| Family | Lycaenidae |
|---|---|
| Subfamily | Theclinae |
| Genus | Satyrium |
| Species | w-album |
| Authority | (Knoch, 1782) |
| English Name | White-letter Hairstreak |
| European Red List 2010 | Least Concern (LC) |
|---|---|
| EU 27 Red List 2010 | Least Concern (LC) |
| European Red List 2025 | Least Concern (LC) |
| EU 27 Red List 2025 | Least Concern (LC) |
| Habitats Directive | |
| Bern Convention | |
| CITES |
The White-letter Hairstreak usually occurs where there is a group of elm (Ulmus spp.) trees, either growing in a wood, or apart, sometimes even in the centre of a large town. However, there are populations known that occupy a solitary tree. The eggs are laid on the wood at the base of the flower buds, the female favouring terminal buds situated at the top of the tree. The small caterpillar stays inside the egg during the winter months, emerging in the spring, boring its way into a flowerbud. It feeds on flowerbuds and flowers, but not on leaves. A non-flowering tree is therefore not a suitable foodplant. The caterpillars are sometimes visited by ants of the genus Lasius and Formica and pupate in the litter layer under the tree. The White-Letter Hairstreak has one generation a year.
Albania / Andorra / Austria / Belarus / Belgium / Belgium: Flanders / Belgium: Wallonia / Bosnia and Herzegovina / Bulgaria / Croatia / Czechia / Denmark / Estonia / Finland / France / France: Mainland / France: Corsica / Germany / Greece / Greece: Mainland / Hungary / Italy / Italy: Mainland / Italy: Sicily / Latvia / Liechtenstein / Lithuania / Luxembourg / North Macedonia / Moldova / Montenegro / Netherlands / Norway / Poland / Romania / European Russia / San Marino / Serbia / Serbia: Serbia / Serbia: Kosovo / Slovakia / Slovenia / Spain / Spain: Mainland / Sweden / Switzerland / European Türkiye / Ukraine / United Kingdom / United Kingdom: Great Britain / United Kingdom: Guernsey (Possibly Present) / United Kingdom: Jersey /