Science: The Grasshopper's Hop

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To a zoologist, the leap of the grasshopper is one of the wonders of the world. An adult grasshopper can leap ten times its length in the high jump, 20 times its length in the broad jump. A man up to a grasshopper's hop-to-length standards could clear a five-story building, or bound the length of a football field in three jumps.*

Besides the fascination of these athletic feats, the grasshopper gives the zoologist other good reasons for study. Plagues of locusts (shorthorn grasshoppers) can still endanger the food supply of millions. Knowledge of the nervous system that fires the grasshopper's jumping muscles may lead to an effective insecticide.

For science and the sheer fun of it, Zoologist Graham Hoyle of the University of Glasgow set about learning what puts the hop in the grasshopper. Writing in Scientific American, Hoyle tells how he used a slow-motion camera to analyze how the insect cocks its rear legs "by squatting with the femurs (thighs) doubled against the tibiae (shins)," rears up and takes off with a velocity of about 10 ft. per second. The jumping muscle of the grasshopper, which weighs only one twenty-fifth of a gram, develops "the astounding power of some 20,000 grams per gram of its own weight," or ten times the power of human muscles working at top speed. Says Hoyle: "The only known muscles in the whole animal world that equal this power are the shell-closing muscles of the clam—but the grasshopper's muscles work far more rapidly."

Even more astonishing is the grasshopper's nervous system, which can fire his leg muscles at either a stroller's gait or a flat-out leap. Hoyle says the control lies in two simple nerve fibers that attach to the jumping muscles; one is for slow action, one for leaping. The tiny bundles of muscle fibers that are packed like the fibrils of a feather all along the thigh are never fully activated by impulses carried by the slow-action circuit, and so the grasshopper can walk where it pleases.

But when it is hopping mad, the grasshopper sends down a nervous impulse that "inhibits the slow nerve fiber and puts it out of action." All further impulses go on the fast-action fiber. How far the grasshopper leaps depends on the number of impulses it sends its leg muscles: one impulse produces a hop; two a "moderate jump"; three an all-out effort. Somehow the grasshopper gets all this done in one-thirtieth of a second. Marvels Grasshopperman Hoyle: "A superb example of natural economy."

*Russian Yuri Stepanov (6 ft. 1 in.) holds the unofficial world high-jump record of 7 ft. 1 in.; American Jesse Owens (5 ft. 111n.) holds the running broad-jump record of 26 ft. 8 in.