One small step for science, one giant leap for fleakind

IT WAS a theory created by an Edinburgh University academic in 1967 but challenged by a rival researcher.

Now Dr Henry Bennet-Clark's explanation of how a flea can jump up to 200 times its own body length has finally been proved by scientists in Cambridge.

Malcolm Burrows, of Cambridge University's Zoology department, ended more than 40 years of debate by proving that fleas actually use their toes to propel themselves into the air.

Dr Bennet-Clark's original discovery, that the insects store the energy needed to catapult themselves into the air in an elastic pad in a leg joint, could not be proved because the technology to record it was not available.

And a rival idea, put forward five years later by flea expert Dame Miriam Rothschild, claimed the creatures needed to lie their trochanters - the lower parts of their legs - flat against the ground in order to create enough momentum to leap.

But it was when Mr Burrows was last year asked to write a paper for the Journal of Experimental Biology in celebration of Dr Bennet-Clark's original work - carried out with the late Eric Lucey while he was a lecturer at Edinburgh University - that he realised further research had never been done.

"I looked at Henry's original paper and saw that no-one had ever taken it further in 40 years to resolve it," said Mr Burrows.

He then teamed up with biomechanics expert Greg Sutton and collected fleas from rescue animals at St Tiggywinkles Wildlife Hospital, Buckinghamshire.

"We decided we would get hold of some fleas and took it from there," he said. The pair then used high-speed recording equipment to follow the movements of ten fleas, taking a total of 51 leaps.

In the majority of the jumps, which launch at nearly two metres a second, both parts of the flea's leg - the tarsus (tiny spines equivalent to the toe) and the trochanter - were in contact with the ground as the flea pushed itself off, but in 10 per cent of the jumps only the toe was in contact with the ground.

"It looked to us like the tiny joints were touching the ground as the feet would be in a human - but the knee joint was not always on the ground," Mr Burrows added. Dr Bennet-Clark, now Emeritus Fellow at St Catherine's College, Oxford, said he was happy his theory had been proven.

"I'm not so much excited about it as just saying 'Good - that merely confirms it'," he said.

"In 1967 I did effectively say that they must jump in that way.

"The suggestion Miriam Rothschild made - that they might jump off their trochanters - is about as silly a suggestion as saying you could jump out of a chair by clenching your buttocks."

He added: "In a sense, it is no surprise to me, but it is nice to have it confirmed."