none Further investigations have been made to explore the interaction between the pathogen Bacillus thuringiensis and the parasites and predators associated with the cotton leafworm Spodoptera littoralis . The biology of the parasite Zele chlorophthalma showed to be affected when its host larvae (S. littoralis ) were fed on a diet containing B. thuringiensis var. entomocidus . A significant reduction in the percentage of parasitism, parasite emergence and reproductive potential was observed as a result of treatment of host larvae with the pathogen. Also, a retardation in development occurred. In the predator Paederus alferii , however, no effects were observed after feeding the adults on S. littoralis larvae treated with the pathogen. It seems that the parasites of cotton pests are more affected than the predators when they were allowed to feed on hosts larvae contaminated with B. thuringiensis .