Epicuticle

The epicuticle is the outermost portion of the exoskeleton of an insect (and various other arthropods); its exact composition and structure may differ somewhat among different taxa, but certain aspects can be generalized:
* It is secreted by the epidermis, and is deposited on top of the procuticle via pores that pass outwards through the procuticle from the epidermal cells.
* It contains no chitin, and is itself arranged in layers.
* The layers typically consist of an inner epicuticle, an outer epicuticle (or cuticulin layer), a wax layer, and a cement layer.
* The wax layer is not present in all arthropods, as its primary function is to reduce water loss.
* The epicuticle cannot be digested during the molting cycle (see ecdysis), so it and the exocuticle are shed.