Britain & Europe
Family - NYMPHALIDAE
Tribe - APATURINI
Purple Emperor Apatura iris, male ©
Purple Emperor is undoubtedly the British butterfly most admired and
most sought after by butterfly watchers, breeders, photographers and
general naturalists alike. There are more stories told, and more
myths about this species than any other.
It is the second-largest
species in the UK ( the largest is the Swallowtail ),
measuring up to 85mm across the wings. The deep
purple-blue sheen on
the wings of the male is produced structurally, as light is
refracted by ridges on the wing scales. The colour is only visible from
certain angles, and under bright lighting conditions.
Less experienced butterfly watchers
often mistake the White
Admiral for this species. Both species are dark with white
banding, both fly around oaks, and both fly at the same time of year.
The White Admiral however
is smaller, far more graceful and delicate in flight,
has much more rounded wings, and lacks
the purple sheen.
In Europe the Purple Emperor
can be confused with it's slightly smaller relative
Apatura ilia, but that species
has an orange-ringed black spot near the outer margin of the
The Purple Emperor is distributed throughout much of
central Europe but is localised and scarce in southern France, Spain and
Portugal. It does not occur in Scandinavia, peninsula Italy or on
any of the
Mediterranean islands. Beyond Europe it's range extends across
temperate Asia from the Baltic states to north-east China and
Purple Emperor Apatura iris male ©
In Britain the
a breeding species in
most of the larger woodlands
southern and central
where the larval foodplant Salix grows along the edges of tracks.
once occurred over a wider area
but it is now more local. In Wiltshire,
Hampshire, Sussex and Surrey it occurs as a breeding
species in almost all of the larger woodland complexes. The
largest colonies are found in Rockingham Forest in
Northamptonshire. A handful of smaller isolated
colonies also occur in Herts, Oxfordshire,
Buckinghamshire, Lincolnshire, Somerset and Devon.
Most colonies comprise of less than 20
adults per day at peak season, although in the East Midlands up
to 30 can be seen in a single day under ideal conditions in
certain forests. Individuals butterflies have a range that probably encompasses several
hectares, and is usually based on a single area of contiguous
forest, with satellite colonies in adjacent smaller woodlands.
Both sexes can be found at least a
kilometre away from the egg-laying localities,
assembling at so-called
master trees, of which there may be several
in a large woodland complex. The master trees are usually
mature oaks, but beeches,
poplars and conifers are also used. In
all cases the trees are tall specimens,
on high ground, typically on the brow of a hill.
At these trees the males indulge in spectacular "sorties", competing for the best vantage points.
Strings of 4 or 5 males can often be seen chasing in circles
around the tree tops.
are seen less often. They visit the master trees to find mates,
disperse to the egg-laying
sites, which are often on north facing
woodland edges, or in semi-shaded and low-lying areas of the
wood where there are high densities of sallow.
Apatura iris, male ©
domed eggs are laid singly on the upperside of sallow leaves.
used more frequently than the narrow-leaved
July 2005 I watched a female which in the course of 3 or 4 minutes
laid about 10 eggs at various heights between 2 and 5 metres on
broad-leaved and narrow-leaved sallows growing on both sides of a
track in a Wiltshire wood.
The eggs were laid on
of the trees. At other sites in Hampshire and Surrey I have
watched females ovipositing on low, sunlit leaves on woodland edge
sallows; and at a thicket in north-east Hampshire I have seen a
female oviposit at
eye-level on a totally shaded broad-leaved sallow.
When first laid
the eggs are pale green, but after about 5 days they develop a
dark purplish band near the base. They hatch after about 14 days
and the newly hatched larva makes it's first meal of the eggshell.
young larva is greyish-brown and has 2 prominent horns on its head. It
feeds until October and then enters
hibernation while in the 2nd or 3rd instar. It
spends the winter resting on a silk pad spun
on the upperside of a withered sallow leaf, or in the fork of a twig on the damper and shadier
north or east facing side of the
tree. It resumes
feeding in early April.
When fully grown in
mid-June the larva is plump and
green. It is marked along the sides with dark-edged
diagonal cream stripes that perfectly simulate the veins
of a leaf. Two horns project forward from
the head, and the
body is strongly tapered at the tail. It is quite
unlike that of any other British butterfly or moth.
larva rests by daytime along the midrib on the upper
surface of a leaf. It periodically nibbles at the tissue either side, leaving
the midrib and leaf tip intact. At dusk it vacates it's resting
place and wanders all over the tree to feed. It lays a near-invisible trail of fine silk along it's route, and uses this as a
map to return to it's "home" leaf before dawn.
The chrysalis, which
wriggles frantically like a wet fish if touched, is a beautiful shade of
translucent silvery green, marked on the abdomen with short
whitish diagonal dashes. It is slightly flattened in shape. The
camouflage is so perfect that it is virtually impossible to locate, as it hangs suspended by the cremaster from a sallow leaf.
The pupal stage lasts for about 14 days.
begin emerging in late June and early July,
although they tend to emerge a week or two later if the early
summer has been cool. They remain on the wing until early August.
spend most of their time resting high in
trees, the males
favouring oaks while the females more often rest in tall sallows.
particular may spend an hour or more on their tree-top perches,
especially if the weather is cloudy or breezy. When the sun
appears, even if only for a brief period, the males take flight
and circle around the vicinity in search of food sources.
Both sexes will
feed at aphid secretions which often coat the upper
surface of sallow or oak leaves. They are also strongly attracted
runs. Males additionally feed at carrion, but are most often encountered when
imbibing fluids from carnivore dung or urine-soaked ground. These
provide them with essential alkaloids which are passed to females during copulation.
are sometimes seen
moisture from forest tracks between bouts of egg-laying, but do
not visit carrion or dung.
Apatura iris, male ©
July 1984 I
no less than
6 males feeding at
the carcass of a roe deer that was floating in an open cesspit in
The butterflies were so
stupefied by their
unsavoury meal that 2 of them remained on the carcass as I lassoed
a rope around the antlers and hauled it to the edge of the cesspit
to take photographs !
at about 8.30am
or later if
cooler or slightly
and can continue
until 12.30pm or later although there is usually a lull in
activity between noon and 2pm.
Sometimes a male will spend an hour or more on the ground without
Further puddling sometimes occurs
in the late afternoon
at about 6.00 -
7.00pm if it remains sunny.
In the early afternoon both sexes fly to the highest point in the
forest - the "master tree", typically a tall oak. As many as 6 or
7 may gather there on any particular day. Males usually arrive
first, and soon begin to chase each other around in circles,
competing to obtain the best "throne" - usually a
prominent clump of leaves on which they sit to await the arrival
of the females.
When a female appears the dominant male charges after her,
followed by any other males at the tree, and the butterflies fly
in a string, one behind the other, following the female as she
flits and glides around the upper branches.
The strongest and most aggressive male eventually chases off his
lesser rivals, and then follows the female until she settles on a
sunlit clump of leaves, often half a kilometre or more distant
from the master tree. Copulation takes place
pair spend most of the remaining afternoon sitting on their love
nest, but sometimes fly in tandem from one branch to another, or
more rarely descend to ground level. In
July 1986 for example,
watching a mud-puddling male in a Surrey wood, I saw a copulated
down from an oak, and settle on gravel. When I approached,
they flew up into another tall oak, settling near the top of the tree.
On another occasion
pair late in the afternoon, at a height of about 6 metres in a
spruce. The pair were still copulating at 7.00pm, when I had to
leave, and I suspect that they remained joined until dusk, or
possibly until the following morning.
In some years prolonged periods of
dull or rainy
weather occur during the flight season. Then when the sun does
briefly appear, a frenzy of courtship, mating and egg-laying
They are able to make the most of very limited
opportunities, e.g. weather conditions during throughout the 2007 flight
season in the UK were cool, overcast and often wet, with precious
little time for mate location or egg laying. Nevertheless 2008 and
2009 produced the highest Purple Emperor counts
on record. Similarly in 2012 Britain experienced atrocious
weather, with cool wet and windy conditions lasting from early May
until late July. The weather then suddenly changed and became very
hot and sunny for about a week, during which time the butterflies
emerged en masse, and were able to lay a large number of eggs.