Quantitative histochemical measurements of activities of enzymes were performed by temporal defined stages in development of Protophormia terraenovae. The effect of the specific insecticide of moult Duphar pH 60-38 activity of enzyme was evaluated. Activities of peroxidase and tyrosinase showed parallel oscillations, at which proof of both enzymes was restricted to the cuticle. The insects, treated with insecticide, showed a moulting, dependent on concentration. A transfer of maxima of activities is described.