The first observation of Euphydryas aurinia (Lepidoptera, Nymphalidae) developing on Gentiana cruciata in Lithuania

A population of the endangered butterfly Marsh Fritillary Euphydryas aurinia, using exclusively Gentiana cruciataas a larval food plant, was recorded for the first time in the valley of the Dksta river (Vilnius administrative district) in Lithuania . Caterpillarswere observed both in summer when they lived gregariously in numerous webs spun on gentians, and in spring when they were feeding on new shoots or basking in the sun. The butterfly is considered as dependent on Suc- cissa pratensis in Central and Northern Europe, therefore our finding is unexpected. Other plants including other Gentianaspecies are reported as locally used only in Southern Germany, Switzer- land and Spain. Phengaris'rebeli ' a well known butterfly related to G. cruciataoccured sympatri- cally with E. auriniaat the Lithuaniansite.