Scientific name: Thecla betulae
The largest hairstreak in the UK is an elusive butterfly that spends most of its time either high in the canopy of trees, or hiding in hedgerows.
It is worth looking up at prominent Ash trees along wood edges to see if small clusters of adults may be flitting around. They congregate to mate and feed on aphid honeydew. Adults also sometimes feed lower down, on flowers such as Hemp-agrimony, Common Fleabane and Bramble. The females are most frequently seen, as they disperse widely along hedgerows where they lay conspicuous white eggs on young Blackthorn shoots.
The butterfly usually rests with its wings closed. The underwings feature two wavy white streaks with small tails on the hindwings. The colour of the male's underwings are a lighter orange that those of the female and the female has longer tails than the male. Both have brown uppersides; the male's with a smallish yellow mark and the female's with a large, orange mark.
The tiny, white and pin-head sized eggs are laid singly and can easily be found during the winter in the forks or notches of young Blackthorn twigs.
The caterpillar is a well-camouflaged pale green with faint yellow stripes, triangular-shaped and rather slug-like. It can be found underneath Blackthorn leaves in June.
The chysalis is much harder to find, being a purplish-brown and fairly featureless and lying on the ground in leaf litter for around a month.
The Brown Hairstreak is locally distributed in southern Britain and mid-west Ireland. It has undergone a substantial decline due to hedgerow removal and annual flailing, which removes eggs.
Size and Family
- Family: Hairstreaks
- Size: Small/Medium
- Wing Span Range (male to female): 38-40mm
- Section 41 species of principal importance under the NERC Act in England
- Section 42 species of principal importance under the NERC Act in Wales
- UK BAP status: Priority Species
- Butterfly Conservation priority: High
- European Status: Not threatened
- Protected under Schedule 5 of the 1981 Wildlife and Countryside Act (for sale only)
The butterfly breeds on the young growth of Blackthorn (Prunus spinosa) and occasionally other Prunus species such as Bullace (P. domestica).
As the primary larval plant is Blackthorn, the Brown Hairstreak can be found wherever this shrub is established and not flailed annually, such as hedges, scrub and woodland.
- Countries: England, Wales, and Ireland
- Restricted in the UK to three main centres: south-west Wales, Devon/Somerset and Surrey/Sussex. Other smaller populations occur around Oxford and on Salisbury Plain.
- Distribution Trend Since 1970’s = -43%.
- Butterflies and farmland
- Hedgerows for Hairstreaks
- Woodlands for Butterflies and Moths
- Brown Hairstreak in Blackdown Hills Leaflet
- Y Brithribin Brown_bh_Cym
- Brown Hairstreak in Wales v2009