The secret lives of fleas

Researchers at the University of Cambridge in England revealed the mechanics of a flea’s jump—which can catapult the critter 50 to 100 times its body length. Fleas jump because of an elastic pad made of a protein called resilin. When tensed like a spring, fleas release the pad to catapult themselves into the air. However, researchers wanted to know how fleas achieve liftoff and transfer the force from the spring mechanism to the ground. Cambridge researchers discovered the answer by using high-speed cameras, computer modeling, and 10 donated hedgehog fleas.

Using the cameras, researchers filmed the fleas jumping 51 times in a row. During 45 of those jumps, the fleas’ feet and knees were on the ground when the flea pushed off. However, in the remaining six jumps, the knees were both clear of the ground at that time, indicating they didn’t transfer the force of the jump to the ground. In all of the jumps the feet touched the ground, supporting a lower-leg push-off theory.