Typical development in mites begins with the retraction of the epidermis from the cuticle. It is accompanied by a decrease in size and a change in shape. Atypical development also begins with a moult. But it is distinguished by regrowth, a change in shape, and an extra moult.
Each moult is unique in that the epidermis divides into an outer and an inner layer. The outer layer adheres to the old cuticle. Its cells are provisionally regarded as being the source of the moulting enzymes. The inner layer retracts and persists as the true epidermis.
The components of mite cuticle, according to histochemical tests, resemble those of insect cuticle.
The formation of a provisional cuticle during atypical development produces the condition generally recognized as a pupal state. The moult of this provisional cuticle is primarily aimed towards synchronizing cuticle deposition with muscle development. Integration of the intermediary connecting processes, the fibrillae, with both the muscle ends and the cuticle is thus made possible.