Insects and their arthropod relatives—shrimp, crabs, and lobsters—possess exoskeletons, a combination skin and skeleton which protects them against crushing, scratching, invasion by microorganisms, and water loss. A hard, durable exoskeleton is a great protective device, but it is a real problem as the insect grows—it wont' stretch.
Knights of olde who covered themselves with suits of armor had a similar problem at times. Indeed, the knight who forgot to mind his waistline discovered the need for a new suit. Insects face a similar problem several times during their life cycles, and like the ancient knights, they acquire new suits of armor.
Before an insect grows a new exoskeleton, it sheds the old one, a process called molting. Most people are familiar with the shed skins of insects. Or instance, what youngster hasn't gathered the conspicuous shells of cicadas? When the immature cicada nymph emerges from its underground home, it immediately molts to the winged adult stage. The old exoskeleton can be fond fastened to a tree, shrub, or fence post. Aphids also molt, and sometimes the only evidence of these pest insects on a plan will be hundreds of white ghost-like skins.
Insect molting has long fascinated scientists, who have worked hard to describe the chemical nature of the process. Even poets have noticed – and described—the magic of an insect shedding its skin. In Tennyson's “The Two Voices,” we read about a dragonfly molting:
‘An inner impulse rent the veil
Of his old husk; from head to tail
Came out clear plates of sapphire mail.'
The ancient Greeks were aware of the molting process and had a word to describe it—ecdysis (eck DEE sis). It was from this word that H.L. Mencken coined his humorous term for a stripteaser—an ecdysiast!
The practical nature of an insect molting might not hold the same attraction to most people as the dance of a stripteaser. However, the result is the same; both the insect and the ecdysiast end up removing their outer clothing.