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Injection of heat killed Escherichia coli into the 5th instar of Schitocerca gregaria lead to deleterious effect on macromolecules such as proteins, lipids, and DNA, which expressed in the form of increased levels of carbonyls, peroxides, strand breaks, respectively. The results showed significant difference, in macromolecules damage, between control insect and injected one through time course and application of different concentration of E. coli. The present results were focusing on properties of lipopolysaccaride of bacterial cell wall which cause production of nitric oxide radical as an immune response of insect and also can react with superoxide anion radical that form peroxynitrite that considered as reactive nitrogen species which cause macromolecules damage Also, the results showed that the antioxidant enzymes activities, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) were elevated over constitutive levels, in response to the injected oxidative stressor heat killed E. coli. The levels of both the constitutive and induced activities of GPx and are always higher in whole midgut homogenate than in thoracic muscles. The results may represent some sort of stressful conditions that may increase the vulnerability of insect pests to control measures.