The exoskeleton or integument of insects acts as an impermeable, protective layer against desiccation. It is composed of an outer epicuticle, underlain by a procuticle that itself may be further divided into an exo- and endocuticle. The endocuticle provides the insect with toughness and flexibility and the hard exocuticle serves to protect vulnerable body parts. However, the outer cuticular layer (epicuticle) is a protein-polyphenol complex made up of lipoproteins, fatty acids, and waxy molecules, and is the insect's primary defense against water loss. Many insect orders secrete an additional cement layer over their wax layer, likely to protect against the abrasion or removal of waxy molecules. This layer is composed of lipids and proteins held together by polyphenolic compounds and is secreted by the dermal glands.
