| Family | Lycaenidae |
|---|---|
| Subfamily | Polyommatinae |
| Genus | Polyommatus |
| Species | eros |
| Authority | (Ochsenheimer, 1808) |
| English Name | Eros Blue |
| European Red List 2010 | Near Threatened (NT) |
|---|---|
| EU 27 Red List 2010 | Near Threatened (NT) |
| European Red List 2025 | Least Concern (LC) |
| EU 27 Red List 2025 | Least Concern (LC) |
| Habitats Directive | HD II IV ssp |
| Bern Convention | |
| CITES |
The Eros Blue is a mountain butterfly occurring on sub-alpine and alpine grasslands, on rocky places with flower-rich vegetation and on scree slopes. Purple Beaked Milk-vetch (Oxytropis halleri) and O. fetida are probably the major foodplants but other leguminous plants such as Astragalus sempervirens, A. leontinus, and Common Birdsfoot-trefoil (Lotus corniculatus) have also been named. The caterpillars feed on the leaves of the foodplant and hibernate on it. In spring, they grow further and when fully grown, pupate at the foot of the foodplants. They are attended by ants of the genera Myrmica, Formica and Camponotus. The Eros Blue has one generation a year.
Albania / Andorra / Austria / Belarus (Possibly Present) / Bosnia and Herzegovina / Bulgaria / Croatia / Czechia (Regionally Extinct) / France / France: Mainland / Germany / Greece / Greece: Mainland / Italy / Italy: Mainland / Liechtenstein / North Macedonia / Montenegro / Poland / European Russia / Serbia / Serbia: Serbia / Serbia: Kosovo / Slovakia (Regionally Extinct) / Spain / Spain: Mainland / Switzerland / Ukraine /