The underwings are brown, with a white W-shaped streak, an orange edge and small tails. The Black Hairstreak is similar, but has a row of black spots on the hindwing. The White-letter Hairstreak has the erratic, spiralling flight typical of Hairstreaks.
It is 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
- Size: Small/Medium
- Wing Span Range (male to female): 36mm
- Butterfly Conservation priority: High
- Section 41 species of principal importance under the 2006 NERC Act in England
- Section 41 species of principal importance under the 2006 NERC Act in Wales
- UK BAP status: Priority Species
- Protected under Schedule 5 of the 1981 Wildlife and Countryside Act (for sale only)
- European threat status: Not threatened
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.
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.
Distribution and Abundance
- Countries: England and Wales
- Widespread in England and Wales, but rarer in the far west.
- Distribution Trend Since 1970’s = -45%
- Population Trend Since 1970's = -93%
White-Letter Hairstreak Priority Species Factsheet
pdf 201.99 KB