Butterflies of
Britain & Europe
Glanville Fritillary
Melitaea cinxia
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
NYMPHALINAE
Tribe - MELITAEINI
subtribe -
EUPHAEDRYINA
introduction
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habitats |
lifecycle |
adult behaviour
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Glanville Fritillary
Melitaea cinxia, male, Hampshire
coast, England |
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Glanville Fritillary
Melitaea cinxia, male, Wheelers
Bay, Isle of Wight, England |
Introduction
The
Glanville Fritillary is named after Eleanor Glanville, who originally discovered
the butterfly in the 18th century, at a woodland in Lincolnshire. There is a
famous story that Lady Glanville's will was contested on the grounds that she
must be guilty of "Acts of Lunacy" because only someone who was "deprived of her
senses" would "go in pursuit of butterflies" !
This piece of
history serves to demonstrate a very strange misconception regarding naturalists
in the past. It is also a stark reminder of how much more widespread and
abundant butterflies were before the Industrial Revolution destroyed the British
landscape. A cooling climate also probably contributed to the decline of this
species, as its range gradually contracted further and further southwards. At
the middle of the 19th century it was still common along the Kent coast, but by
the beginning of the 20th century it had become restricted to a handful of sites
along the south coast of the Isle of Wight - the only part of Britain where it
breeds naturally today.
Abroad it occurs
across most of mainland Europe, with the
exception of Portugal, central / southern Spain, and northern Scandinavia. It
is also found in the Atlas mountains of Morocco, and in temperate Asia from the
middle east to Mongolia.
There are no other similar species in Britain, but in Europe it can be
confused with the Knapweed Fritillary
Melitaea phoebe,
which is a widespread species, or with Freyer's Fritillary Melitaea arduinna,
which is a local species restricted to south-east Europe.
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Glanville
Fritillary
Melitaea cinxia, male, Hampshire |
Habitats
In Europe the Glanville
Fritillary
is found in a wide range of habitats including woodland glades, sub-alpine
meadows, field edges, and open grassland.
In Britain it is at the edge
of it's range and is only able to survive at a handful of particularly warm
sites along the south coast of the Isle of Wight. The critical factor is
probably the amount of sunlight which sites receive in late winter and early
spring when the caterpillars awaken from hibernation - the Isle of Wight
receives more hours per day of sunlight at this time of year than elsewhere.
The butterfly
breeds primarily on severely eroded sandstone undercliffs, where the larval
foodplant ribwort plantain grows in profusion, and where the extensive areas of exposed
ground create a very warm micro-climate. Most sites only support colonies for a
few years because they soon become overgrown, lowering the micro-climate until
it
eventually becomes too cool for the species. Luckily regular
land slippages create new areas of habitat which the butterfly can colonise, and
the status of the butterfly on Wight remains fairly stable. Sea defence constructions and tourist developments
do nevertheless threaten to destroy several of the butterfly's breeding sites.
Away from the coast the butterfly also breeds periodically on the
chalk grassland hillsides on the southern half of the island, but these colonies
tend to last only a year or two.
Occasionally temporary colonies become established on mainland
Britain, e.g. at Hordle Cliffs and Hurst Castle. They typically flourish for 2
or 3 years, but then disappear. They are almost certainly the progeny of single females which
periodically find their way across the Solent, so the genetic diversity
of each colony is minimal. After a few generations
genetic entropy weakens the stock, reducing the viability of the colony, and rendering
it
prone to extinction.
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Glanville Fritillary
Melitaea cinxia, male, Hampshire |
Lifecycle
In warmer parts of Europe the
butterfly is double brooded, but in Britain there is usually only a single
generation of adults. These normally begin to emerge in mid-May and
remain flying until mid-June, but in exceptionally warm years
the butterflies can appear at the end of April, and
only remain on the wing until late May. In such years there may
be a partial 2nd brood, emerging in August.
The eggs are yellow, and laid in
batches of up to 200 on the underside of leaves of ribwort
plantain
Plantago lanceolata, where it grows
in sheltered depressions or crevices.
A wider range of plants is used in Europe, including various
other
Plantago
species, plus
Centaurea
and
Veronica. Usually the entire batch is laid at once, a process
that may take 2 days, but sometimes the females lay smaller
batches of only about 50 eggs, on plants at different parts of
the breeding site. The eggs hatch after about 10 days, in late
May.
The larvae are black and
spiky with reddish-brown heads. They feed gregariously and bask on
silk webs which they spin over plantains. In September, when in
the 3rd or 4th instar, they
leave the plantains, and spin a dense web amongst tall grasses.
There they hibernate until early March. Upon awakening they feed in swarms which march across the undercliffs
consuming every plantain they encounter. Often large numbers of
the larvae can be seen wandering on footpaths, but fortunately
most seem to avoid being crushed.
If the supply of ribwort plantain becomes exhausted the larvae will
switch to buck's horn plantain
P. coronopus,
but contrary to early entomological literature they do not
utilise sea plantain
P. maritima.
In April, when almost
fully grown, they become more solitary. The rate of growth
varies from one larva to another, with the result that there are
usually still many larvae around in May when the first male
butterflies emerge.
The pupae are greyish, marked on
the abdomen with bands of small orange and black spots. They hang by the cremaster from
grass stems, roots, or stones. Normally they pupate singly, but
clusters of 4 or 5 are sometimes found in crevices. The pupal
stage lasts about 2 weeks.
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Glanville
Fritillary
Melitaea cinxia, male, Hampshire |
Adult behaviour
The
butterflies have a rapid whirring flight, usually close to the ground, and
rarely fly more than a few metres at a time. Periodically they settle
to bask on low foliage or bare ground. They also often settle with
wings closed, amongst pebble or on the flower heads of plantain,
sea purslane or thrift. There are few experiences more enchanting
than watching a group of Glanville Fritillaries at rest on the
pink flowers of thrift, swaying gently in the breeze, with the
sound of waves lapping the shore.
Males
patrol irregular beats across the breeding sites, and intercept
all other Glanville Fritillaries of either sex. If a male meets a
female that has already mated, she settles amongst low grasses,
flutters her wings rapidly, and slightly raises her abdomen as a
rejection signal. If the male persists, she then closes her wings
and remains completely still until the male loses interest and
flies away. When a male encounters a virgin female copulation
takes place almost immediately without any preliminary courtship
ritual, and the pair remain copulated overnight.
Typical breeding
sites have a wide range of potential nectar sources including
thyme, sea purslane, sea kale, red clover and birds foot trefoil, but the butterflies
ignore most of these in favour of thrift, hawkweeds, buttercups,
kidney vetch and red valerian.
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Glanville Fritillary
Melitaea cinxia, male, Hampshire |
During periods of
dry weather the butterflies roost overnight on the flowerheads of
thrift, sea purslane or plantain, but when there is a threat of rain they go
deep into grass tussocks, clumps of horsetail or other vegetation,
or hide in crevices in the undercliffs.
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