Abstract The Marsh Fritillary ( Euphydryas aurinia , Rottemburg, 1758) is a grassland butterfly that has experienced severe population declines across Europe during the last century. Most studies on this species have focused on adults, oviposition or pre‐diapause larvae. By contrast, knowledge on the time after diapause in spring is scarce. Here, we studied phenology, developmental time, dispersal and feeding behaviour of post‐diapause larvae of E. aurinia in montane grasslands in the Bavarian Alps (Central Europe). Our study revealed that after diapause, larvae exhibited a strong variability in developmental time as well as pronounced differences in the dispersal and feeding behaviour between the three instars. Developmental time of post‐diapause larvae to reach the 5th instar decreased with longer sunshine duration during January to March, higher litter cover and higher heat load index. In dry meadows, larvae reached the 5th instar in about 2 weeks after finishing diapause—nearly 2 weeks earlier than in wet grasslands in some cases. In contrast to the tiny 4th instar larvae, which stayed close to their hibernaculum web and primarily fed on Succisa pratensis leaves, larger 5th and 6th instar larvae increasingly dispersed and diversified their feeding behaviour. We hypothesize that occupying a large environmental gradient, resulting in a protracted phenology of the different instars, helps E. aurinia to cope with the harsh climatic conditions in the study area and losses by specialized parasitoids like braconid wasps.
Scherer et al. (Thu,) studied this question.