| Family | Lycaenidae |
|---|---|
| Subfamily | Polyommatinae |
| Genus | Iolana |
| Species | iolas |
| Authority | (Ochsenheimer, 1816) |
| English Name | Iolas Blue |
| European Red List 2010 | Near Threatened (NT) |
|---|---|
| EU 27 Red List 2010 | Near Threatened (NT) |
| European Red List 2025 | Near Threatened (NT) |
| EU 27 Red List 2025 | Near Threatened (NT) |
| Habitats Directive | |
| Bern Convention | |
| CITES |
The Iolas Blue is Europe’s largest blue. It occurs locally on calcareous soil, where shrubs of its foodplant Bladder Senna (Colutea arborescens) are growing. In Greece, C. cilicica is also used. This plant is practically the most important source of nectar for the butterflies. At times, the males can be seen some distance away from their habitat, but the females stay near the foodplants. They lay their eggs, usually several at a time, on the inside of the calyx and inside the bladder-like fruits. The caterpillars feed on the seeds and are visited frequently by ants (e.g. Tapinoma erraticum and Camponotus cruentatus). Usually, they can easily be seen by holding a pod up to the light. When fully-grown, the caterpillars pupate at the foot of the foodplant, passing the winter as a pupa. The Iolas Blue mostly has only one generation a year.
Albania / Austria (Irregular Vagrant) / Bosnia and Herzegovina / Bulgaria / Croatia / France / France: Mainland / Greece / Greece: Mainland / Greece: East Aegean Islands / Hungary / Italy / Italy: Mainland / North Macedonia / Montenegro / Romania / Serbia / Serbia: Serbia / Serbia: Kosovo / Slovakia (Regionally Extinct) / Slovenia / Switzerland /