In biology, moulting (or molting, ["Molting" vs. "moulting" -- see spelling differences.] also known as shedding or for some species, ecdysis) signifies the manner in which an animal routinely casts off a part of its body (often but not always an outer layer or covering), either at specific times of year, or at specific points in its life-cycle.
Moulting can involve the epidermis (skin), pelage (hair, fur, wool), or other external layer. In some species, other body parts may be shed, for example, wings in some insects. Examples include old feathers in birds, old hairs in mammals (especially dogs and other canidae), old skin in reptiles, and the entire exoskeleton in arthropods.
Examples
"See Go Pets for Ref"[ [http://www.gopetsamerica.com/dogs/dogs-that-do-not-shed.aspx Go Pets America: Dogs that do not shed - Retrieved September 7, 2008] ] ]Reptiles
The most familiar example of moulting in reptiles is when snakes "shed their skin". This is usually achieved by the snake rubbing its head against a hard object, such as a rock (or between two rocks) or piece of wood, causing the already stretched skin to split. At this point, the snake continues to rub its skin on objects, causing the end nearest the head to peel back on itself, until the snake is able to crawl out of its skin, effectively turning the moulted skin inside-out. This is similar to how you might remove a sock from your foot by grabbing the open end and pulling it over itself. The snake's skin is often left in one piece after the moulting process. Conversely, lizards' skins fall off in pieces.
Arthropods
In arthropods, such as insects, arachnids and crustaceans, moulting is the shedding of the exoskeleton (which is often called its shell), typically to let the organism grow. This process is called ecdysis. Ecdysis is necessary because the exoskeleton is rigid and cannot grow like skin. The new exoskeleton is initially soft but hardens after the moulting of the old exoskeleton. The old exoskeleton is referred to as an "exuvium" (or exuvia).
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