The effectiveness of some essential oils -menthol, lemon and their mixture was evaluated under laboratory conditions against egg masses, 2nd instars larvae and pupae of cotton leaf worm, Spodoptera littoralis.. The obtained results indicated that the effect of the oils on S. littoralis eggs can be summarized as delayed embryonic development and ovicidal activity. According to the hatchability % of the treated eggs, data showed that at the lowest concentration (5000 ppm), of the mixture (35.8 ± 6.1%) , lemon (41.7 ± 4.7 % ) and  menthol extracts (45.8  ± 7.8 %) caused a significant reduction in percent hatchability compared with control (90.3 ± 6.2 %).   On the other hand  ,mixture of menthol and lemon oils exhibited the highest toxic effect against egg stage followed by lemon and menthol extracts. However, the LC50 values were 456.09, 2130.13 and 3456.17 ppm, respectively. The oils showed toxic and morphogenetic effects on S. littoralis 2^nd instars larvae. Mixture of menthol and lemon was the most effective against 2^nd instars larvae of S.littoralis followed by lemon and menthol alone. The LC₅₀ values were 6813.79, 11410.92 and 11944.89 ppm, respectively. On the other hand, the extracted oils had been shown to cause some morphological changes in treated larvae. In respect to pupal stage, menthol caused the highest toxic effect against S.littoralis pupae followed by the mixture and lemon extract .on the other hand, all extracted oils caused malformations in the emerged moths Effect of LC₅₀ of the plant extracts on 2nd instar larvae of S. littoralis was evaluated under semi-field conditions .Mixture was the most effective against S.littoralis larvae followed by lemon and menthol compounds. The LC₅₀ values were 6813.8, 11410.9 and 11944.9ppm, respectively.