5. The Buzz On Bees By Jen Waters (The Washington Times)

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 manoeuvre, says James Bell, an aerospace engineer at the National Aeronautics and Space Administration's Ames Research Centre in Mountain View, California. 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."

Using the research of how a bee flies, scientists have begun to design unmanned air vehicles that are the size of an insect, Mr. Bell says. These instruments, which could be used by the military, would fly by flapping their wings like an insect. Better understanding of how bees navigate would be important for these projects because the goal would be to make them self-steering.

It is understood that bees use motion detection to navigate, a method called optic flow. Although bees cannot see the colour red, the insects have internal compasses that detect the polarization of sunlight and ultraviolet sensors to track the horizon, which helps them measure movement. Bees have five eyes, including two compound eyes with 7,000 hexagonal facets. The other three are simple eyes that discern light intensity. The faster an item moves by a bee, the closer the bee is to the item. Bees are designed to manoeuvre so the image speed remains constant, preventing them from running into things. Because they don't know their airspeed or height, motion detection helps bees perform such tasks as landing on flowers.

To comprehend how bees navigate during flight, scientists need to research further how the insects' brains, which are the size of a sesame seed, work, says Michael Dickinson, professor of bioengineering at California Institute of Technology in Pasadena. "It's capable of doing some rather extraordinary things," Mr. Dickinson says. "It's being controlled by a remarkable, tiny computer."