الفهرس 
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Abstract
The present study was conducted to evaluate the effect of gamma irradiation on certain biological aspects of the cotton leaf worm Spodoptera littoralis (Boisd.). Laboratory experiments were carried out to investigate the effect of the substerilizing doses of 0, 50, 150, 250, 350 and 450 Gy of gamma irradiation (cobalt and cesium sources) on different generations of Spodoptera littoralis irradiated as pupae to study the inherited sterility. A dose level at 450 Gy completely inhibited full pupal development, but the emerged adult at the dose 350 Gy did not lay eggs, whether they were combined with non-irradiated or irradiated individuals of opposite sexes.
The produced adults (P) showed increasing sterility with increasing the irradiation dose. While, their fertility, fecundity, pupation percent and adult emergence were found to be reduced in the parents followed by F1, but increased in F2. In all cases, sex ratio was shifted in favor of males.
A significant negative relationship between dose levels and percentage of egg hatching was obtained; [the higher the dose, the lower the percentage of egg hatching]. The percentage of egg hatching resulting from irradiated male pupae was higher than that resulting from irradiated female pupae. Females were more sensitive for irradiation than males.