Overview of Implemented Measures

For the captive breeding and reintroduction of the marsh fritillary (Euphydryas aurinia), caterpillars were collected from suitable sites with stable populations (including the Westerwald, Eifel, and Rhön regions). The goal is to establish a stable population in the project area in the coming years using the bred individuals. The breeding program is carried out in cooperation with the LIFE project “helle Eifeltäler,” which also focuses on the reintroduction of this species. We greatly value the mutual support and professional exchange.

First attempt (September 2022)

In September 2022, following prior mapping of caterpillars in the Westerwald district, several larval nests of the marsh fritillary were collected from the Fuchskaute Nature Reserve. The caterpillars were used for captive breeding by butterfly breeder Wolfgang Losert. Unfortunately, this attempt was unsuccessful, as all caterpillars died. The exact cause is unknown, but unfavorable weather conditions likely played a role. Spring 2023 was exceptionally wet and cold at times, which likely affected butterfly development. These climatic effects were also reflected in butterfly monitoring results.

Second attempt (September 2023)

In September 2023, after population declines were observed in Rhineland-Palatinate and the species was no longer detectable at the Breitbach reservoir, another collection of caterpillars was carried out together with the partner project “LIFE helle Eifeltäler”. This was done in close coordination with the SGD Nord and the site manager of the Fuchskaute Nature Reserve.

The caterpillars were transferred in their larval webs along with their food plant, devil’s-bit scabious (Succisa pratensis), and surrounding soil to avoid damaging the webs. A total of four larval webs were collected, two of which were managed in the Eifel and two by our project team.

In spring 2024, the caterpillars developed normally and began to pupate. A total of 10 butterflies emerged. However, no mating or egg-laying occurred. Additionally, each larval web contained only between 30 and 70 caterpillars.

Third attempt (June 2024)

In June 2024, six egg batches were collected from the Rhön (nature reserve) in cooperation with the project “LIFE Rhöhner Bergwiesen” . In September, three additional larval webs were received from the partner project “LIFE helle Eifeltäler”.

In spring 2025, more than 1,000 caterpillars emerged from hibernation and fed on young devil’s-bit scabious plants. Over the course of spring, they pupated and developed into butterflies.

In June 2025, a total of 88 egg batches were recorded in the aerarium. The prospects for a second release in spring 2026 are very promising.

A new aerarium for breeding (May 2025)

As the caterpillars grew, the original aerarium became too small. The animals developed rapidly and required increasing amounts of food plants. Therefore, a new, larger, and more stable aerarium was constructed, providing significantly more space for both caterpillars and emerging butterflies. It allows safe handling without disturbing the sensitive breeding process.

The food plants and additional flowering plants were carefully relocated and rearranged, ensuring a diverse and natural food supply for both caterpillars and adult butterflies.

Our breeding experience so far shows that weather conditions play a crucial role in success. The first two attempts in spring 2023 and 2024 were unsuccessful, both characterized by cold and wet conditions. Butterfly monitoring in the project area also recorded only few observations during these years.

In contrast, spring 2025 was warm and dry. Under these favorable conditions, breeding was successful, and monitoring recorded a significantly higher number of butterflies.

First Release (May 2025)

After months of care in our protected aeraria, marsh fritillary caterpillars were reintroduced to the FFH site "Buchheller-Quellgebiet" for the first time. This rare butterfly had last been observed in the area eleven years ago, and now we hope that the 160 released caterpillars will lay the foundation for a new population.

The caterpillars were transported in small jars with devil’s-bit scabious leaves. On-site, they were placed on devil’s-bit scabious plants within a rotational fallow. By the next day, they were already actively feeding. At this point, the caterpillars had reached their final larval stage and pupated in the following days.

About three weeks later, the first butterflies were observed.