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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.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
 
Green Hairstreak
Callophrys rubi LINNAEUS, 1758
Family - LYCAENIDAE
subfamily - THECLINAE
Tribe - EUMAEINI
 
 introduction | habitats | lifecycle | adult behaviour
 
Green Hairstreak Callophrys rubi, male, Purbeck Hills, Dorset, England
 
Introduction
 
The Green Hairstreak never displays it's brown upperside except when in flight. The green colour of the underside ( and the blues and coppers of other Lycaenids ), is produced by light refracting and reflecting from a microscopic lattice within translucent wing scales. The colours are iridescent - varying in hue according to the directional qualities of the light and angle of view. The Green Hairstreak can thus appear to be metallic apple-green, turquoise or emerald, when viewed from various angles.
 
Green Hairstreak Callophrys rubi, female, Dorset, England
 
Some individuals have plain undersides, but on others, the hindwings are marked with a row of white dots. The sexes are almost identical, but the male has a patch of scent scales in the discal cell of the upperside forewing. This is also visible in the form of a small raised pad in the cell on the underside, as shown in the photograph below.
 
Green Hairstreak Callophrys rubi, male, Hampshire, England
 
The butterfly is widely distributed in Europe, all the way from the Mediterranean islands to the far north of Norway and Sweden. It also occurs in Morocco and Algeria, and in most of temperate Asia. There are numerous closely related species elsewhere in the world, including the unfortunately named Sad Green Hairstreak Cyanophrys miserabilis of North America, and several Amazonian species.
 
In southern France, Spain, Portugal, Morocco and Algeria it can be confused with the similar Chapman's Green Hairstreak Callophrys avis, which occurs in dry scrubby areas and feeds as a larva on Arbutus. They can be separated by examination of the eye borders, which in rubi are white, but in avis are reddish. The white dotted line on the underside hindwings is placed centrally in avis, but in the post-discal area in rubi.
 
Habitats
 
The Green Hairstreak occurs throughout most of the British Isles, but is quite localised, being mainly found on scrubby hillsides or warm sheltered valley bottoms. In southern counties of England it particularly favours the lower slopes of south-facing grassy hillsides where there are hedgerows of hawthorn, blackthorn, bramble, elder or gorse.
 
South facing chalk grassland slopes like this are ideal habitats for the Green Hairstreak.
 
It also occurs in lesser numbers along disused railway cuttings, in woodland clearings, old chalk quarries, and on dry heathlands. In northern Britain the butterfly is found, sometimes in large numbers, on moors, sphagnum bogs and wet lowland heaths. There are also many small colonies around the northern shores of Scottish lochs.
 
Lifecycle
 
The butterflies emerge in early April in forward seasons, but may be delayed until mid May in cool wet springs. They normally remain on the wing until early June.
 
Females roam widely over their habitat, laying their eggs singly on the leaves or flower buds of the various foodplants, including bird's foot trefoil Lotus corniculatus, common rockrose Helianthemum chamaecistus, dogwood Cornus sanguinea, buckthorn Rhamnus catharticus, gorse Ulex europaeus, and bilberry Vaccinium myrtillus.
 
At Levin Down in Sussex, I watched a particular female ovipositing over a half hour period on a hot sunny morning in May 2006. It flew back and forth, covering an area of about 20 x 50 metres, carefully selecting each egg-laying site, always choosing to lay on leaves of rockrose, although bird's foot trefoil and other known foodplants were present.
 
In April 2007 at Magdalen Hill Down, I watched another female behave in a similar manner, depositing her pale green eggs meticulously onto the upper surface of rock rose leaves, at the point where the base of the leaves emerges from the stems. At both sites the eggs were laid on plants growing on ant-hills. This is probably because ant-hills tend to be warmer than surrounding areas, but could also be influenced by an association between the larva and ants - many Lycaenid larvae are "milked" by ants, which drink a sweet secretion produced from a "honey gland" on the back of the larva.
 
Green Hairstreak Callophrys rubi, female ovipositing on common rockrose
 
Like other Lycaenid larvae, that of the Green Hairstreak is plump, like a woodlouse. It is green, and marked with rows of yellow dots on the back and sides. The larva feeds on the flower buds, flowers or tender young leaves of common rockrose, gorse, bilberry, bird's foot trefoil, dogwood, broom and various vetches. At some sites the larvae feed on buckthorn berries, in which they make a hole through which they extract the contents.
 
The larva leaves the foodplant to pupate just under the surface of the ground, often where there are stones or fallen leaves. The pupa is attractive to ants, and has the ability to produce a rasping noise if disturbed, presumably as a defence mechanism.
 
Adult behaviour

 

The flight period is from early April until early June at the warmest sites; or from early May until late June at cooler or northern sites.

 

Green Hairstreak Callophrys rubi, male, Purbeck Hills, Dorset

 

The males and females behave quite differently. Males establish territories, perching on gorse flowers, or on the foliage of hawthorn, blackthorn, elder, privet and various other bushes, often at the bottom of hills. On sunny mornings they use these perches as vantage points, and will dart up and intercept other small insects, including bees, flies, and various butterfly species, as well as other Green Hairstreaks.

 

Often 3 or 4 males will have overlapping territories, so male-male encounters are very frequent. When 2 males meet, they engage in a frenzied battle, zipping about in tight circles, each trying to outwit and out manoeuvre the other with constant changes of direction. These battles often last well over a minute, during which the duo will fly high above bushes and up to 5 metres horizontally from the point where the conflict began. Eventually one male gives up, at which point each returns to it's original perch, or to another nearby leaf.

 

Green Hairstreak Callophrys rubi, female, Dorset, England
 
I have not observed courtship, but it is likely that the sexes copulate without any pre-nuptial ritual. I have occasionally found copulated pairs settled on low herbage, but they are difficult to detect due to the very effective cryptic colouration.

 

Females spend most of their time fluttering inconspicuously just above the ground in search of egg-laying sites, and are seen far less often than the males.

 

Both sexes nectar at a wide range of spring flowers including bird's foot trefoil, horseshoe vetch, common vetch, gorse, common rock rose, elder, holly, wayfaring tree, bluebells, cowslip, wood forget-me-not, dandelion, daisy and hawthorn. 

 

Green Hairstreak Callophrys rubi, female, Dorset, England
 
In Dorset I have observed Green Hairstreaks flying around elms and field maples at the bottom of chalk hills in late afternoon, and settling for long periods on ivy foliage on the higher branches of small oaks, but have not been able to determine whether both sexes indulge in this activity.
 
                                                       
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.

 

 
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