The efficiency of three insect growth inhibitors (IGIs); namely: Lufenuron, Flufenoxuron and Chlorfluazuron against the cotton leafworm Spodoptera littoralis was studied. The least efficient minimized doses were determined for measuring their delayed effect on the fitness components and reproductivity of the insect-pest; throughout sex following generations. Chlorfluazuron achieved superior toxic efficacy overall the other tested IGIs. In some cases of used lower concentrations, bleeding took place in the newly moulted larvae. The used lower concentrations of Flufenoxuron caused a case of antifeeding effect due to paralysis of the musculature of larval mouth parts. The tested IGI's, slightly and insignificantly affected the durational periods of treated insect pest. The lowest measured weights of larvae, pupae; the least number of oviposited eggs and hatch percent was detected for the treatment of Flufenoxuron least minimized dose. The consequent treatment of the least efficient dose of each tested IGI to a more or less extent, reflected its drastic effect on the of developing stages. Besides the revealence of (F₁) female-moths possessing shortened atrophied ovarioles with undifferentiated oöcytes. The calculated values of sterility and induced dominated lethals (genes) reaced its extremity at the end of 2^nd generation in case of Flufenoxuron, the 6^th Lufenuron and the 5^th Chlorfluazuron causing the complete termination of the life cycle of the insect.