Effects of soil humidity on respiration and frost resistance during winter diapause in the pine beauty moth, Panolis flammea

Abstract

Abstract Panolis flammea is an important pest whose populations intermittently outbreak in Europe. The species overwinters as pharate moths in the pupal stage in soil. Details on the metabolic activity and cold hardiness of P. flammea during the overwintering period have not been published. Therefore, we assessed O2 consumption and the supercooling point (SCP) of P. flammea in late November, mid‐February, and mid‐March and the influence of soil humidity under fluctuating temperatures and with brief exposures to two increased temperature regimes (10 and 20°C). The respiration pattern indicated diapause termination in mid‐February. A threshold of 0.169 μl O2 h−1 mg−1 fresh weight indicated potentially activated pre‐emerging moths. Drought increased respiration rates. The SCP was lowest in mid‐February (−22.2°C) and was negatively correlated with pupal mass. The frost tolerance tended to increase with low substrate humidity, especially at the end of the overwintering period. Our results indicate that P. flammea requires more energy during dry and mild winters than in wet and cold winters. Winter diapause termination and post‐diapause development may therefore be accelerated as environmental warming and drought increase.