Boloria euphrosyne (Linnaeus, 1758)

Host plants:
The larva develops on Viola species such as Viola hirta and Viola reichenbachiana.

Habitat:
Boloria euphrosyne inhabits nutrient-poor, bushy grasslands often near the woods, fringes and clearcuts in the forest and forest gap systems in the Alps. In the south it also occurs in the Maquis and Garigue and in clear oak woods. Boloria euphrosyne belongs to the first species in clearcuts, as the larva needs only partially overgrown ground. There it basks on moss, pieces of bark in the early spring, as own observations show. If the vegetation becomes too dense, Boloria euphrosyne disappears soonly while Boloria selene lasts longer or reaches its optimum not until higher and denser growth on the clearing.

Life cycle:
The caterpillar overwinters as L4 and is mature in April/early May or in higher elevations until June. I found the caterpillar several times in the Allgäu Alps in Germany (in May) and the Valais (May and June) at the edges of woods and slopes in the forest. During the daytime, the caterpillars often rest between short periods of feeding and basking well concealed in the litter for longer time.

The adults fly between late April and early July. Despite the in comparison to Boloria selene earlier appearance no second generation is created. The caterpillars do not need any frost during diapause, so that two or three months refrigerator at 5 degrees Celsius suffice. This allows Boloria euphrosyne the colonization of the Mediterranean region.

Endangerment: endangered

Endangerment factors:
Boloria euphrosyne is much more threatened than Boloria selene north of the Alps because the butterfly is affected by darkening processes in forests and rapid overgrowth of clearcuts very quickly. Near Memmingen (Germany) in the 80s yet very individual-rich populations are largely collapsed in recent years. Boloria euphrosyne is still more common only in the Alps and in regions that are rich in bushy grasslands near woods and clearcuts as the Swabian Alb.
In the south (e.g. Provence) the threat is much lower.

Remarks:
The total distribution ranges from Northern Spain across much of Europe and temperate Asia to Kazakhstan. Boloria euphrosyne is quite common in the Alpine region (up to about 2000m in the Valais) and the northern Mediterranean (e.g. Provence).