Chitin is the main component in this supportive outer covering of lobsters & insects
It includes 
most of the material of the exoskeleton of the insects, Crustacea, ... To achieve 
such rigidity the outer chitin layer of the cuticle is impregnated, thickened, ... but 
also may form mechanical components of the exoskeleton, such as the in legs, 
joints,... [DOC] [TLE] chitin facts, information, pictures | Encyclopedia.com articles about ... [PAR] Chitin is a major constituent of the exoskeleton, or external skeleton, of many 
arthropods ... to cellulose, the compound that provides structural support to plant 
tissues.