Thymelicus acteon is a former resident; it has been extinct since 1981. At the beginning of the 20th century, it was common in the southern part of the province of Limburg, but gradually declined, becoming very rare in the 1960s. It occurred in the rougher parts of limestone grassland, where the caterpillar was mainly found in large tussocks of Brachy-podium pinnatum, its larval foodplant. The species flew in one generation from mid-July until mid-August, and hibernated as a young caterpillar. Its disappearance was probably largely due to habitat loss: many limestone grasslands had been taken into cultivation or managed inappropriately, for example, by burning or abandonment. However, if the calcareous grassland reserves where it formerly occurred are managed appropriately, butterflies from neighbouring Belgian populations may recolonise them.
Wynhoff, I., Swaay, C. van, Groenendijk, D., Bosveld, M., Bos, F.
- Bos, F., M. Bosveld, D. Groenendijk, C. van Swaay & I. Wynhoff 2006. De dagvlinders van Nederland, verspreiding en bescherming. Nederlandse Fauna 7. De Vlinderstichting, Wageningen en Nationaal Natuurhistorisch Museum Naturalis, European Invertebrate Survey, Nederland.