| Family | Lycaenidae |
|---|---|
| Subfamily | Polyommatinae |
| Genus | Phengaris |
| Species | arion |
| Authority | (Linnaeus, 1758) |
| English Name | Large Blue |
| European Red List 2010 | Endangered (EN) |
|---|---|
| EU 27 Red List 2010 | Endangered (EN) |
| European Red List 2025 | Near Threatened (NT) |
| EU 27 Red List 2025 | Near Threatened (NT) |
| Habitats Directive | HD IV |
| Bern Convention | BC II |
| CITES |
The Large Blue occurs locally on dry, open grasslands on limestone. It is one of the larger, more conspicuous blues. The females lay their eggs on Marjoram (Origanum vulgare) and different species of thyme (Thymus spp.). The caterpillars feed on the buds and flowers of the foodplant until they reach the last larval instar. They then leave their foodplant, and allow themselves to be taken by workers of Myrmica sabuleti, and sometimes of M. scabrinodis, to the ants’ nest. The caterpillars feed on the ant grubs, hibernating and pupating in ants’ nests as well.
Albania / Andorra / Austria / Belarus / Belgium / Belgium: Wallonia / Bosnia and Herzegovina / Bulgaria / Croatia / Czechia / Denmark / Estonia / Finland / France / France: Mainland / Germany / Greece / Greece: Mainland / Hungary / Italy / Italy: Mainland / Latvia / Liechtenstein / Lithuania / Luxembourg / North Macedonia / Moldova / Montenegro / Netherlands (Regionally Extinct) / Poland / Romania / European Russia / Serbia / Serbia: Serbia / Serbia: Kosovo / Slovakia / Slovenia / Spain / Spain: Mainland / Sweden / Switzerland / European Türkiye / Ukraine / United Kingdom / United Kingdom: Great Britain /