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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
Butterflies of Britain & Europe
 
Purple Hairstreak
Quercusia quercus LINNAEUS, 1758
Family - LYCAENIDAE
subfamily - THECLINAE
Tribe - EUMAEINI
 
 introduction | habitats | lifecycle | adult behaviour
 
Quercusia quercus, female resting on oak leaf, Hampshire, England
 
Introduction
 
The Purple Hairstreak is a very widespread species occurring throughout Europe with the exception of northern Scotland and northern Scandinavia. It's range extends across the Middle East and temperate Asia as far as the Ural mountains and Kazakhstan, and it also occurs in Morocco and Algeria.
 

In southern Britain the Purple Hairstreak is a very common species, although it's semi-crepuscular nature and habit of spending most of it's time high in tree tops can create the illusion that it is scarcer. The true abundance of the butterfly can be illustrated as follows :

Between 7.00-7.30pm on 2nd July 2008, during a walk around Whiteley Pastures in Hampshire I counted 173 Purple Hairstreaks in flight around the tops of oak trees. The mature broad-crowned oaks produced the highest counts, with between 8 - 12 seen in flight above each tree, while the smaller and more spindly trees typically hosted at least 3 or 4 specimens. These figures only represent butterflies seen in flight, and it can be safely assumed that for each specimen in flight there must have been at least another 3 or 4 at rest which escaped detection. During the limited time available I was only able to look at about 0·5% of the oaks in the wood ( i.e. those along a half-mile stretch of one particular track ). If my mathematics are correct this means the total population of Purple Hairstreaks at Whiteley Pastures on that particular day was possibly in excess of 103,800 butterflies ( multiply 173 x 3 to get an estimate of butterflies along the section of track that I visited, and multiply that figure by 200 to include the total number of oaks in the wood ).
 
The only other European butterfly which could be confused with this species is the Spanish Hairstreak Laeosopis roboris, which is found only in Spain, Portugal and the south of France. It is similar in appearance on the upperside, but the underside is different, lacking the white "hairstreak" line, and having a prominent band of orange, white and black submarginal spots.
 
Quercusia quercus, female, Surrey, England
 
Habitats
 
In Europe and north Africa the Purple Hairstreak breeds almost anywhere that oaks grow, even in hot arid scrubland bordering the Mediterranean.
 
In Britain it is found primarily in southern and central England, and throughout Wales. It also occurs in widely scattered colonies in northern England, in the Scottish Highlands, and in Ireland.
 
Heavily wooded areas often have enormous populations of this butterfly. I have also found a few colonies on isolated stands of oak on heathland in the New Forest, and in suburban parks, although these are likely to be relict populations.
 
Quercusia quercus, male, Surrey, England
 
Lifecycle
 
Purple Hairstreaks are single brooded throughout their range, but have a protracted emergence beginning in late June, and lasting well into August.
 
They lay their eggs singly, or sometimes in two's and three's, on the terminal buds and twigs of oaks. The butterflies lay at all heights on the trees, but young bushy growth on the crown or the south side of the trees is heavily favoured.
 
Following the Great Storm of October 1987, which felled thousands of trees throughout southern England, I examined several hundred fallen oaks in Hampshire and West Sussex, and found that eggs were present on about 95 percent of the English ( pedunculate ) oaks Quercus robur that I examined. Less than 5 percent of the sessile oaks Q. petraea held eggs, and none were found on red oak Q. rubra, turkey oak Q. cerris,  or holm oak Q. ilex, although this latter species is certainly used in southern Europe. I also examined many specimens of sweet chestnut Castanea sativa, which is given as a foodplant in some early reference works, but found no evidence of the butterfly using that species.
 
Eggs were mainly laid on trees along woodland edges, or bordering forest tracks. Mature oak standards in hazel or sweet chestnut coppice were also frequently used. Hedgerow oaks are less commonly used.
 
The greyish eggs over-winter, and hatch in late March and early April, when the buds begin to open.
 
Quercusia quercus, fully grown caterpillar feeding on oak
 
The young larvae burrow into the leaf buds to feed, but when older they spin a thin web of silk around a clump of leaves, resting within it by day, and emerging at night to feed. The fully grown larva is plump, with a pair of raised humps on each segment. It rests at the base of leaf clumps, and frequently has ants in attendance.
 
Ants, particularly Lasius niger, also attend the chrysalis, which is formed on the ground, and inadvertently protect it from attack by parasitoids and small predators. The ants usually cover the chrysalis to hide it, or transport it into their nests at the base of oak trees.
 
The adult butterflies emerge in the early morning, and can sometimes then be seen basking in groups on the ground or on foliage beneath oaks.
 
Adult behaviour

 

The butterflies are sedentary in nature, and normally only seen when small groups of them flutter around the tops of oaks in the late afternoon, presumably indulging in mate location and courtship. When seen in flight the butterflies appear silvery, like spinning coins.

 

During the rest of the day they tend to sit motionless, perched on foliage in the canopy, resting or feeding on the sugary secretions of the oak aphid Phylloxera quercus, which coat the upper surface of the oak leaves. This secretion, known as "honey dew" is undoubtedly the major source of sustenance for adults of both sexes.

 

I have occasionally found adults nectaring at hogweed or bramble flowers, or imbibing mineral-rich moisture from mud or gravel tracks, and have also found them many times at rest on bracken beneath oaks, presumably having emerged from the ground, and crawled up the bracken stems to hang and dry their wings.

 

On blustery days Purple Hairstreaks occasionally get blown down from the trees, and can then be found amongst grasses and low growing plants.

 

Particular trees within a wood tend to attract aggregations of adults, which can be seen flying across forest tracks from other oaks. These assemblies are probably related to courtship behaviour, as in the case of Purple Emperors and various other species.

 
                                                       
Almost every British and European species of butterfly is declining rapidly in numbers, due in most cases to loss or degradation of habitats.
 
You can help to reverse the decline by supporting conservation organisations which purchase and manage habitats as nature reserves, and which lobby government at local, national and international levels, often very successfully, to bring about changes in farming, forestry and urban development policies.
 
Please contact the conservation organisations for advice on how you can help protect British and European butterflies and their habitats. You may be able to offer practical help e.g. by monitoring butterfly populations or helping to manage nature reserves. Donations to these organisations enable them to employ ecologists and biologists. Even if you are unable to provide such help, merely having your name on the membership list can be a powerful tool for conservation organisations wishing to demonstrate the levels of support they have for their policies.

 

 
Text and photographs protected by Copyright © Adrian Hoskins 2007-2008, and must not be reproduced or published in part or in whole elsewhere in any form without written permission from Adrian Hoskins. Breach of copyright will be pursued by litigation.
 
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