Winter dormancy in the spongy moth parasitoid Glyptapanteles liparidis and its potential overwintering host Lasiocampa quercus

Winter dormancy is a recurring period of suspended development and reproduction, allowing insects to survive harsh conditions. It may occur as an immediate response to adverse conditions (quiescence), or as diapause, a more complex and dynamic process. Facultative diapause is triggered by specific environmental cues that precede unfavourable conditions, typically by decreasing photoperiod. Obligate diapause is genetically fixed, independent of environmental conditions. Winter dormancy is associated with reduced activities and metabolic adjustments. The oligophagous, koinobiont endoparasitic wasp Glyptapanteles liparidis is a key natural enemy of the spongy moth, Lymantria dispar, a major defoliating pest in oak forests. Despite of a long history of research in this parasitoid-host-system, the overwintering biology of G. liparidis is still poorly understood. Eggs or first instar wasp larvae overwinter inside a caterpillar host. Since the univoltine spongy moth passes the winter months inside the egg, the multivoltine G. liparidis is dependent on alternative lepidopteran hosts that overwinter as larvae. A possible overwintering host is Lasiocampa quercus, a common species in oak forests with a wide ecological amplitude. The moth passes the winter months as early or intermediate instar larva; however, their overwintering biology has not been studied sufficiently. Our goal is to investigate the overwintering strategy of the parasitic wasp and its potential overwintering host, and whether the system might also be susceptible to asynchronicity due to changing environmental conditions. We will characterize and compare the induction, duration, and depth of winter dormancy in G. liparidis and L. quercus in laboratory and semi-field trails. Specifically, various day lengths and temperature combinations will be used in different phases of the life cycle of host and parasitic wasp. Parasitized hosts will be dissected at specific intervals to determine the developmental progress of the wasp larvae inside the host. Metabolic changes such as food consumption and feces production, oxygen consumption, the ability to supercool, and specific metabolites such as glycogen, trehalose, polyols, amino acids, and proteins will be assessed.