In summer 1992 a butterfly inventarory was made in the ‘Woldlakebos’. This nature reserve consists of woods in a drained marshland area with water-filled ditches and a wide variety of vegetation. Results of the survey are given together with a detailed description of the biotops. A comparison was made with the observed species as mentioned in the Atlas of Dutch Butterflies. Special attention is given to the species Clossiana selene, its biotop, its flight behaviour, and management measures to preserve the species.