Thermal tolerance responses of the two-spotted stink bug, Bathycoelia distincta (Hemiptera: Pentatomidae), vary with life stage and the sex of adults

Temperature tolerance is an essential component of insect fitness, and its understanding can provide a predictive framework for their distribution and abundance. The two-spotted stink bug, Bathycoelia distincta Distant, is a significant pest of macadamia. The main goal of this study was to investigate the thermal tolerance of B. distincta across different life stages. Thermal tolerance indices investigated included critical thermal maximum (CTmax), critical thermal minimum (CTmin), effects of acclimation on CTmax and CTmin at 20, 25, and 30 ◦C, and rapid heat hardening (RHH), and rapid cold hardening (RCH). The Kruskal-Wallis test was used to explore the effects of life stage and acclimation on CTmax and CTmin and Generalized Linear Models (GLM) for the probability of survival after pre-exposure to RHH at 41 ◦C for 2 h and RCH at 8 ◦C for 2 h. CTmax and CTmin varied significantly between life stages at all acclimation temperatures, but CTmin (3.5 ◦C) varied more than CTmax (2.1 ◦C). Higher acclimation temperatures resulted in larger variations between life stages for both CTmax and CTmin. A significant acclimation response was observed for the CTmax of instar 2 (1.7 ◦C) and CTmin of females (2.7 ◦C) across acclimation temperatures (20–30 ◦C). Pre-exposure significantly improved the heat and cold survival probability of instar 2 and the cold survival probability of instar 3 and males. The response between life stages was more variable in RCH than in RHH. Instar 2 appeared to be the most thermally plastic life stage of B. distincta. These results suggest that the thermal plastic traits of B. distincta life stages may enable this pest to survive in temperature regimes under the ongoing climate change, with early life stages (except for instar 2) more temperature sensitive than later life stages. Keywords: CTmax, CTmin, Acclimation, RHH, RC