Butterflies released in Finland contained parasitic wasps – with more wasps inside

Introduction of Glanville fritillary leads to emergence of three new species on to Baltic Sea island

When caterpillars of a beautiful butterfly were introduced on to the tiny island of Sottunga in the Aland archipelago, scientists hoped to study how the emerging butterflies would disperse across the landscape.

But researchers did not realise that their introduction of the Glanville fritillary (Melitaea cinxia) led to the emergence of three other species on to the Baltic Sea island, which sprang out of the butterfly like Russian dolls.