Chitin: A secrete ingredient for success?
Insects may cover this chitin with sclerotin to make it hard so as to create armour (e.g. beetles) and produce mouthparts sharp and tough enough to gnaw wood and cut metals. It is the responsiveness of this chitinous exoskeleton to evolutionary change that has permitted insects to diversify. Leg morphology is easily modified to propel an animal for more than two-hundred times its own length, or to create broad oars to row across the water or thin hair tipped stilts to stride across the surface of water. Many limbs may carry special tools moulded from chitin such as pouches to hold pollen, combs to clean compound eyes, spikes to act as grappling irons and notches to create sounds.