Experiments were carried out in Bollworms Research Department, Plant Protection Research Institute, Sharkia Branch to study effect of light (14L : 10Dh) and dark (24 Dh) on the biological and physiological aspects of Helicoverpa armigera (Hubner). The obtained results showed that, at the biological aspects, the larvae and pupae of H. armigera reared under light condition gave higher weights compared with those reared under dark condition. Under light the larval and pupal duration were shortened and larval & pupal mortality percentages were lowest. The highest adult emergence percentage, average number of deposited eggs/female and hatchability percentages were recorded for that reared in light condition compared with those reared in dark condition. At physiological aspects, H. armigera reared under light condition, its contents of total soluble protein and carbohydrate was increased and decreased of total lipid compared with those reared under dark condition. The results indicated that the increasing in the total contents of protein and carbohydrates in the larvae reared under light condition will be lead to increase the number of eggs/female and hatchability percentage.