If you thought that we know everything about how the flea jumps, think again. In 1967, Henry Bennet-Clark discovered that fleas store the energy needed to catapult themselves into the air in an elastic pad made of resilin. However, in the intervening years debate raged about exactly how fleas harness this explosive energy. Bennet-Clark and Miriam Rothschild came up with competing hypotheses, but neither had access to the high speed recording equipment that could resolve the problem. Turn the clock forward to Malcolm Burrows' Cambridge lab in 2010. 'We were always very puzzled by this debate because we'd read the papers and both Henry and Miriam put a lot of evidence for their hypotheses in place and their data were consistent with each other but we couldn't understand why the debate hadn't been settled,' says Burrows' postdoc, Gregory Sutton. He adds, 'We had a serendipitous set of hedgehog fleas show up so we figured we'd take a crack at it and try to answer the question'. Filming leaping fleas with a high-speed camera, Sutton and Burrows found that fleas push off with their toes (tarsus) and publish their discovery in The Journal of Experimental Biology at http://jeb.biologists.org/cgi/content/abstract/214/5/836.
'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 realised that the fleas stayed perfectly still in the dark and only jumped when the lights went on. Focusing the camera on the stationary insects in low light, the duo successfully filmed 51 jumps from 10 animals; and this was when they got their first clue as to how the insects jump.
In the majority of the jumps, two parts of the flea's complicated leg the tarsus (toe) and trochanter (knee) were in contact with the ground for the push off, but in 10% of the jumps, only the
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The Company of Biologists