If you've ever tried to catch a grasshopper, you know how far they can jump to flee danger. If humans could jump the way grasshoppers do, we would be able to easily leap the length of a football field. How do these insects jump so far? It's all in those big, back legs. A grasshopper's hind legs function like miniature catapults. In preparation for a jump, the grasshopper contracts its large flexor muscles slowly, bending its hind legs at the knee joint. A special piece of cuticle within the knee acts as a spring, storing up all the potential energy. The grasshopper then relaxes its leg muscles, allowing the spring to release its energy and fling the insect into the air.