Butterfly-ant relationships : host ant specificity of Phengaris 'rebeli' Hirschke (Lepidoptera: Lycaenidae) in Pieniny Mts. (Southern Poland)

Phengaris 'rebeli' Hirschke is a globally threatened obligatorily myrmecophilous and xerothermophilous butterfly. Caterpillars are initially endophytic and feed in flowerheads of Gentiana cruciata L. but they complete their development as social parasites of Myrmica Latr. ants. Relationships with hosts are specific and show geographical variation in Europe. Knowledge on them is vital for effective conservation. In Poland 'P. rebeli' was recorded from a dozen or so sites in the SE part of the country and from one locality in the Pieniny Mts. - a low calcareous mountain range on the Polish-Slovak border that constitutes a distinct geobotanical unit with specific climate and diversity of habitats. Present studies aimed to identify hostants of the butterfly in the Pieniny Mts. A total number of 30 Myrmica colonies were searched in 2008 near larval food plants bearing eggs of 'P. rebeli' in the previous season. We observed caterpillars and pupae of the butterfly exclusively in nests of M. schencki Em., i.e. 4 of 4 of them were infested. However, we did not find prematures of P. 'rebeli' with M. sabuleti Mein., M. rugulosa (Nyl.) and M. rubra (L.) which were also present in the turf. This makes the Pieniny population completely distinct from previously studied populations in SE Poland and similar to those known from Lithuania, France and Spain. It is probably related to the variation in chemical mimicry of P. 'rebeli' caterpillars. Our finding contributes to knowledge on the pattern of host-ant use of the butterfly in Europe and is also important for conservation on a local scale.