Cytochemical changes in the silk gland cells ofPericallia ricini (Lepidoptera: Arctiidae)

Abstract

Cytochemical changes involving PAS -positive and metachromatic substances have been studied in the silk gland cells of the moth Pericallia ricini during growth and atrophy. The distinction between the silk-periphery and silk-core on the basisof metachromatic staining has been traced even in the second instar stage for the first time. PAS-reaction differentiates the same in the prepupal stage. The secretion of two silk constituents goes on simultaneously in the gland cells. The conjugation of PAS-positive polysaccharide group to silk protein takes place in the apical cytoplasm of the gland cells. The core silk secretion predominates in the prepupal stage. Reduction in the amount of carbohydrate material in the basal cytoplasm of the silk gland cells from first instar to prepupal stage occurs with their simultaneous concentration in the apical region of the cells. The degree of metachromasia increases progressively in advancing instars.