The Exoskeleton is made up of a number of substances and is actually lighter than bone but is thought to be much stronger, serving as a protective suit for the internal organs of insects. Insects muscles are attached to the wall of the exoskeleton.
The skeleton does not grow with the body and there comes a time when the insect is too big for the exoskeleton and it is shed through a process known as moulting. A new exoskeleton is formed underneath the old one before the insect crawls out of the old one. The moulting process happens several times until the insect reaches the adult stage.