Chitin

A structural carbohydrate that forms the exoskeleton of many insects and crustaceans. What makes bugs crunchy. Yum.

Chitin can be compared to cellulose in plants and glycogen in animals in that they are all carbohydrates that are used for structural purposes.

And what Webster said. It's white and, um....horny. (tee hee!)

It is secreted in the ectoderm and commonly forms the exoskeleton of invertebrates. It is a material much like collagen, which forms the connective tissue of many advanced animals, but collagen is secreted in the mesoderm.

In the exoskeletons of invertebrates chitin is one component of a protein - chitin complex. Chitin may be decomposed by bacteria and digested by enzymes but, if buried, may persist for hundreds of millions of years and is known from rocks as old as Cambrian in age.

Chi"tin (?), n. [See Chiton.] Chem.

A white amorphous horny substance forming the harder part of the outer integument of insects, crustacea, and various other invertebrates; entomolin.

© Webster 1913.