The tanning of insect cuticle—A critical review and a revised mechanism

Two mechanisms to account for the stiffening of cuticle at tanning were proposed in 1940. The quinone tanning theory has been almost universally accepted; that of dehydration almost universally neglected. Calculations and tests on the mechanical properties of cuticle under differing conditions suggest that covalent cross-linking, even if it exists, is insufficient to account for the degree of stiffening of cuticle at sclerotisation. Dehydration will induce sufficient secondary bonds to account for the stiffness and insolubility of ‘tanned’ cuticle in the complete absence of covalent cross-links. It is suggested that the mechanism of sclerotisation is driven by quinones and other chemicals which are secreted into the cuticle at sclerotisation and cause highly controlled dehydration. Covalent cross-linking may still occur, but must be considered to be of secondary importance and unproven in all cuticles other than resilin.