Effects of High Temperature on Development, Survival, and Antioxidant Responses of Immature Monolepta hieroglyphica

Monolepta hieroglyphica Motschulsky (Coleoptera: Chrysomelidae) (M. hieroglyphica) is widely distributed in China. Its larvae are soil pests that cause severe damage to the seeds and roots of economically important crops such as corn, cotton, and millet. This study investigated the effects of four temperatures (25, 28, 31, and 34 °C) on the survival rate, food consumption (3rd instar), pupation rate, emergence rate, biometric indices (weight and length), and antioxidant enzyme activity of immature M. hieroglyphica. High temperatures (31 °C and 34 °C) adversely affected developmental duration, survival rates, and feeding efficiency. The highest pupation rate, emergence rate, and biometric indices were observed at 28 °C, after which these metrics steadily declined as the temperature increased. Notably, emergence was completely inhibited at 34 °C, resulting in the absence of biometric data. These changes correspond with the temperature-dependent regulation of antioxidant enzyme activities (SOD, CAT, GST, and POD). This study identified the optimal temperature range and critical high-temperature threshold for immature M. hieroglyphica, providing key biological parameters for predicting population dynamics and outbreak risks under climate warming, and offering a scientific basis for precise monitoring and temperature-based integrated pest management strategies.