Butterflies of
Britain & Europe
Red Admiral
Vanessa atalanta
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
NYMPHALINAE
Tribe - NYMPHALINI
introduction
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habitats |
lifecycle |
adult behaviour
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Red Admiral
Vanessa atalanta, female,
Stansted Forest, West Sussex, England |
Introduction
The Red
Admiral is probably Britain's most well known butterfly, and certainly one of
the most beautiful, with it's almost perfect pattern of red bands and white
spots on a black background. It was first named as "the
Admirable" by Moses Harris in 1766.
The
butterfly is widely distributed and common throughout mainland Europe and north
Africa. In northern Scandinavia it is a regular migrant. In Britain its status
has changed over the years. Up to the end of the 19th century it was considered
to be a resident that hibernated as an adult butterfly. During the 20th century
it occurred as a migrant, although there were occasional years when a few adults
managed to survive the winter at sites along the south coast of England.
Recently there has been a further change in status. The butterfly can now be
seen flying regularly on sunny days even in mid winter in the southern counties
of Hampshire, Dorset and Sussex.
There is now
evidence also that larvae resulting from eggs laid in late autumn can
successfully overwinter and produce a new generation of adults in early spring.
The Red Admiral
cannot be confused with any other European butterfly except the similar
Indian Red Admiral Vanessa indica,
which has a much wider, irregularly shaped red band on the forewings. It occurs
together with atalanta
on Madeira and the Canary Islands, and throughout much of the Oriental region,
but is inexplicably absent from Europe and north Africa.
Elsewhere in the world there are several other Red Admiral species, including buana
from Sulawesi, samani
from Sumatra, dejeani
from Bali, and the very beautiful gonerilla from New
Zealand.
Habitats
This
Red Admiral occurs in Britain as a migrant originating from north Africa and
southern Europe, and being a highly mobile species, it
can turn up in any
habitat including woodlands, grasslands, meadows, heathlands and moors, coastal
habitats, riverbanks, low montane habitats, gardens, parks, allotments and town
centres. Males also gather at certain grassland hilltop sites, apparently to
intercept migrating females.
The number of migrants varies according to
climatic
conditions in Europe, and in turn this greatly affects the number of UK bred
butterflies seen later in the year.
Migrants
arriving in the early spring oviposit on stinging nettles growing alongside
hedgerows or in woodland glades, producing a summer brood in the UK which
typically emerges from mid July to early August. In early
autumn these
butterflies migrate south, arriving in southern woodlands
where they congregate to nectar at ivy blossom.
Red Admiral
Vanessa atalanta,
at ivy, Hampshire, England
There is now mounting evidence that
in mild winters a small percentage of Red Admirals
are able to
successfully over-winter in
southern England. They awake
on warm days, and
sightings are frequent in southern
woodlands on sunny days between October and
late January.
In
harsh winters Red Admirals
are usually killed by the hard
February frosts, but since
the turn of the 21st century the species has successfully overwintered in
significant numbers in many parts of southern England. In the
winter of 2006/2007 for example there were almost unbroken
sightings in West Sussex, Hampshire
and Dorset from October until the following March. The
surviving adults laid eggs as early as January, producing a new generation of
adults which emerged in early May.
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Red Admiral sightings in Stansted
Forest, winter 2006-2007 |
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Sept |
Oct |
Nov |
Dec |
Jan |
Feb |
Mar |
Apr |
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The chart above depicts the build up of Red Admirals following
southward migrations into Stansted Forest, 4 miles from the
English south coast on the Hampshire / West Sussex border;
and the rapid reduction in the population following the
gales, frosts and snow of late January & early February.
In early March most of the surviving Red Admirals
dispersed into the surrounding countryside. Their progeny emerged in May,
coinciding with the arrival of a new wave of immigrants from Europe.
On
9th November 2007, I counted a minimum of 12 Red Admirals in a small section of
Stansted Forest, but estimated that at least 150 must have been present in the
whole wood. Unfortunately, extremely wet and windy conditions prevailed over the
following few weeks, decimating the population. On 23rd December however, I
watched 2 Red Admirals basking on tree-trunks in the forest, despite having
endured 6 consecutive nights of severe ( minus 3°C ) frost the previous week.
At the end of January, in mild sunny conditions at least 3 Red Admirals were
flying in the forest, but cold and wet conditions persisted throughout the
spring, killing off the last survivors, and none were seen at Stansted after 9th
February.
|
Red Admiral sightings in Stansted
Forest, winter 2007-2008 |
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Sept |
Oct |
Nov |
Dec |
Jan |
Feb |
Mar |
Apr |
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Compared to the previous
winter, 2007-2008 was cooler, windier and considerably
wetter, with fewer sunny days. Frosts were minimal
prior to March, which produced many icy nights. April began
very cold, with snow, sleet and hail.
The harsh winter conditions had no negative impact on other
hibernating butterflies, with Peacock, Comma, Brimstone and
Small Tortoiseshell all being recorded in average numbers in
mid-late April.
The low number of Red Admirals arriving in autumn
2007 was mainly attributable to lower breeding success and
reduced immigration during the exceptionally cool and wet
summer. The maximum count was on 21st October when 17 were recorded nectaring at ivy flowers. Winter
survival rates were very low, with only one sighting
in March, and no more until 2 immaculate and extremely
active individuals were seen on 25th May. Their condition
and behaviour very strongly suggested they had emerged
locally within the previous couple of days - providing
fairly conclusive evidence that they were the progeny of
post-hibernation adults that had successfully over-wintered
at Stansted Forest.
Red Admiral
Vanessa atalanta,
Stansted Forest, West Sussex
Lifecycle
In late April
and early May, female Red Admirals can be observed flying around nettle
patches in woodland glades. They periodically alight on nettle
leaves Urtica dioica, upon which they lay a single egg. Usually a dozen or so
eggs will be laid on any sizeable nettle patch. Egg-laying is
interspersed with periods of basking and nectaring - typically at blackthorn, crab
apple, and wild cherry.
Second brood adults,
which may be of either UK or European origin, are less fussy
about oviposition sites. They will lay their eggs in any sheltered
sunny lowland habitat where the foodplant grows e.g. in July 2008
I watched 2 Red Admirals laying eggs on the
same small clump of unkempt nettles in my garden. Each laid about a dozen eggs
between about 11.00am and 1.00pm. The eggs were all laid singly on
the upperside of terminal nettle leaves. The egg-laying bouts,
which each lasted about 2-3 minutes were interspersed with periods
of basking, and periodic flights to nectar at a Buddleia bush a
few metres away. Interestingly a Comma was ovipositing
simultaneously on the same nettle patch, and neither species
seemed disturbed by the presence of the other.
The larva
lives within a tent of folded nettle leaves, spun
together with silk. Every few days, as the leaf-tent gets
devoured, the larva moves house, and spins a new tent nearby. If
the tent is opened, the spiky greenish-brown larva can be seen
within, normally curled in a J shape, head-downwards.
The
larvae of most butterfly species tend to wander away from their foodplants to pupate, but the Red Admiral
is unusual, forming it's greyish chrysalis within the
final leaf-tent.
Adult behaviour
|
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|
Red Admiral
Vanessa atalanta, basking on
larch trunk |
On sunny days the butterflies often bask on tree-trunks, always
assuming a head-downwards or sideways facing position. In warm but
overcast weather they like to bask on the foliage of bramble,
hazel and other bushes.
In early spring Red Admirals nectar at sallow catkins and
the blossom of blackthorn and hawthorn.
Favoured summer nectar sources include
dogwood,
hemp agrimony, bramble, marjoram, devil's
bit scabious, ragwort,
burdock, spear thistle
and ivy blossom.
They also
visit dung, or
imbibe mineral salts from damp ground, and
attend
sap runs on oak trunks.
In gardens they will
nectar at
Buddleia,
ice-plant and michaelmas daisies. In
orchards they will feed at fallen apples or pears.
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Habituation:
Red Admirals are
one of the more intelligent butterfly species - they
have the ability to habituate, i.e. to learn to react
less strongly to stimuli that prove to be harmless. Upon
entering their territory an intruder is immediately
investigated. In the case of human intruders a Red
Admiral will circle around several times, and will try
to ascertain whether the person poses a threat. If he or
she appears to be harmless the butterfly gets
progressively braver -
e.g.
I have on many occasions been
dive-bombed by individuals that have swooped to make contact
with the top of my head.
Once the butterfly has become habituated to the human
presence, the dive-bombing ceases, and the butterfly
behaves as if there was no one present. On the other
hand, if an intruder reacts to the butterfly by chasing
it, it becomes wary, and further chasing will be enough
to drive the butterfly out of the vicinity for several
minutes, even if there are attractants such as good
nectar sources available. |
Males are highly territorial, chasing after Commas and Peacocks as
well as other Red Admirals. When nectaring however they will
accept the presence of other species, and I have often seen mixed
groups of Red Admirals, Silver-washed Fritillaries, Commas, and
Large Whites gathered on a single flower head of hemp agrimony or
Buddleia.
|
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Red Admiral
Vanessa atalanta, nectaring at
hemp agrimony, Arnside Knott, Cumbria |
At night, on cold overcast days, and during the winter months, Red
Admirals roost head-downwards
on the trunks or lower branches of oaks, larches and other trees,
where the
bark-like underside of the wings provides
them with
excellent camouflage.
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Red Admiral
Vanessa atalanta, roosting on
larch trunk |
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