White-letter hairstreaks are small butterflies that breed on elm trees. These small butterflies prefer the tops of the trees so are hard to spot and easily missed.
How to identify
Key identification features of this small brown butterfly are the small hairs located at the base of the wings and the white W-shaped line on the underside of the wing, from which it gains its name.
Where to find it
Mostly in England and Wales, with a few isolated records in Scotland.
When to find it
How can people help
White-letter hairstreaks are estimated to have suffered a 99% population decline over the last 25 years in the UK. The eggs of white-letter hairstreaks are laid on elm trees, which the caterpillars feed on in spring and the decline may in part be due to the loss of their larval food plant due to Dutch elm disease. If you have hedges with elm trees where white-letter hairstreaks may be present, encourage the presence of food plants such as bramble or hogweed. This species may also be under-recorded so please report any sightings to your county Wildlife Trust or biological record centre.