White-letter Hairstreak - Appearance, Behaviour and Distribution

Appearance, Behaviour and Distribution

A dark little butterfly that spends the majority of its life in the tree tops, feeding on honeydew, making it best observed through binoculars. The uppersides are a dark brown with a small orange spot in the bottom corner of the hindwing. The male has a small pale spot on the forewings made up of scent scales. The undersides are a lighter brown with a thin white line, the 'hairstreak' which gives this group of butterflies their name. On the hindwing this streak zigzags to form a letter 'W' (or 'M') from which this species gets its name. The outer edge of the hindwing has an orange border, but there is no orange on the forewings like the similar Black Hairstreak and there are two short tails on the hindwings.

Part of a group known as "lateral baskers", they always rest with their wings closed. Widely but patchily distributed across most of England it is absent from Scotland, Ireland, western Wales and most of Cornwall. The spread of Dutch Elm Disease in the 1970s inevitably had a major impact on the British population but it has since recovered well in places and is still increasing its range. The insect has a widely disjunct distribution across the northern hemisphere. It is found throughout much of Europe, including Scandinavia, as far as the Urals, and occurs again in the Far East, including Japan. It is absent from North America.

In order to safeguard the future of this butterfly, some conservation organisations within the UK, such as the Hampshire and Isle of Wight branch of Butterfly Conservation and the Forestry Commission, have planted disease-resistant cultivars, notably 'Morfeo'. The beetle-resistant European White Elm Ulmus laevis has also been planted, notably by the Cheshire Wildlife Trust. More details about these projects can be found in the References section of this article.