Black Hairstreak (Satyrium pruni)
Species

Male. Taken at Whitecross Green Wood, Oxon., on June 6th 2018.
(1/640th sec at f11. Approx 3x lifesize. © David Hastings)

Female. Taken at Bernwood Forest, Bucks, on June 30th 2013.
(1/25th sec at f11. Approx 3x lifesize. © David Hastings)

Description

Wing span: 34 - 40 mm

The Black Hairstreak is one the rarest British butterflies and one of the most recently discovered, due to its similarity with the White-letter Hairstreak. The main distinguishing feature between the two species is that the Black Hairstreak has a row of distinctive black dots running along the inside of the orange band on the underside of the hindwing; these are absent in the White-letter Hairstreak. Males and females are similar, but the hindwing tails are longer in females.

This species has a very restricted distribution in England, which follows a line of clay soils between Peterborough and Oxford. It is widespread but patchily distributed in Europe.

Black Hairstreak colonies are typically located in small woods or nearby hedgerows, where stands of mature Blackthorn grow. Sites are located in sheltered but sunny positions and typically have a southerly aspect to them.

The flight period only lasts for 3 weeks, with the adults normally being seen in the second half of June and the first week of July. The ovum is the over-wintering stage, with the young caterpiller fully formed inside.

The primary larval foodplant is Blackthorn. Wild Plum is also used occasionally.

As well as aphid honeydew, adults will also take nectar from flowers such as Wild Privet, Dog Rose and Bramble.

Adults spend much of their time resting high up on Field Maple, Ash or Blackthorn, crawling over leaves and twigs in search of aphid honeydew. Males make short, looping flights in and out of the canopy; females are more sedentary.

This species has Endangered status on the UK list.

Sightings

18-Jun-2018 : Whitecross Green Wood, Oxon (8)
18-Jun-2018 : Otmoor, Oxon (5)
06-Jun-2018 : Otmoor, Oxon (8)
06-Jun-2018 : Whitecross Green Wood, Oxon (25+)

15-Jun-2017 : Whitecross Green Wood, Oxon (8)

26-Jun-2016 : Bernwood Forest, Bucks (1)
19-Jun-2016 : Whitecross Green Wood, Oxon (2m)

21-Jun-2015 : Otmoor, Oxon (4m,1f)
21-Jun-2015 : Whitecross Green Wood, Oxon (6m,1f)

15-Jun-2014 : Bernwood Forest, Bucks (6)
15-Jun-2014 : Whitecross Green Wood, Oxon (2)