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Butterflies of
Britain & Europe
Green Hairstreak
Callophrys rubi
LINNAEUS, 1758
Family - LYCAENIDAE
subfamily -
THECLINAE
Tribe - EUMAEINI
introduction
|
habitats |
lifecycle |
adult behaviour
Text and images protected by Copyright © Adrian
Hoskins 2007-2008, ( unless stated otherwise ) and must not be reproduced or published in part
or in whole elsewhere in any form without written permission from
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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.
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