One moment, the 10 fleas were happily sucking blood from hedgehogs being treated at Tiggywinkles Wildlife Hospital in Aylesbury, which, of course, is in England.

The next, they were being plucked from their comfortable home and transported to Cambridge, where they ended up in a glass box with a Styrofoam floor. From time to time, bright lights would flood the box, so that a high-speed camera could film them. And the fleas did what fleas do in times of crisis: they jumped.

When fleas jump, it is no ordinary leap. The insects can shoot as high as 38 times their body length, about three inches. And the acceleration is so intense that fleas have to withstand 100 Gs, or 100 times the force of gravity. “You and I pass out if we experience five Gs,” said Malcolm Burrows, an expert on insect jumping at the University of Cambridge.

Dr. Burrows and his Cambridge colleague Gregory Sutton obtained the fleas from Tiggywinkles to try to answer a question that had vexed naturalists for centuries: how fleas manage their spectacular jumps. In a paper published Thursday in The Journal of Experimental Biology, they report that the insects turn themselves into catapults, storing up energy that they release as they push off the ground with what passes, in fleas, for feet.