Widespread but local in the mountains at moderate altitudes where it's foodplant, the blue-flowered Cross (or Star) Gentian (Gentiana cruciata) grows.
Like the large Blue (Phengaris arion), larval development begins on the hostplant but is completed within the nest of red ants (one of three species: Myrmica ruginodis, M. rubra or M scabrinodis). Unlike the Large Blue, several larvae may develop in a single ants nest (up to 20, Thomas & Elmes 1998), and occasionally one may come across several newly emerged adults in one place.
In Bulgaria adults are on the wing from late June and through July. Often the presence of the butterfly can most easily be detected by looking for the eggs towards the base of the upper leaves of the hostplant (see photo).
Athought the butterfly is quite still widespread in Bulgaria, it has probably declined appreciably in recent decades due to the abandonment of traditional farming practices, and this decline is likely to continue.
Herb-rich grassland where the hostplant grows.
Recorded in 7 (0.4%) of the 1900 10km squares of Bulgaria.
Last recorded in July 2017
Recorded date range (Adult): 30 June to 22 July