Chitin

Chitin is a long-chained polymer and derivative of glucose often found as a component of the exoskeletons of many species. It is made up of carbon, hydrogen, oxygen and nitrogen.

Found Inside
Chitin makes up the exoskeletons of crustaceans, surrounding their claws and legs and making up their shell. It also makes up the exoskeleton of insects, and hence surrounds their legs, claws, stingers, antennae and wings.