Scientific name: Satyrium w-album
A small butterfly which lives in the tops of elm trees throughout England and Wales, but is often overlooked.
Underwings brown with white W-shaped streak, an orange edge and small tails. Black Hairstreak is similar but has row of black spots on hindwing. The White-letter Hairstreak has the erratic, spiralling flight typical of Hairstreaks.
Difficult to spot as it flies around the tops of trees, particularly Elms. It occasionally comes down to ground level to nectar on flowers, especially privet and bramble.
The species declined in the 1970s when its foodplants were reduced by Dutch Elm disease, but it is recovering in a few areas.
Size and Family
- Family – Hairstreaks
- Small/Medium Sized
- Wing Span Range (male to female) - 36mm
- Listed as a Section 41 species of principal importance under the NERC Act in England
- Listed as a Section 41 species of principal importance under the NERC Act in Wales
- UK BAP status: Priority Species
- Butterfly Conservation priority: High
- European threat status: Not threatened
- Protected in Great Britain for sale only
The butterfly breeds on various elm species, including Wych Elm (Ulmus glabra), English Elm (U. procera), and Small-leaved Elm (U. minor). Research at one site has indicated a preference for (and a higher success rate on) Wych Elm. It breeds on mature trees or abundant sucker growth near dead trees. It has also been shown to survive on the Dutch Elm Disease-resistant variety of U. japonica, Sapporo Autumn Gold.
- Countries – England, and Wales
- Widespread in England and Wales, but rarer in the far west
- Distribution Trend Since 1970’s = Britain: -53%
The butterfly breeds where elms occur in sheltered hedgerows, mixed scrub and on the edges of woodland rides. The butterfly can also be found on large isolated elms.
- White-Letter Hairstreak Priority Species Factsheet
- Butterflies in towns and cities
- Woodlands for Butterflies and Moths