Metabolic and survival responses to high temperature stress in the red-haired pine bark beetle Hylurgusligniperda

Hylurgus ligniperda, a pine-infesting bark beetle, has successfully invaded Shandong, China, through imported forest timber, posing a significant threat to the country's forestry security. Heat tolerance is a critical survival strategy for insects to endure high summer temperatures, and understanding its mechanisms in H. ligniperda could improve pest forecasting and habitat suitability predictions. In this study, we investigated heat-induced mortality and physiological responses of H. ligniperda under various high-temperature conditions. Our findings revealed that elevated temperatures significantly reduced survival rates of both adults and larvae, with Lt₅₀ (time to 50 % mortality) declining as exposure temperature increased. Notably, H. ligniperda adults exhibited higher heat tolerance than larvae. At 30 °C or 35 °C, water and trehalose content in adults progressively decreased with prolonged exposure (4-12 h). Conversely, lipid, protein, and glycerol levels declined as temperature increased at fixed exposure durations (4, 8, or 12 h). We concluded that short-term extreme heat directly reduced adult survival rates and was associated with depletion of energy reserves (lipid, glycogen, and protein) and dynamic changes in protective molecules (trehalose, sorbitol, and glycerol). This correlation suggests a protective mechanism that mitigates heat damage in H. ligniperda. This study provides foundationalinsights into the heat tolerance strategies and metabolic adaptations of H. ligniperda adults, offering critical data for predicting its spread under climate change scenarios.