Some species of flea can jump up to 200 times their own body length. The mighty leap of this tiny, wingless insect is far too explosive to be powered by muscles alone. Instead, fleas harness energy stored in two blocks of resilin – a rubbery, spring-like protein – contained in the thorax.
The mechanism works by locking the back legs in a folded position and contracting large thoracic muscles to compress the resilin. Releasing the leg-lock then allows the blocks to recoil, extending the limbs in a fraction of a second.
In flying insects, resilin serves to bounce the wings back at the end of each stroke. The flea’s technique is an elegant example of evolution finding novel and ingenious uses for existing structures.