The Black Hairstreak is one of our rarest butterflies and one of the most recently discovered, due to the similarity with its close cousin, the White-letter Hairstreak. This species was first discovered in the British Isles in 1828 when a Mr. Seaman, an entomological dealer, collected specimens from one of the most famous sites for this species - Monk's Wood in Cambridgeshire. These were thought to be specimens of the White-letter Hairstreak until Edward Newman, a Victorian entomologist of note, declared them to be Black Hairstreak.
This butterfly is not a great wanderer and an entire colony will often confine itself to a single area within a wood, despite there being suitable habitat nearby. The inability to colonise new areas at a pace in balance with habitat loss may partially explain the scarcity of this species. This butterfly has a very restricted distribution that follows a line of clays between Oxfordshire in the south-west and Cambridgeshire in the north-east.
This species was first defined in Linnaeus (1758) as shown here (type locality: Not stated).
The status of the Black Hairstreak is considered stable, although the future of this fragile butterfly is dependent on appropriate protection and habitat management.
|Species of Conservation Concern|
The table above shows the distribution and population trends of species regularly found in the British Isles. The distribution trend represents a comparison between data for the periods 1995-1999 and 2005-2009. The information provided is taken from the Butterfly Conservation report The State of the UK's Butterflies 2011. The UK BAP status is taken from the UK Biodiversity Action Plan (UK BAP) (2007 review).
Black Hairstreak colonies are typically located in small woods or nearby hedgerows, where Blackthorn, the larval foodplant grows. Wild Plum is also used occasionally. Sites are located in sheltered but sunny positions and typically have a southerly aspect to them.
Click here to see the distribution of this species or here to see the distribution of this species together with specific site information overlaid. Alternatively, select one of the sites listed below.
|Asham Meads, Bernwood Forest, Bernwood Meadows, Brampton Wood, Finemere Wood, Glapthorne Cow Pasture, Howe Park Wood, Marston Thrift, Monk's Wood, Oxford Lane, Piddington Wood, Rushbeds Wood, Salcey Forest, Whitecross Green Wood|
This butterfly has an extremely short flight period, being seen in the last 2 weeks of June and the first week of July. There is a single generation each year.
The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.
The adults spend much of their time resting high up on Maple, Ash or the larval foodplant, Blackthorn, crawling over leaves and twigs, in search of aphid honeydew from which they feed - making it extremely frustrating to get a sighting of this species. However, they will come down to feed on various nectar sources, Privet and Bramble flowers being particular favourites.
When active, the butterflies are extremely difficult to follow in flight - a characteristic of all hairstreaks. To make matters worse, the Black Hairstreak is often found in the company of both White-letter and Purple Hairstreaks and distinguishing these three species in flight is almost impossible. The butterfly always settles with wings closed and regulates its temperature by positioning its wings at an appropriate angle to the sun.
When engaged in courtship, male and female whirl around each other in a tireless dance which lasts for several minutes, ultimately resulting in the pair mating.
Adults feed primarily on Honeydew / Sap. Bramble (Rubus fruticosus), Buttercups (Ranunculus spp.), Hogweed / Angelica (Umbelliferae) and Privet (Ligustrum vulgare) are also used.
Eggs are laid singly in the forks of small twigs of the foodplant, usually on a rough patch. The egg is blue-green when first laid, but gradually turns dark brown, ultimately becoming a pale grey with the onset of winter and often becomes discoloured due to algae which have formed on it. The larva is fully-formed within the egg as it passes the winter.
The egg hatches in spring, without eating the eggshell, the newly-emerged larva sits on a flower bud which it proceeds to eat, making good use of its extensible neck. More-mature larvae rest on the leaves of the foodplant, eating the tenderest leaves.
Although the appearance of the larva changes as it matures, it is always well-camouflaged and always matching the flower buds or leaves on which it feeds. The larva feeds during the day and has 3 moults in total.
The primary larval foodplant is Blackthorn (Prunus spinosa). Wild Plum (Prunus domestica) is also used.
The pupa is superbly camouflaged as a bird dropping and is quite visible to the trained eye, attached to the upper surface of a leaf or twig. The pupal stage lasts around 3 weeks.
Description to be completed.
Click here to see a full list of aberrations for this species.
Both Black Hairstreak and White-letter Hairstreak are very local species, but do fly together on rare occasions. There are two features that distinguish these species. The first 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, that is absent in the White-letter Hairstreak. The second is that the White-letter Hairstreak has a more pronounced white line on its hindwing, forming a letter "W" from which the White-letter Hairstreak gets its name. This line is less prominent in the Black Hairstreak.
Black Hairstreak (left) and White-letter Hairstreak (right)
The following links provide additional information on this butterfly.
The species description provided here references the following publications:
|Butler (1869)|| Butler, A.G. (1869) Catalogue of diurnal Lepidoptera described by Fabricius in the collection of the British museum.|
|Doubleday (1847)|| Doubleday, E. (1847) List of the Specimens of Lepidopterous Insects in the Collection of the British Museum.|
|Leach (1815)|| Leach (1815) In Brewster: The Edinburgh Encyclopaedia.|
|Linnaeus (1758)|| Linnaeus, C. (1758) Systema Naturae. Edition 10.|
|Scudder (1876)|| Scudder, S.H. (1876) Bulletin of the Buffalo Society of Natural Sciences.|