Ecdysis is the moulting of the cuticle in many invertebrates. After moutling an athropod is described as ‘teneral’, ‘a callow’; fresh, pale, vulernable and soft bodied. During this short process the animal expands, since growth is otherwise constrained by the rigidity of the exoskeleton. This growth of the limbs is achieved by transfer of bodily fluids. Some athropods, especially large insects with trachael respiration, expand their new exoskeletons by swallowing or otherwise taking in air.

The term ecdysis comes from the ancient Greek ‘ekduo’ - to take off, strip away.