Two biopesticides Serratia marcescens [Eubacteriales: Enterobacteria] (used at MC₅₀, concentration caused 50% malformation) and Bacillus thuringiensis Var. kurstaki (used at LC₅₀) and insect growth regulator Teflubenzuron (used at LC ₅₀ value) were used for treatment of 2^nd instar larvae of cotton leafworm, Spodoptera littoralis (Boisd.). Sequential combined Effect was carried out bytreating 2^nd instar larvae with LC₅₀   value of B. thuringiensis or Teflubenzuron then the larvae allowed to pupate on sawdust treated with S. marcescens at MC₅₀  .The effect of these three agents were assessed by toxicity The obtained LC₅₀ valueswere 0.113 and 165.64 ppm, for Teflubenzuron and B. thuringiensis Var. kurstaki. (protecto), respectively. Moreover, the activity of Chitinase, protease, trehalase, and the main components (total lipids, proteins and carbohydrates) were significantly fluctuated during the different periods of pupal stage.