says James Bell, an aerospace engineer at the National Aeronautics and Space Administration’s Ames Research Center in Mountain View, Calif.

Larger birds fly in a manner similar to airplanes, while smaller birds, such as hummingbirds, fly more like bees. The smallest insects, such as gnats, use methods that scientists don’t understand well at all.

“If you treated a bee like an airplane in a physics problem, the bee couldn’t lift its own weight,” Mr. Bell says. “The smaller you are, the easier it is to flap your wings multiple times.”

When an airplane flies, the wing is tilted to a greater and greater angle to produce more lift for a given airspeed. If the wing is tilted beyond a specific angle, which is individual to each airplane, it starts making less lift, which eventually can cause the airplane to crash.

This process, which is called stall, takes a few tenths of a second to develop. When bees fly, they flap their wings so fast in a figure-eight motion that they constantly produce the larger amounts of lift that an airplane can create only momentarily without crashing. This explains why an analysis of bee flight using conventional air-flight aerodynamics fails.

“Bees get the advantage of the high lift produced just as an airplane stalls, but bees don’t stall,” Mr. Bell says. “As the stall develops, the bee quickly drops its wing down to a lower angle where it’s not going to stall. As soon as the bee knows the air is flowing over the wing correctly, it pitches the wing angle up again.”

Scientists have reported that as bees’ wings move up and down, they produce small whirlpools in the air, called vortices, which bees use to enable flight.

“It’s constantly moving its wing to a point where the vortex lifts the wing,” Mr. Bell says. “It avoids positions where the vortex would push the wing and the bee down.”

However, more research must be done on how air flows around bee wings. Other concepts that scientists don’t understand about bee flight include the efficiency of their wings, which flap about 200 times a second. They also are researching the air-pressure distribution on a bee’s wing, which would reveal the required strength of the wing and the parts of the wings that produce lift.

“Other mysteries concern things such as the shape of the bee’s body, which appears to give the bee high drag,” Mr. Bell says. “It may be that at low speed the bee’s body is actually streamlined. Or it may be the bee puts up with a high-drag body because it’s important for other reasons that we don’t know yet.”

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