Abstract: 【Aim】 Imidacloprid is one of the widely used neonicotinoid insecticides. Studies indicated that sublethal doses of imidacloprid affect the larval development of honeybees and the foraging and learning behaviors of adult honeybees. This study aims to investigate the effects of sublethal doses of imidacloprid on the expression of immune and detoxification related genes and the activities of immune and detoxification related enzymes in house bees (1 day-old adults) and field bees (21 day-old adults) of Apis mellifera ligustica, so as to provide a scientific basis for the maintenance of honeybee health. 【Methods】 The 1 and 21 day-old adults of A. m. ligustica were fed with 50% (w/v) sucrose solution containing 0.1 ng/μL of imidacloprid ad libitum, the survival rates at different time after treatment were determined. The expression levels of PPOA3 (GenBank accession no.: GB43738), CYP450 6a2 (GenBank accession no.: GB49876), ABA (GenBank accession no.: GB18323), GLD (GenBank accession no.: GB43007) in the adult bees at 6 d after treatment were detected by real-time quantitative PCR, and the content of cytochrome P450 (CYP450) and the activity of polyphenol oxidase (PPO) in them were determined by double antibody one-step sandwich enzyme-linked immunosorbent assay. 【Results】 After the 1 day-old and 21 day-old adult bees of A. m. ligustica were continuously fed with 50% sucrose solution containing 0.1 ng/μL imidacloprid for 6 d, their survival rates showed no significant difference from the control ［fed with 50% (w/v) sucrose containing 0.1 ng/μL of acetone］ (P>0.05). After the 1 and 21 dayold adult bees of A. m. ligustica were continuously fed with 50% sucrose solution containing 0.1 ng/μL imidacloprid for 9 d, the survival rate of the 1 day-old adult bees showed no significant difference from the control, while the survival rate of the 21 day-old adult bees showed significant difference from the control. The expression levels of PPOA3, CYP450 6a2, ABA and GLD, the CYP450 content and the PPO activity in 1 day-old adult bees exposed to 0.1 ng/μL imidacloprid for 6 d were significantly downregulated as compared to those in the control. The expression levels of CYP450 6a2, ABA, and GLD and the PPO activity in 21 day-old adult bees exposed to 0.1 ng/μL imidacloprid for 6 d were significantly downregulated, while the expression levels of PPOA3 and the CYP450 content were significantly elevated as compared to those in the control group. 【Conclusion】 Sublethal doses of imidacloprid affect the expression of immune and detoxification related genes and the activities of immune and detoxification related enzymes in both house and field bees of A. m. ligustica. The short-term stress of imidacloprid has no significant effect on the survival of the house and field bees of A. m. ligustica, but long-term stress may affect their survival.

Key words: Apis mellifera ligustica, imidacloprid, immune, detoxification enzyme, survival rate, enzyme activity