An animal behaviourist, professor for flea jumping, is studying a flea. He has it on a lab bench, and calls "HEP!". The flea jumps and the professor measures the distance, 60 cm, remakarble for such a small animal.

The professor uses a pair of fine tweezers to pull of two of the flea's legs. Again, he calls "HEP!" and the flea jumps, this time 40 cm.

Again the professor removes two legs, calls "HEP!" and the flea jumps, now only 20 cm.

Now the professor pulls off the last two legs, calls out "HEP!". The flea doesn't move.

The professor writes into his note book, "A flea with all legs removed loses its hearing".