The photoperiodic regimes [24L, 13L 11D (natural condition), 18L6D, 12L12D, 6L18D and 24D] played a vital role on nucleic acid, protein content of fat body and larval-pupal characters of silkworm, Bombyx mori. Prolonged larval duration with a significant increase in weight of the larvae, silkgland, cocoon, pupa and shell was noted in the larvae exposed to 24L period. A significant positive correlation (r = 0.97, P < 0.01) between larval weight and egg production was noted. The DNA, RNA and protein contents increased at 24L over that of 13L11D group as well as other photicregimes.
