The hindlegs of grasshoppers and locusts store energy in chitonous apodemes (muscle attachment sites) in order to amplify jumping power.
"And that's where energy storage comes in. Down to the size of a trout or a squid tentacle, unaided muscle can do a decent job with nothing more than ordinary leverage. Below that, muscle needs help; in practice, energy is put in slowly and stored elastically. Some kind of trigger then releases it at a higher rate. Work and energy may be conserved, but power gets amplified…A locust or grasshopper jumping with its hindlegs stores up work in chitinous apodemes and gets a tenfold power amplification (Bennet-Clark 1975)…Each of these creatures has some kind of a mechanical catch to prevent premature extension while the work is being put in; the specific arrangements, though, are different for each case." (Vogel 2003:476)
Learn more about this functional adaptation.