Abstract: 【Aim】 In the biological control of Myzus persicae, Aphidius gifuensis is widely used in production practice due to its significant parasitic advantages. However, in the process of large-scale breeding of this parasitoid wasp species, after many generations of breeding, the parasitization ability is weakened and the body size becomes smaller. This study aims to clarify the physiological and biochemical degradation mechanism of the parasitization ability of A. gifuensis by measuring and analyzing the changes in parasitization ability on M. persicae and contents and activities of growth and development-related enzymes of A. gifuensis reared in laboratory for 12 generations. 【Methods】 A. gifuensis collected in the field was randomly selected, and reared for five generations (1st, 3rd, 6th, 9th and 12th generations) in groups indoors. The parasitization ability ［parasitism rate and body size (hind tibia length)］, and the contents and activities of growth and development-related enzymes including carboxylesterase (CarE), phenoloxidase (PO), superoxide dismutase (SOD) and trehalase in A. gifuensis adults of different generations were measured. 【Results】 The parasitism rate and hind tibia length of adult offspring of A. gifuensis were significantly affected by the indoor-rearing generations. The parasitism rate and hind tibia length of the F₁₂ generation of A. gifuensis adults were decreased by 36.70% and 38.54%, respectively, as compared to those in the F₁ generation. Indoor-rearing generations significantly affected the contents of growth and development-related enzymes in adults of A. gifuensis offspring. The contents of CarE, PO, SOD and trehalase in adults of the F₁₂ generation of A. gifuensis were decreased by 54.00%, 43.13%, 35.82% and 45.87%, respectively, meanwhile the activities of PO and SOD in adults of the F₁₂ generation of A. gifuensis showed no significant change, as compared to those in the F₁ generation. Additionally, the contents of CarE, PO, SOD and trehalase in adult offspring of A. gifuensis were significantly positively correlated with the parasitism rate, the CarE content and CarE activity in adult offspring of A. gifuensis were also significantly positively correlated with the hind tibia length of A. gifuensis. 【Conclusion】 With the increase of indoor-rearing generations, the parasitism rate and the body size of the adult offspring of A. gifuensis generally decline, and the contents of the growth and development-related enzymes and CarE activity in the adult offspring of A. gifuensis exhibit significant change.

Key words: Aphidius gifuensis, Myzus persicae, parasitization ability, protein content, enzyme activity, artificial propagation