Abstract <p>The rock grayling (<i>Hipparchia alcyone</i>) is one of the many butterfly species that has experienced a dramatic decline throughout Central Europe, but no empirical studies exist. This study provides information for conservation measures that protect the entire habitat of the open forests. We compared structures of currently with formerly colonised habitats. Therefore, we carried out vegetation assessments in the larval habitats in order to characterise these areas and derive changes in the habitat structures. The analyses revealed strong structural and qualitative differences between current and former habitats. Succession processes in the once highly unproductive habitats have led to far-reaching changes in environmental conditions. In particular, light supply and the abundance of the caterpillar food plant <i>Festuca ovina</i> are influenced by these changes. In this context, the encroachment of the neophytic <i>Prunus serotina</i> seems to be particularly problematic. In addition, a nectar source dependence on <i>Thymus serpyllum</i>, which is largely absent in the currently not colonised habitats, has to be assumed. The combination of these changes appears to have a negative impact on the butterfly’s populations.</p> Implications for insect conservation <p>To conserve <i>H. alcyone</i> in Central Europe, open forest structures must be preserved. Pine forests are no longer utilised continuously as in the past, which accelerates succession processes. In order to safeguard species in open forests, a balance must therefore be found between the endeavours of conventional forest conversion and the promotion of open forests. In addition, it is important to promote the supply of flowers, especially through the establishment of <i>T. serpyllum</i>. Overall, <i>H. alcyone</i> is assumed as an umbrella species for the habitat of open pine forests, and other species would also benefit from the mentioned measures.</p>