Incredible Insects Put Man’s Flying Machines to Shame
IN THE aftermath of war, journalists and military experts tend to do a lot of crowing over the sophistication of modern weaponry. They extol the virtues of “smart bombs,” laser-guided cruise missiles, and attack-helicopters with unprecedented—and lethal—maneuverability. Without question, the ingenuity behind these weapons is often remarkable. But such glowing paeans to the machinery of death rarely acknowledge a simple truth: Even the most advanced of man’s airborne wonders are primitive in design compared to the tiny flying machines that abound in creation.
Consider the cruise missile. According to The Wall Street Journal, “the cruise missile’s path is predetermined by a digitized reference map stored inside a computer processor. A zoom lens and electronic sensors keep it on course as it glides along at high-subsonic speeds, hugging the terrain.” Sounds pretty sophisticated, doesn’t it? But now consider, in comparison, a humble insect—the bee wolf.
A Tiny Mapmaker
Ben Smith, a technical editor for the computer magazine BYTE, recently wrote: “Compared to the bee wolf, the cruise missile is downright stupid.” Why? Because a cruise missile, for all its technical prowess, is fairly easy to fool. Smith puts it this way: “You just move the target, leaving behind a dummy target. Because the cruise missile destroys itself in the process of destroying its target, it never can discover that it has made a mistake.”
Fooling the bee wolf is another matter. One biologist studying these insects tried it. Noticing that hundreds of them lived in a community of identical holes along a small stretch of beach, he waited until one of them flew off, and then he quickly covered up the entrance of its home with sand. Then he waited to see if the insect could find the hole again. To his amazement, it landed unerringly by the hidden entrance and dug it out! Observing that the bee wolf habitually flew what looked like a reconnaissance pattern above its burrow whenever it left or returned, the biologist wondered if the insect could be memorizing the surrounding landmarks, making a sort of mental map.
To test his theory, he covered the hole again and this time rearranged some pine cones that were lying around it. When the bee wolf came home, it reconnoitered from above as usual and then landed in the wrong place! For a moment it was confused. Then it took off and flew another reconnaissance pattern—but this time higher. Apparently this new perspective on the problem gave the little insect some more stable landmarks to refer to, for it immediately found its hidden burrow and dug it out again.
The computer aboard a cruise missile may cost almost a million dollars and weigh nearly a hundred pounds [50 kg]. The bee wolf uses a brain about the size of the head of a pin. Ben Smith adds: “The bee wolf also can walk, dig, locate and outmaneuver its prey, and find a mate (a task that would be disastrous for a cruise missile).” Smith concludes: “Even when this year’s high-performance machines outperform last year’s model by an order of magnitude, they are still not noticeably closer to the performance of the humble bee wolf’s brain, let alone the performance of the human mind.”
Those Marvelous Wings
The same could be said of the most advanced man-made aircraft, such as attack-helicopters. Robin J. Wootton, an insect paleontologist in England, has spent over two decades studying the ways insects fly. Some insects, he wrote recently in the magazine Scientific American, “display astonishing aerobatic feats. Houseflies, for example, can decelerate from fast flight, hover, turn in their own length, fly upside down, loop, roll and land on a ceiling—all in a fraction of a second.”
Just what enables these tiny flying machines thus to outperform man-made aircraft? Well, most aircraft have gyroscopes to help them maintain stability as they maneuver. Flies have their own version of the gyroscope—the halteres, lever-shaped protrusions right where other insects have their hind wings. The halteres vibrate in sync with the wings. They guide the fly and keep it in balance as it darts about.
But the real secret, according to paleontologist Wootton, is in the insects’ wings. He writes that when he was a graduate student in the 1960’s, he began to suspect that insect wings were “far more than abstract patterns of veins and membrane,” as they were often depicted. Rather, he says, “each wing seemed to me to be an elegant piece of small-scale engineering.”
For instance, the long veins in insect wings are actually strong tubes laced with tiny air-filled ducts called tracheae. These light, rigid spars are linked together by crossveins. The pattern thus formed is more than beautiful; according to Wootton, it is similar to the lattice girders and space frames that structural engineers use to increase strength and rigidity.
Over this intricate framework is stretched a membrane that scientists still do not fully understand, beyond the fact that it is exceptionally strong and light. Wootton notes that stretching this material over the wing’s latticework helps to make the wing stronger and more rigid, much the way an artist will find that stretching his canvas over a wobbly wooden frame makes it rigid.
But the wings must not be too rigid. They must survive the tremendous pressures of beating at high speeds and must be ready to endure many collisions. Accordingly, Wootton found by examining the wings in cross section that many of them taper from base to tip, making them more flexible at the ends. He writes: “The wings in general respond to impacts not by stiff opposition but by yielding and rapid recovery, like a reed in the wind.”
Perhaps even more remarkable, the wings can change shape during flight. Of course, birds’ wings do the same, but birds use the muscles in their wings to deform them into different shapes. An insect’s muscles do not extend past the base of its wings. In this respect the insect’s wing is like the sail on a boat. To change the shape, control must come from the base, from the crew on the deck below, or from the muscles in the bug’s thorax. “But,” as Wootton notes, “insect wings are far more subtly constructed than sails and distinctly more interesting. . . . They also incorporate shock absorbers, counterweights, ripstop mechanisms and many other simple but brilliantly effective devices, all of which increase the wing’s aerodynamic effectiveness.”
Lift—The Key Ingredient
All of these, and many other aspects of the wing’s design, enable the insect to manipulate it to gain that final key ingredient for flight—lift. In fact, Wootton describes over half a dozen complex ways in which insects maneuver their wings to generate upward force.
Marvin Luttges, an aerospace engineer, has spent ten years studying the flight of dragonflies. These insects generate so much lift that the American magazine National Wildlife recently described the way they fly as “an aerodynamic miracle.” Luttges attached tiny weights to one variety, called the widow, and found that the little insect could carry aloft from two to two-and-a-half times its own weight—with ease. That means that, for their size, these creatures can lift three times more than the most efficient of man-made aircraft!
How do they do it? Luttges and his colleagues found that with each downstroke, the dragonfly twists its wing slightly, generating tiny whirlwinds on the top surface of the wing. This complex use of what engineers call unsteady airflows is a far cry from the way man-made airplanes fly; they depend on steady airflows. But it is the dragonfly’s ability to “tap the power of the whirlwind,” as National Wildlife puts it, that creates such “phenomenal lift.” Both the U.S. Air Force and the U.S. Navy are funding and supporting Luttges’ work. If airplanes could incorporate similar principles, they could take off much more easily and land on much smaller airstrips.
Matching the dragonfly’s maneuverability, though, would be another challenge altogether. National Wildlife notes that from the time the dragonfly takes its very first flight, it performs “immediately the miracles that today’s most sophisticated human aviators can only envy.”
Little wonder, then, that paleontologist Wootton concluded on this subject: “The better we understand the functioning of insect wings, the more subtle and beautiful their designs appear.” He added: “They have few if any technological parallels—yet.”
“Yet.” That one word reveals the optimistic—if not arrogant—human belief that given enough time, man could duplicate virtually any of the Creator’s works. No doubt man will continue to produce remarkable, ingenious imitations of what he finds in nature. But we should bear one point in mind. It is one thing to imitate; it is quite another to originate. As the wise man Job said over 30 centuries ago: “Ask, please, the domestic animals, and they will instruct you; also the winged creatures of the heavens, and they will tell you. Who among all these does not well know that the hand of Jehovah itself has done this?”—Job 12:7, 9.