Scientific name: Satyrium pruni
The Black Hairstreak is one of our rarest and most elusive butterflies, staying in the tree canopy feeding on aphids and spending little time in flight.
It is found only in thickets of Blackthorn in woodlands on heavy clay soils, between Oxford and Peterborough in the East Midlands of England. It lives within a very small range and has declined due to changes in woodland management.
The underwings are brown with a tinge of gold and the borders are orange, with a row of black spots, a white streak down each wing and small tails. The upperwings are only ever visible in flight (the butterfly always settles with its wings closed) and are brown with an orange patch on each forewing and orange tails on the lower wings.
When in flight, the adults can easily be confused with White-letter Hairstreaks, which fly in the same habitat and at the same time of year, although the White-letter lacks the row of black spots and has a more obvious W-shaped streak on the underside.
The adults spend nearly all their time in the canopies of trees of dense scrub, where they feed on honeydew secreted by aphids. At certain times they make short looping flights in and out of the tree tops, with a peak of activity around midday.
The textured disc-shaped eggs change colour as they age, from a blue-green on being laid, to dark brown and eventually faiding to a pale grey-brown, although algae can affect the colour. The eggs are laid singly in the base of Blackthorn twigs, where their camouflage helps them look like buds. Most of the life of this butterfly is spent as an egg.
The caterpillar also changes colour as it grows, starting off plain brown, then brown with a white saddle, then a solid green until its final stage when it becomes a pale transluscent striped green, with pink tipped ridges along its back. It is camouflaged to resemble the blackthorn leaves on which it mostly feeds, until it pupates in spring.
The chysalis is camouflaged black and white to mimic a bird dropping and is usually found on a Blackthorn leaf or twig.
The Black Hairstreak declined steadily during the twentieth century and is now reduced to around 50 sites.
Size and Family
- Family: Hairstreaks
- Size: Small/Medium
- Wing Span Range (male to female): 37mm
- Butterfly Conservation priority: High
- Protected under Schedule 5 of the Wildlife and Countryside Act (for sale only)
- A regional priority in East Midlands, East of England and South East England.
Blackthorn (Prunus spinosa) is almost exclusively used, but occasionally Wild Plum (P. domestica) and other Prunus species are used.
Most colonies breed in dense mature stands of Blackthorn growing in sunny, sheltered areas - usually along wood edges, edges of rides and glades or hedgerow thickets. Some smaller colonies occur in shady situations such as canopy gaps in mature woodland, small scrub patches or sheltered hedgerows.
- Countries: England
- Restricted to a small belt of central England running approximately from Oxford to Peterborough
- Distribution Trend Since 1970’s = - 43%