Abstract:  【Aim】 To understand the effect of the intestinal symbiotic bacteria Citrobacter freundi and Klebsiella oxytoca on the development and substance metabolism of the spotted wing drosophila, Drosophila suzukii. 【Methods】 The egg hatching rates, body weight of the 3rd instar larvae and pupation rates of the normal D. suzukii strain, sterile D. suzukii strain, C. freundi infected D. suzukii strain and K. oxytoca infected D. suzukii strain were determined. The contents of metabolites including protein, amino acids, glycogen and 
free fatty acids and the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the 3rd instar larvae of these D. suzukii strains were detected. 【Results】 The egg hatching rate, body weight of the 3rd instar larvae, pupation rate and 
protein content in the 3rd instar larvae of the normal D. suzukii strain were all higher than those of other strains, while those of the sterile D. suzukii strain were the lowest. The 3rd instar larvae of D. suzukii strains infected by C. freundi or K. oxytoca had lower 
contents of amino acids and glycogen than the sterile and normal D. suzukii strains. The contents of free fatty acids in the 3rd instar larvae of D. suzukii infected by C. freundi were also lower than those in the other D. suzukii strains. In the 3rd instar larvae of D. 
suzukii strains infected by C. freundi or K. oxytoca, the POD activity was significantly higher than those in the sterile and normal strains, while the CAT activity was significantly lower than those in the sterile strain. 【Conclusion】 The development of D. 
suzukii delays in the absence of intestinal symbiotic bacteria. However, the development of D. suzukii can be enhanced in some extent after adding C. freundi or K. oxytoca in the food, and this is closely related to the changes of metabolites in D. suzukii after adding 
intestinal bacteria.

Key words: Drosophila suzukii; Citrobacter freundi, Klebsiella oxytoca, intestinal bacteria, growth and development, metabolites, antioxidant enzymes