- The Washington Times - Wednesday, June 4, 2003

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.”

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 color 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 maneuver 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.”

Making honey is among the remarkable things the insects can do, says George W. Imirie Jr. of Rockville, president of the Montgomery County Beekeepers Association. In fact, honeybees are the only insects that make food for humans. During the life span of a worker honeybee, which is an average of six weeks, it makes about 1 teaspoons of honey.

“Even though I sell a lot of honey, I have never been very interested in producing honey for sale,” says Mr. Imirie, who has raised bees for 71 years. “That has not been my prime interest. So little was known about honeybees that I wanted to find out more about bees.”

For bees to make honey, the nectar from various plants is carried in their honey sacks. While the nectar is in the honey sack, the bees add an enzyme called invertase to it that breaks down the sucrose into glucose and fructose. The bees return to the hive and perform a dance that communicates the direction, distance and amount of food available for the other bees. The nectar brought back to the hive is placed in a cell by the bees. Then the insects evaporate the moisture by fanning their wings.

Once the moisture content in the cell is about 18 percent, the bees cap the hexagonal cup with wax flakes produced from the bottom of their abdomens. They place the wax on top of the cells to protect their food for the winter. The bees also use their wax to build the honeycomb in which the cells exist.

Aside from creating honey, bees perform an important service by pollinating many of the world’s crops, says Dave Morris, president of the Bowie-Upper Marlboro Beekeepers Association, which meets at Watkins Park Nature Center in Largo.

For instance, plants such as carrots, peaches, broccoli, watermelons, cotton, berries, cucumbers, lima beans, squash, apples and almonds benefit from the pollination of bees. In fact, bees pollinate about 30 percent of all food humans eat.

“It’s a marvelous little insect,” Mr. Morris says. “They are not really that intelligent, but their activities are triggered by instinct. … We’re still discovering all these things about them. Their behavior is amazing.”

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