Field foliar residues of five modern insecticides viz, Emamectin benzoate, Indoxicarb, Spinosad, Flubendiamide and Bacillus thurngiensis in tomato plants, have been evaluated by feeding larvae of the Lepidopteran Spodoptera littoralis (Boisaduval, 1833). Laboratory conditions were selected to study the long-term effects of feeding larvae on the growth and development of S. littoralis throughout its life cycle. Residues Spinosad exhibited the highest mortality 87.7 and 83.6%, against 2nd and 4th instars larvae respectively, followed by Flubendiamideand B. thurngiensis while residues Emamectin benzoate and Indoxicarbshowed the significantly lowest mortality. On the contrary, Emamectin benzoate showed the highest initial kill against 2nd and/or 4th instars larvae, while Spinosad longest residual effect among the tested insecticides. The increased larval duration was observed before pupation with the slowed metamorphosis from larvae to pupae. Treated larvae exhibited lower pupal weights, higher pupal mortality, presence of deformed pupae, and more deformed adults than untreated larvae. All insecticides had a significant effect on the timing of larval development and adult longevity. The development period for males and females was about four days lower than the control for all insecticides tested. Finally, S. littoralis adults that resulted from second and fourth instars treated with tested insecticides were affected in their mean cumulative number of eggs laid per female (fecundity), significantly (P=0.05) decreased egg fertility, and the sex ratio. Our results suggest that the residues of modern insecticides may have important implications for the population dynamics of the cotton leafworm.