SWISH! The swatter sweeps through the air at the fly aloft. But the fly dodges the swatter, buffets for a moment in the turbulence, rights itself and then, by flipping over and landing upside down on the ceiling, mocks your crude attempt to liquidate it.
A fabulous piece of flying! Indeed, the ubiquitous fly family boasts the most aerobatic fliers in the insect realm, thanks in part to two marvelously engineered balancing appendages called halteres.
Like tiny reeds with knobs on the end, the two halteres protrude from a fly’s thorax, just behind its two wings. (See illustration on next page.) When a fly’s wings begin to beat, the halteres also begin to beat—at the same frequency, hundreds of times every second. Halteres, in fact, are like tiny gyroscopes that help the insect to fly.
They send signals to the fly’s brain whenever the fly changes its direction, as when the little fellow is buffeted by a gust of wind or by the flurry of a swatter or a newspaper that whistles by perilously close. The halteres tell the fly instantly that its body has yawed, rolled, or pitched, just as the gyroscope in an aircraft tells the pilot the same things, albeit far less perfectly. The fly quickly and easily corrects its flight.
Unlike conventional spinning gyroscopes, halteres look more like pendulums. But they do not hang or stand vertically relative to the fly; they protrude from its side. Once set in motion, halteres, like pendulums, tend to keep oscillating, or swinging, in the same direction or plane in obedience to the laws of motion. So when the fly’s body changes its orientation in space, exterior forces twist the oscillating halteres at their base, where nerves sense the twist. The brain analyzes these nerve signals and automatically directs the wings to right the fly—all at lightning speed.
Halteres, in fact, are one of the special assets unique to flies, a two-winged family of some 100,000 kinds that includes horseflies, houseflies, blowflies, fruit flies, tsetse flies, sand flies, and crane flies. Their ingenious gyroscopes give flies a degree of aerial maneuverability that outstrips that of any other family of flying insects. Indeed, this oft-despised insect gives proof of the Creator’s scientific genius.
Animals/Jim Harter/Dover Publications, Inc
Awake 1999 published by Jehovah’s Witnesses
© Kjell B. Sandved/Visuals Unlimited