Support, Protection and Movement

An ant carries with ease a flower petal that is heavier than the ant’s body weight

Of Grasshoppers and Superman
“A dog,” remarked Galileo in the seventeenth century, “could probably carry two or three such dogs upon his back; but I believe that a horse could not carry even one of its own size.” Galileo was referring to the principle of scaling, a procedure that allows us to understand the consequences of changing body size. A grasshopper can jump to a height of 50 times the length of its body, yet a man in a standing jump cannot clear an obstacle that is no higher than he is tall. Without an understanding of scaling, this comparison could easily lead us to the erroneous conclusion that there is something very special about the musculatures of insects. To the authors of a nineteenth-century entomology text it seemed that “This wonderful strength of insects is doubtless the result of something peculiar in the structure and arrangement of their muscles, and principally their extraordinary power of contraction.” But grasshopper muscles are in fact no more powerful than human muscles because muscles of small and large animals exert the same force per cross-sectional area. Grasshoppers leap high in proportion to their size because they are small, not because they possess extraordinary muscles.

The authors of this nineteenth-century text further suggested that it was fortunate that higher animals were withheld the powers of insects, for they would surely have “caused the early desolation of the world.” More probably, such powers would have led to their own desolation. For earthly mortals would need more than superhuman muscles were they to leap in the proportions of a grasshopper. They would require superhuman tendons, superhuman ligaments, and superhuman bones to withstand the stresses of mighty contractions, not to mention the crushing strains of landing again on earth at terminal velocity. The feats of Superman would be quite impossible were he built of the structural materials available to earthbound animals, rather than of the wondrous materials available to inhabitants of the mythical planet Krypton.