Purple Hairstreak, Quercusia quercus
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Identification
With wings closed, 15mm to 20mm.
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. Some of the best viewing sites in the city include Coombe Valley below Langley Plantation, the oaks besides the ponds at Efford Marsh Local Nature Reserve, the oaks on both sides of Forder Valley Local Nature Reserve and the oaks of Woodland Wood Local Nature Reserve by Canterbury Drive.
Distribution and status
Records would suggest that it is uncommon and very localised in its distribution in Plymouth. However, it is probably considerably more common than records would suggest.
When to look for it
Adults are on the wing during the second half of June and the first half of August.
Similar species
The combination of its colour-patterning and tree canopy habitat preference makes this species difficult to confuse with any other.