Field Guide
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Black Hairstreak
Strymonidia pruni
Not yet photographed by the community
Very restricted range; blackthorn woodland specialist.
Species Profile
UK Amber List; listed as a Nationally Scarce species (Na) due to habitat loss and its highly localised distribution.
- Lifespan
- Approximately 2–3 weeks as an adult butterfly in the wild
- Size & Weight
- Wingspan 27–32 mm
- Habitat
- Woodland edges, scrubland, and sheltered areas where blackthorn (Prunus spinosa) is abundant, typically in warm, sheltered locations.
- UK Distribution
- Resident and localised to southern England, primarily in the Midlands and south-central regions; a scarce and declining butterfly with a fragmented range.
- Diet
- Adults feed on honeydew from aphids and small quantities of nectar; caterpillars are monophagous, feeding exclusively on blackthorn leaves.
- Predators
- Spiders, robber flies, and insectivorous birds such as redstarts and warblers.
- Mating Season
- July to August
- Breeding
- Females lay eggs singly on blackthorn twigs in late summer; eggs overwinter and hatch in spring; single brood per year.
- Behaviour
- Males are notably pugnacious and territorial, perching on low vegetation to intercept females and rival males; they have a characteristic rapid, jerky flight. Adults spend much time resting on blackthorn stems with wings closed.
- •The Black Hairstreak is one of the UK's rarest and most localised hairstreak butterflies, with populations restricted to just a handful of sites.
- •Its caterpillars feed exclusively on blackthorn, making the butterfly entirely dependent on this native shrub for reproduction.
- •Males have distinctive black upperside colouring with orange spots on the hindwings, while females are slightly larger and duller.
- •The species has declined significantly due to loss and fragmentation of blackthorn scrubland and inappropriate woodland management.
- •Adults have a very short flight period of only 3–4 weeks in mid-to-late summer, making sightings rare and sought-after by butterfly enthusiasts.
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