White-letter Hairstreak

Satyrium w-album

This record describes Satyrium w-album (species). Recorded family: Lycaenidae. Recorded order: Lepidoptera.

Identification and Appearance

White-letter Hairstreak - Satyrium w-album

This butterfly gets its name from the letter W that is formed from a series of white lines found on the underside of the hindwings. Elm is the sole foodplant especially Wych Elm. This species suffered as a result of Dutch Elm disease in the 1970s and early 1980s, especially in southern sites. It forms discrete colonies which are sometimes very small containing only a few dozen individuals. Colonies are typically focused on a small clump of trees or even an individual tree. These butterflies are not great wanderers and will reuse the same site year after year. Small colonies found throughout England, as far north as Lancashire and County Durham. It is found more locally in Wales. This species is not present in Scotland or Ireland.

Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Lycaenidae
Genus: Satyrium

Imported taxonomy record. Source availability varies; see the source references and editorial policy below.

Habitat and Range

Habitat

Around the tops of Elm trees.

Seasonal Activity

Late June to mid August.

Diet and Behavior

Life History

Elm is the sole foodplant especially Wych Elm. This species suffered as a result of Dutch Elm disease in the 1970s and early 1980s, especially in southern sites. It forms discrete colonies which are sometimes very small containing only a few dozen individuals. Colonies are typically focused on a small clump of trees or even an individual tree. These butterflies are not great wanderers and will reuse the same site year after year.

Additional species information

Recorded status

Small colonies found throughout England, as far north as Lancashire and County Durham. It is found more locally in Wales. This species is not present in Scotland or Ireland.

About Butterflies and Moths: the wider group

Order-level background for Lepidoptera, the group containing Satyrium w-album. Species-specific details appear above.

Group overview

Lepidoptera includes approximately 180,000 described species of butterflies and moths. Moths outnumber butterflies roughly 10:1. The monarch butterfly's eastern population has declined by more than 80% since the mid-1990s, and the western population by over 95% since the 1980s. The IUCN lists the migratory monarch as Vulnerable.

Ecological role of the group

Butterflies and moths are essential indicators of ecosystem health. As caterpillars, they are a primary food source for birds - a single nest of blue tit chicks requires ~10,000 caterpillars. Adult moths pollinate many night-blooming plants.

Economic and practical significance of the group

Lepidoptera are critical pollinators. In Europe, grassland butterfly species have declined by almost 50% since the early 1990s. In the UK, three-quarters of butterflies are in decline. In the U.S., five butterfly species have gone extinct since 1950, with 29 listed as endangered.

Recorded sources for this group: IUCN Red List, Xerces Society, USFWS, PNAS, WWF. Imported estimates may describe particular regions or reporting periods.

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