UTTAR PRADESH JOURNAL OF ZOOLOGY

The rice moth, Corcyra cephalonica (Stainton), is a major stored-product pest and a widely used factitious host in biological control programmes. Accurate identification of larval instars is important for studies on developmental biology and for stage-specific rearing and management strategies. This study determined the larval instars of C. cephalonica using morphometric parameters on two sesame genotypes, Swetha and GT-10, under laboratory conditions. Head capsule width, body length, body width and developmental duration were recorded across larval stages, and the conformity of growth patterns with Dyar’s rule and Przibram and Megušar’s growth law was assessed. The results showed that C. cephalonica completed five larval instars on both genotypes. Head capsule width increased progressively with successive instars and showed a clear linear relationship with larval development, supporting the applicability of Dyar’s rule. By contrast, body length and body width did not follow the geometric progression proposed by Przibram and Megušar’s rule, indicating that these measurements were less reliable for precise instar separation. Differences in morphometric values and developmental duration between Swetha and GT-10 indicated that host genotype influenced larval growth and development. Overall, head capsule width was the most dependable morphometric character for determining larval instars of C. cephalonica on sesame genotypes.