Chitin (C8H13O5N)n 's a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and's found in many places throughout the natural world. It's the main component of the cell walls of fungi, the exoskeletons of arthropods, such as crustaceans (for example crabs, lobsters and shrimps) and insects, including ants, beetles and butterflies, the radula of mollusks and the beaks of cephalopods, including squid and octopuses. Chitin has also proven useful for several medical and industrial… (More on Chitin)