EN
Data on biology and ecology of the butterfly Oeneis jutta occurring within Poland territory are presented. Two confirmed sites of this species located in the Augustowska Primeval Forest, on a raised bog with pine tree stand and in a forest – peat bog complex are described. The only food plant for Oeneis jutta caterpillars is Eriophorum vaginatum. Adult butterflies fly c.a. six weeks, starting from the early days of May. Males appear 7-9 days before females. Peak appearance falls on the turn of May and June. In Poland the species has one-year life cycle, i.e. one generation per year and overwinters as larvae. The main predator is the dragonfly Orthetrum cancellatum.