Purple Emperor

Apatura iris (a-pa-TOO-ruh EYE-riss)

Purple Emperor, Botany Bay, 28 June 2009
Photo © Neil Hulme
 

Wingspan
70 - 92mm

Checklist Number
59.022

Family:Nymphalidae (Swainson, 1827)
Subfamily:Apaturinae (Boisduval, 1840)
Tribe:Apaturini (Boisduval, 1840)
Genus:Apatura (Fabricius, 1807)
Subgenus: 
Species:iris (Linnaeus, 1758)

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Introduction

The Purple Emperor is a magnificent and elusive insect that is actively sought out by the many subjects of "His Majesty", as the male butterfly is affectionately known. This butterfly spends most of its time in the woodland canopy where it feeds on aphid honeydew, with the occasional close encounter when it comes down to feed on sap runs or, in the case of the male, animal droppings, carrion or moist ground that provide much-needed salts and minerals. Those that make pilgrimages to see this spectacular creature will often try and lure the males down from the canopy using all manner of temptations - including banana skins and shrimp paste.

The male butterfly is one of the most beautiful of all of the butterflies found in the British Isles. From certain angles it appears to have black wings intersected with white bands. However, when the wings are at a certain angle to the sun, the most beautiful purple sheen is displayed, a result of light being refracted from the structures of the wing scales. The female, on the other hand, is a deep brown and does not possess the purple sheen found in the male.

This is one of the most-widely studied and written about butterflies in the British Isles. The classic work "Notes and Views of the Purple Emperor" by Heslop, Hyde and Stockley is dedicated to this butterfly, as is the modern-day equivalent - the excellent website The Purple Empire. This butterfly is confined to deciduous woodland in central southern England, between South Wiltshire and South Hampshire in the west, Surrey and West Sussex in the east, and Oxfordshire and Hertfordshire in the north, with scattered colonies elsewhere. It is not found in the north of England, Scotland, Ireland, the Isle of Man or the Channel Islands and has not been seen in Wales since the 1930s. Colonies vary in size, some being very small with just a dozen or so adults forming a viable colony.

Apatura iris

This species was first defined in Linnaeus (1758) as shown here (type locality: Germany, England etc.).

Purple Emperor - Fermyn Wood 2-July-2014

Male
Photo © Neil Hulme

Purple Emperor - Fermyn Woods - 14.07.13

Male Underside
Photo © Rosalyn

Purple Emperor (female), Chiddingfold Forest (17 July 2013)

Female
Photo © Mark Colvin

Purple Emperor (female) Bernwood Forest Oxfordshire 4th July 2011

Female Underside
Photo © millerd

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Conservation Status

Determining the status of this species has always been problematic given its elusive nature and, although its status is considered relatively-stable, is still considered a species of conservation concern.

UK BAP StatusDistribution Trend (%)Population Trend (%)
Species of Conservation Concern
Increase+44
Increase+31

The table above shows the distribution and population trends of species regularly found in the British Isles. The distribution trend represents a comparison between data for the periods 1995-1999 and 2005-2009. The information provided is taken from the Butterfly Conservation report The State of the UK's Butterflies 2011. The UK BAP status is taken from the UK Biodiversity Action Plan (UK BAP) (2007 review).

Habitat

This is a butterfly of large expanses of deciduous woodland, usually those containing oaks, but less-frequently beech and other species.

Distribution

 

Click here to see the distribution of this species or here to see the distribution of this species together with specific site information overlaid. Alternatively, select one of the sites listed below.

Sites
Alice Holt Forest, Ashtead Common, Bagmoor Common, Bentley Station Meadow, Bentley Wood, Bernwood Forest, Binsted Wood, Blackmoor Copse, Bookham Common, Botley Wood, Box Hill Woods, Bricket Wood Common, Broxbourne Wood NNR, Carpenters Down Wood, Ebernoe Common and Butcherland, Farley Mount Country Park, Fermyn Wood, Finemere Wood, Grovely Wood, Havant Thicket, Heyshott Escarpment, Lady Wood, Marks Hall Estate, Norbury Park, Norton Green, Oaken Wood, Oakley Wood, Old Down, Basingstoke, Pamber Forest, Piddington Wood, Ranmore Woods, Rushbeds Wood, Southwater Woods, Springhead, Thundery Meadow, Tring Park, Vann lake, Wallis Wood, Warburg Reserve, Warnham LNR, Whitecross Green Wood, Whiteley Pastures, Wicken Wood, Woodwalton Fen

Life Cycle

There is a single generation each year. The adult butterfly emerges in early July, sometimes at the end of June in good years, with a peak in the second and third weeks of July.

The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.

Imago

This species is best seen in early morning and again in late afternoon, when the males will come down to the ground to feed on moisture from damp earth and animal droppings. The males are sometimes so engrossed in feeding that they will spend over an hour feeding in the same place, each displaying its characteristic yellow proboscis. The males are also notorious for feeding on mud and other debris that has gathered on surfaces of cars parked within the woodland. They are also partial to sweat and readily land on observers. However, both male and female spend the majority of their time resting high in the tree canopy and out of sight.

In late morning, the males will fly off and ultimately congregate at so-called "master trees" that provide a vantage point for intercepting passing females. These trees are typically at a high point in the wood, such as trees growing on the summit of a hill, and the same trees are used year after year. Locating a master tree is one of the best ways to catch a glimpse of this elusive insect. Seeing the males battle it out for the best vantage points, with flashes of purple as the light hits their wings, is an amazing spectacle.

When a virgin female is encountered, the pair fly off and settle in the canopy where mating takes place. If the female has already mated, then she has the curious habit of descending straight to the ground, where the male ultimately loses interest and returns to his perch.

Adults feed primarily on Honeydew / Sap. Carrion and Dung are also used.

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Ovum

When egg-laying, the female "strikes" the sallow, as it is known, where she enters the tree and disappears within to lay a single egg on the upperside of a sallow leaf that is in half-shade. Eggs are usually laid on leaves toward the crown of the tree at various heights. Eggs are blue-green when first laid but, after a few days, the base of the egg turns purple giving the egg a distinct 2-tone appearance. Eggs hatch in 9 or 10 days, depending on the weather.

Purple Emperor ovum - Rockingham Forest 08.07.14.

Photo © Tony Moore
09-Jul-2014

Purple Emperor - ovum - Savernake Forest, Wiltshire - 26-Jul-14-2

Photo © Pete Eeles
26-Jul-2014

Purple Emperor - ovum - Wiltshire Wood - 23-Aug-13

Photo © Pete Eeles
23-Aug-2013

Purple Emperor egg, August 2010, Switzerland

Photo © Padfield
Switzerland

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Larva

On hatching, the green larva eats its eggshell before moving to the tip of the Sallow leaf, where it rests facing the leaf stalk. It feeds by day on each side of its resting place, leaving characteristic feeding damage. After the first moult, the larva is a curious beast, being adorned with 2 horns that grow out of the head. After the second moult the larva turns light brown and moves to the fork of a twig or next to a Sallow bud, where it overwinters on a silk pad with its body flush against the surface on which it is lying.

Larvae emerge from hibernation around the middle of April just as the Sallow buds are starting to expand. The larva initially feeds on the unfurling buds, until the leaves are fully-developed. The larva will then rest on a particular Sallow leaf, which is always left intact, and from which it travels to feed, returning after it has completed its meal. When at rest, the larva also sits with the front of its body slightly raised off its leaf thereby minimising any shadow that might give its presence away. It is also beautifully camouflaged with several subtle yellow stripes along the length of its body that perfectly match those of pale veins of the Sallow leaf on which it sits.

When ready to pupate, the larva travels to find a suitable pupation site, and turns a much paler green. The larva will move to the underside of the chosen Sallow leaf and spend 1 or 2 days building a pad of silk from which the pupa will be suspended. At first, the larva rests with its head facing the leaf stalk. As the time for pupation nears, the larva reverses this position, with its head facing the leaf tip. The larva has 4 moults in total.

The primary larval foodplant is Goat Willow (Salix caprea). Crack-willow (Salix fragilis) and Grey Willow (Salix cinerea) are also used.

Purple Emperor - larva - Thatcham - 20-Apr-11 (2) {REARED}

Photo © Pete Eeles

Purple Emperor larva 2, pre-hibernation, Wilts Wood, 11 October 2009

Photo © Neil Hulme
11-Oct-2009

Purple Emperor - larva 3rd instar - Wiltshire Wood - 10-Mar-14-7

Photo © Pete Eeles
10-Mar-2014

Purple Emperor - larva - Wiltshire Wood - 24-Aug-13-5

Photo © Pete Eeles
24-Aug-2013

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Pupa

The pupa is arguably the most difficult stage to find in the wild since, like the larva, it is perfectly disguised, matching the shades of green of the sallow leaf from which it is suspended upside-down, attached to the leaf by the cremaster. The pupa is a curious shape, being rather flattened so that, from the side, it looks plump whereas, from the back, it appears rather slim. This stage lasts around 2 weeks.

Purple Emperor - pupa - Thatcham - 19-Jun-05 (7) [REARED]

Photo © Pete Eeles
19-Jun-2005

Purple Emperor - pupa - Thatcham - 27-May-11 (1) {REARED}

Photo © Pete Eeles

Purple Emperor - pupa - Thatcham - 13-Jun-14 [REARED]-2

Photo © Pete Eeles
13-Jun-2014

Purple Emperor - pupa - Thatcham - 01-Jun-11 (1) {REARED}

Photo © Pete Eeles

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Aberrations

Description to be completed.

This section shows those aberrations for which there is a corresponding image. Click here to see the descriptions of other aberrations for this species.

ab. afflicta (Cabeau.Rev.Mens.Soc.Ent.Nam.1910.p.33.,fig.Lamb.30.pl.3.f.1.)

Forewings with only three little white spots in the form of a triangle, the apical, subapical and second marginal. Hindwings without a clear marginal band or one scarcely indicated, the transverse band reduced to two or three little white spots, sometimes greyish, in the lower part of the wing, the upper spots being list in the ground colour. Also belonging to this form, specimens with the forewings spots, apart from those mentioned above, showing in greyish but the hindwings band is always reduced as above. The figure in Lamb.30.pl.3.f.1 shows the forewings with seven whitish spots so presumably the form is mainly characterised by the absence of a complete white band on the hindwings.

Apatura iris (ab. afflicta) - Fermyn 29th June 2011

Photo © NickB

Purple Emperor (ab. afflicta) - Fermyn Wood - 29th June 2011

Photo © PhiliB
29-Jun-2011

Purple Emperor (ab. afflicta) - Fermyn Wood 29-June-2011

Photo © Neil Hulme
29-Jun-2011

Purple Emperor (ab. afflicta) - Fermyn Wood 29-June-2011

Photo © Neil Hulme
29-Jun-2011

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ab. lugenda (Cabeau.Rev.Mens.Soc.Ent.Nam.1910.p.34.)

Forewings with three small white spots as in ab. afflicta Cabeau. These are in the form of a triangle, one apical, the second subapical and the third marginal. Hindwings with the white transverse band completely absent, one sees only some bluish hairs. There is no light antemarginal band and the eye at the anal angle is pupilled with bluish-grey.

Purple Emperor - ab. lugenda - Straits Inclosure - Alice Holt Forest, Hampshire - 28.6.09 [Matthew Oates]

Photo © Matthew Oates
28-Jun-2009

Purple Emperor - ab. lugenda - Straits Inclosure - Alice Holt Forest, Hampshire - 28.6.09(3) [Matthew Oates]

Photo © Matthew Oates
28-Jun-2009

Purple Emperor ab. Fermyn Wood, 11am 26-July-2012

Photo © Charles Nicol

Purple Emperor - ab. lugenda - Straits Inclosure - Alice Holt Forest, Hampshire - 28.6.09(6) [Matthew Oates]

Photo © Matthew Oates
28-Jun-2009

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ab. stictica (Cabeau.Rev.Mens.Soc.Ent.Nam.1910.p.32.)

Forewings somewhat paler than the type [typical form] with eight or nine white spots, very small and clearly separated. The white band of the hindwings is very narrow, composed of four or five white spots separated by the black nervures, which are pronounced. The other spots are greyish and sunk into the ground colour.

Purple Emperor (ab. stictica) - Fermyn Wood 27-July-2012

Photo © Neil Hulme
27-Jul-2012

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Similar Species

No similar species found.

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The following links provide additional information on this butterfly.

References

The species description provided here references the following publications:

ReferenceDetails
Boisduval (1840) Boisduval, J.A. (1840) Genera et index methodicus Europaeorum lepidopterum.
Fabricius (1807) Fabricius, J.C. (1807) Magazin für Insektenkunde, herausgegeben von Karl Illiger.
Linnaeus (1758) Linnaeus, C. (1758) Systema Naturae. Edition 10.
Swainson (1827) Swainson, W. (1827) A Sketch of the Natural Affinities of the Lepidoptera Diurna of Latreille. The Philosophical magazine : or Annals of chemistry, mathematics, astronomy, natural history and general science.