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%20Rowland%20Wood-%20NKemp001a.jpg "Purple Hairstreak 1")
Purple Hairstreak Quercusia quercus female, Rowland Wood, East Sussex – Nigel Kemp
Introduction
The Purple Hairstreak is a very widespread species occurring throughout Europe with the exception of northern Scotland, northern Sweden and Norway. It’s range extends across the Middle East and temperate Asia as far as the Ural mountains and Kazakhstan. It also occurs in Morocco and Algeria.
| In southern England the Purple Hairstreak is a very common butterfly but its semi-crepuscular nature and its habit of spending most of its 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 logic is 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 mature oaks in the wood ). |
The only other European butterfly which could be confused with quercus is the Spanish Hairstreak Laeosopis roboris, which is found only in Spain, Portugal and southern France. It is similar on the upperside, but the underside lacks the white hairstreak line, and has a prominent band of orange, white and black submarginal spots.
Purple Hairstreak Quercusia quercus, Fermyn Wood, Northamptonshire – Adrian Hoskins
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.
Lifecycle
Purple Hairstreaks are single brooded throughout their range, but have a protracted emergence beginning in late June, and lasting well into August.
The eggs are laid singly on the terminal buds and twigs of oaks. Sometimes 3 or more eggs can be found together on a single bud, but these are usually the result of repeat visits by a single female, rather than having all been laid at the same time. The butterflies oviposit at all heights on the trees, but young bushy growth on the crown or the south side of the trees is heavily favoured. In a study carried out in 1987, I examined several hundred wind-felled oaks in Hampshire and West Sussex. I found that eggs were present on about 95 percent of the English oaks Quercus robur examined, but less than 5 percent of the sessile oaks Q. petraea held eggs, and none at all 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. 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. Immediately after hatching the young larvae burrow into the leaf buds to feed, but when older they feed on the leaves. Each larva spins a thin web of silk around a clump of leaves, resting within it by day, and emerging at night to feed. When fully grown the larva is plump, and has 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 pupa, which is formed on the ground. The ants cover the chrysalis to hide it, or transport it into their nests at the base of oak trees. Inside the ant nest the pupa is protected from predators.
The adult butterflies emerge in the early morning, and can sometimes then be seen basking on the ground or on foliage beneath oaks.
Purple Hairstreak Quercusia quercus, Fermyn Wood, Northamptonshire – Adrian Hoskins
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, feeding on the sugary secretions of the oak aphid Phylloxera quercus, which coat the upper surface of the oak leaves. This secretion “honey dew” is undoubtedly the major source of sustenance for adults.
I have occasionally found adults nectaring at hogweed or bramble flowers, or imbibing mineral-rich moisture from mud or gravel tracks. I’ve 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.
Quercusia quercus, female resting on oak leaf, Havant Thicket, Hampshire – Adrian Hoskins