The Jumping Ability of the Common Flea
Fleas, the annoying parasites that are the bane of dogs' existence are very interesting creatures. They are tiny and have no wings but amazingly have no problems climbing onto the backs of creatures and sometimes on people's heads. This is because of their long hind legs that make the flea perfectly suited for jumping. They can jump 13 inches horizontally, which is 200 times their body length! That is like a human jumping nearly a quarter mile in a single leap. A new study published in the Journal of Experimental Biology unlocks the secret of the flea's amazing jumping ability.
The research was conducted by Malcolm Burrows and Gregory Sutton. They had heard all previous theories as to how fleas jump. However, none were conclusive because the high speed recording technology required to prove them did not exist. So the two went about to settle the debate by filming jumping fleas. They successfully filmed 51 jumps from ten different fleas. "We were concerned about how difficult it would be to make the movies because we are used to filming locusts, which are much bigger than fleas," admits Sutton, but he and Burrows realized that the fleas stayed perfectly still in the dark and only jumped when the lights went on.
They found that the jumping power came from the flea's toes and not the knees, as was formerly suspected. In most jumps, both the toe and knee were in contact with the ground for pushing off, but in ten percent, only the toes touched the ground. This suggested that either the knee was not really necessary or both mechanisms were used to get airborne.
After analyzing the flea's leg with an electron microscope, they noticed that there were gripping claws and hairs on the toe and shin, but not on the knee. To clinch their argument that the toes did the jumping, the researchers employed a mathematical model that could reproduce the flea's trajectory. One model using the knees to jump, and one using the toes.
Both models predicted the same speed at take-off of 1.35 meters per second. However, the "knee model" did not match up with reality. It predicted a top rate of acceleration of 22,000 meters per second squared, when the reality is only 1,500 meters per second squared.
The argument is now considered settled. Fleas transmit the force of their jumps from a spring in the thorax through the leg, acting on a lever to push down the toes and catapult the tiny creatures.
Link to published article: http://jeb.biologists.org/cgi/content/short/214/5/i