Butterflies of
Britain & Europe
Silver-washed
Fritillary
Argynnis paphia
LINNAEUS, 1758
Family - NYMPHALINAE
subfamily -
HELICONIINAE
Tribe - ARGYNNINI
introduction
|
habitats |
lifecycle |
adult behaviour
Silver-washed Fritillary
Argynnis paphia, male, Wiltshire, England
Introduction
The Silver-washed
Fritillary is one of Europe's largest and most magnificent
butterflies. The male, illustrated above is easily distinguished
from the female by the 4 prominent horizontal dark streaks on it's forewings. These
contain androconial scales, from which pheromones are
released during the courtship flight.
Silver-washed Fritillary
Argynnis paphia, female, Wiltshire, England
Females have a similar
pattern of black spots, but lack the horizontal streaks. They
are normally a dull golden colour, often with a slight bronzy
tinge.
The greyish female illustrated below is the scarcer
and very beautiful form known as
valesina.
This variety is recessive. It only occurs at a few sites,
usually in long established colonies in oak forests. Captive
breeding experiments have proven that about 10% of
females in Hampshire, Wiltshire and Dorset are of the
valesina variety, but the numbers
actually observed in the wild are considerably lower as they are
more secretive in behaviour than normal females, and tend to
inhabit shadier parts of the forest.
Silver-washed Fritillary
Argynnis paphia, female form
valesina
The butterfly is
common and widely distributed across much of Europe, but absent
from northern Scandinavia, northern Britain, and the southern
parts of the Iberian peninsula. Beyond Europe it occurs in
northern Algeria, and is widespread across temperate
Asia to China, Korea and Japan.
Silver-washed Fritillary
Argynnis paphia, male, Alice Holt
forest, Hampshire, England
The common name refers
to the suffused silvery markings on the greenish underside
hindwings. These features distinguish this species from
the European
Pandoriana pandora,
in which these markings are much more clearly defined.
Another similar
species is
Childrena zenobia,
from China, Siberia and Tibet, which has a conspicuous
lattice of silver markings on the underside hindwings.
Argyronome ruslana
from Korea, Siberia and Japan is also very similar to
Argynnis paphia
on the upperside, but it's underside hindwings have a broken
silver median line dividing the greenish basal area from the
reddish outer half of the wings.
Silver-washed Fritillary
Argynnis paphia, males basking on
bracken in early morning
Habitats
The
Silver-washed Fritillary prefers slightly shadier conditions than most other woodland
Fritillaries and is better able to survive in high canopy forests and woods that have become neglected and overgrown. The highest populations occur in
mature oak and beech plantations where a program of regular thinning encourages a profusion of dog
violets to germinate beneath the trees. The best sites are also typified by
having glades and grassy tracks where thistles, brambles and other nectar sources
are abundant.
The butterfly is a powerful flyer
and quite mobile, being often found on scrubby downland or along hedgerows or
railway cuttings where these habitats are close to its woodland homelands. Thus
it is able to recolonise neglected woods which have been returned to coppice
management and once again become suitable as breeding sites.
In the early 19th century this
species was found as far north as Dumfries, but has always been very scarce in
northern Britain, and has been extinct in Scotland for about 150 years. There
was however a freak migration in 1910, when the species found its way as north
as Aberdeen. The butterfly is still very rare north of a line running from
Liverpool to Peterborough, but has recently shown signs of expansion, probably
as a result of climate change. In 2009 for example I found a fresh male
Silver-washed Fritillary visiting bramble blossom in a wood near Witherslack in
Cumbria.
Silver-washed
Fritillary
Argynnis paphia, males at bramble, Hampshire, England
Lifecycle
The
butterflies emerge in June and July and have a life expectancy of about 3-4
weeks, although many are killed by birds before fulfilling their potential life
spans.
The
greenish-white eggs are laid singly in crevices in the bark of oaks, and more rarely on other
trees including beech, ash and larch; normally at a height of about 2 metres, on the moss-covered
east or north-facing side of the trees. The trees chosen tend to be about 50-100
year old specimens growing along the edges of rides, and illuminated by dappled
sunlight. Often a female will revisit the same favoured
tree trunk, laying a dozen or more eggs in the space of an afternoon.
Immediately after hatching in August, the tiny caterpillars
eat their egg-shells, which
contain vital nutrients. They then attach themselves to a little pad of silk
which they spin on the tree trunk, and enter a state of diapause, remaining hidden in
a chink in the bark until the arrival of sunny weather in March of the
following year. They then descend the trees and wander in search of dog
violets Viola riviniana.
They feed diurnally, eating only the lobes of the violet leaves, and then
move on to another plant.
The fully grown larvae can
sometimes be found basking on dead oak leaves in May or early June. They are
black, with a double yellow line along the back, and adorned with dull orange
branched spikes on the back and sides. The 2 spikes on the first segment are
black, and inclined forward over the head.
The
slightly spiky pupa is mottled in shades of brown, and decorated with golden spots.
It is almost impossible to find in the wild, but is reportedly suspended by the cremaster from
the woody stems of bushes, or from twigs on oak trees. The pupal stage lasts for
about 3 weeks.
Silver-washed Fritillary
Argynnis paphia, male, Wiltshire, England
Silver-washed
Fritillary
Argynnis paphia, Hampshire
( image
© Colin Baker )
Silver-washed
Fritillary
Argynnis paphia, Wiltshire
Adult behaviour
The first males emerge in late June, appearing about a week before the first females.
Individuals can live for up to a month, with worn
specimens seen as late as early September.
Overnight, and during dull weather,
the butterflies roost amongst oak leaves high in the tree tops. In
the early morning they bask high up until the rays of the sun
reach the forest floor, and then drift down to continue basking on
bracken, hazel leaves, and other low vegetation.
Silver-washed Fritillary
Argynnis paphia, males, Wiltshire, England
As the day warms
up they become more active, nectaring avidly at thistles, bramble
blossom, lime blossom, hemp agrimony, hogweed and ragwort. They are also often seen
imbibing honey-dew from the surface of leaves, or settling on
stony tracks to obtain mineral-rich moisture.
The courtship ritual of the
Silver-washed Fritillary is one of the most endearing and familiar
sights of the English summer. The female flies in a straight line
along woodland tracks at a height of about 2 metres, and as she
does so she emits an aphrodisiac scent from the tip of her
abdomen. The male responds by following her closely,
repeatedly looping under and over her, and showering her with pheromones
released from the 4 black bars of androconial scales which run
along the veins of his forewings.
In many cases this tantalising display fails to entice the female
into mating, but if she is receptive she leads the male to a clump
of leaves high in an oak tree where copulation takes place. Periodically the pair fly
down to settle on bracken or hazel, or to nectar at bramble, but
return to the tree tops if disturbed. Copulation lasts about 2
hours and takes place in late morning or early afternoon.
Silver-washed Fritillary
Argynnis paphia, male, Wiltshire, England
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