The cuticle of the cockroach Periplaneta americana . III. The hardening of the cuticle: impregnation preparatory to phenolic tanning

Abstract

The changing properties of the outer layers of the cuticle of Periplaneta during preparation for phenolic tanning are due to the passage into them, by different routes, of a lipoid and a protein. Both inner and outer zones of the pre-exuvial endocuticle become impregnated, but the final concentration of the lipoprotein mixture is much greater in the outer zone than in the inner. The lipoid is a sterol which imparts a yellow colour to the cuticle, and the protein is rich in phenolic groups owing to the presence of tyrosine. The isoelectric point of the protein is similar to that of tyrosine.