Post-diapause larval development

The Marsh Fritillary (Euphydryas aurinia) is a grassland butterfly protected throughout Europe (Habitats Directive, Annex II) and is widely regarded as a typical example of the decline of species-rich cultural landscapes. Most previous studies on this species have focused on adult butterflies, oviposition, or larval development during summer. In contrast, much less is known about the period after diapause in spring. A recent study published in the journal Insect Conservation and Diversity therefore investigated the phenology, developmental time, dispersal, and feeding behaviour of E. aurinia larvae after diapause in different grassland habitats. The study found that larvae show a high variability in developmental time after diapause and that dispersal and feeding behaviour differ markedly among the three larval instars examined. The time required for larvae to reach the 5th instar decreased with longer sunshine duration from January to March, higher litter cover, and a higher heat load index. While the very small 4th-instar larvae usually remained close to their hibernaculum and mainly fed on the leaves of Succisa pratensis, the larger 5th and 6th instar larvae increasingly dispersed and used a broader range of food resources, such as the flower buds of gentian species and Valeriana dioica. The use of a broad environmental gradient – and the associated extension of the developmental timing of different larval instars – may help E. aurinia cope with both the harsh climatic conditions in the study area and losses caused by specialized parasitoids such as braconid wasps. In the future, the landscape context should therefore be given greater consideration in conservation efforts for this species, and habitat heterogeneity should be promoted.

Scherer, G. & Fartmann, T. (2026): A protracted phenology: Post-diapause larval development of a threatened butterfly. Insect Conservation and Diversity 1–14. https://doi.org/10.1111/icad.70068