This handsome butterfly is widely distributed throughout southern areas wherever there are oak trees; even a solitary tree may support a colony. It is frequently overlooked as adults remain largely in the canopy where the main adult food source is honeydew; tsecreted by aphids and jealously guard this lofty teritory , and can even attack other competitors such as wasps they fly more commonly in the evening of a warm summer's day. They are only driven down to seek fluid and nectar during prolonged drought, as occurred in 1995-6. The Purple is seen more in the male than in the female . The silvery -grey underside with its tails , shows a watermark appearance behind the hairstreak line
There has been a recent increase in records and an extension of the range of this butterfly especially in the English Midlands and south-west Scotland, even in urban areas (including London) which may be related to improvements in atmospheric quality.
IMAGING COURTESY OF STEVE SHROUD (C)
Resident Range expanding in Britain.
UK BAP status: not listed
Butterfly Conservation priority: low
European threat status: not threatened
Protected in Northern Ireland
The Purple Hairstreak occurs from North Africa to Southern Scandinavia and across central Europe to Asia Minor. It is stable throughout much of Europe but has declined in several countries and is spreading at the northern edge of its range.
The Purple Hairstreak is restricted to oak trees including both the native species, Sessile Oak (Quercus petraea) and Pedunculate Oak (Q. robur), and the introduced Turkey Oak (Q. cerris). Evergreen Oak (Q. ilex) also may be used.
Colonies of Purple Hairstreak may be found in woodlands where sufficient oaks remain, in ancient park woodlands, associated with hedgerow and lane-side oaks, on heathland oak scrub, oak screens along the edge of conifer plantations, and even in towns including central London.
In groups of oaks, there is usually a favourite tree and isolated oaks (which may be survivors from when the site was more heavily wooded) may support colonies that have become self-contained on the same tree for many years.
In Ireland, the butterfly tends to prefer small oaks and colonies are often small. Adults will perch and feed on Ash and elms in regenerating woodland because they are fast growing and out-top oak, but oak is needed for breeding.
With wings closed, 15-20 mm
Males have an almost black upper surface to the wings, which shimmer an iridescent deep purple as they catch the sun. The undersides of the wings are a pale silvery grey with an irregular, wavy, white line extending across them. The hind wing has an orange streak towards its outer edge and there is an orange spot with a black pupil towards the bottom corner which has a small black and white tail.
Females are very similar to the males but the characteristic iridescent purple patches are restricted to the bases of the forewings only.
Behaviour and life history
The Purple Hairstreak forms colonies and spends most of its life in the canopies of oak trees but does, on occasion, come down into the lower canopy and surrounds to feed on flowers. It spends most of its time perched high up in the canopy, periodically leaving its post in a dancing flight above the canopy. This butterfly overwinters as an egg with the young caterpillars emerging in late March and pupating at the beginning of June. Adults emerge five or six weeks later to mate and lay their eggs on oak leaves on which the caterpillars feed.
Where to look for it
It is a very elusive butterfly which usually only reveals itself after a long and patient search of oak canopies. It is most likely to be found around oak trees in woodland situations but, in Plymouth, it is most easily and frequently observed associated with oaks growing in hedgerows.