Does climate change affect overwintering forest invaders? Physiological responses of the emerald ash borer (Coleoptera: Buprestidae) to mid-winter warm spells

North American winters are subject to climate change effects such as sudden warm spells in mid-winter, where temperatures can rise well above 0°C for an extended period of time. If physiological responses in overwintering insects do not allow for coping with these fluctuating temperatures, mortality might increase and possibly halt invasions by limiting a species’ range. We exposed overwintering prepupae of the invasive wood-boring beetle Agrilus planipennis to different winter temperature regimes and investigated plasticity in cold hardiness and the related mechanisms. Mid-winter warm spells at or above 10 °C resulted in deacclimation with significantly increased supercooling points after several days. Transfer to -10 °C after warm exposure showed some reacclimation, but the prepupae did not freeze at the low temperatures observed prior to the experiments. Hemolymph samples will be analyzed to investigate if carbohydrates and antifreeze proteins play a role in the observed patterns.