Abstract: 【Aim】To explore the response mechanism of antioxidant and detoxification enzyme activities in Holotrichia oblita, H. parallela and Anomala corpulenta following pathogen infection. 【Methods】The 2nd instar larvae of H. oblita, H. parallela and A. corpulenta were infected by the spore suspension of Beauveria brongniartii strain JG-17 (1×10⁸ spores/mL), and the total protein content and the activities of the antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and the detoxification enzymes including carboxylesterase (CarE), glutathione S-transferase (GST) and acetylcholinesterase (AChE) in larvae of the three scarab species were determined at 1, 3, 5, 7, 9 and 11 d post infection (dpi). 【Results】 The SOD activities in larvae of the three scarab species infected by B. brongniartii strain JG-17 were activated at different dpi, with the SOD activity in H. oblita larvae responding faster than those in H. parallela and A. corpulenta larvae. The CAT activities in larvae of the three scarab species infected by B. brongniartii strain JG-17 showed a pattern of initial increase and subsequent decrease, with the CAT activity peaks in H. oblita, H. parallela and A. corpulenta larvae at 7, 7 and 9 dpi, respectively. These three infected scarab species displayed different change trends in POD activity. The POD activity in the infected H. parallela larvae by B. brongniartii strain JG-17 increased slowly from 1 to 7 dpi, and decreased significantly at 9 dpi, that in the infected H. oblita larvae showed an “M”-shaped change trend, and that in the infected A. corpulenta larvae increased significantly at 9 and 11 dpi. After infection by B. brongniartii strain JG-17, the GST activity showed a pattern of initial increase and subsequent decrease in the three infected scarab species. The GST activities in the infected H. oblita, H. parallela and A. corpulenta larvae increased significantly at 3, 5 and 7 dpi, respectively, while reached the peak at 5, 7 and 9 dpi, respectively, followed by decrease. After infection by B. brongniartii strain JG-17, the CarE activity decreased continuously in the infected H. parallela larvae throughout the experimental process, while displayed decrease following increase in H. oblita larvae. And the CarE activity in the infected A. corpulenta larvae increased continuously from 7 to 11 dpi. The AChE activity showed increase followed by decrease in larvae of the three scarab species infected by B. brongniartii strain JG-17, and the AChE activity and its change degree were higher in A. corpulenta larvae than in H. oblita and H. parallela larvae. 【Conclusion】Altogether, these results indicate the response mechanisms of enzymatic activities in these three scarab species against B. bassiana infection, providing valuable insights into insect immune responses and supporting the development of high-efficacy microbial insecticides.

Key words: Scarab beetles; Holotrichia oblita, H. parallela, Anomala corpulenta, Beauveria brongniartii; JG-17, antioxidant enzymes, detoxification enzymes