''Apatura iris'', the purple emperor, is a
Palearctic
The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa.
The realm consists of several bioregions: the Euro-Sibe ...
butterfly
Butterflies are insects in the macrolepidopteran clade Rhopalocera from the Order (biology), order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The ...
of the family
Nymphalidae.
Description
Adults have dark brown wings with white bands and spots, and a small orange ring on each of the hindwings. Males have a wingspan of , and have a purple-blue sheen caused by
iridescence
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...
that the slightly larger (80–92 mm) females lack.
[Heath J. & Maitland Emmet A. (1989) ''The Moths and Butterflies of Great Britain and Ireland'', Vol.7 Part 1, Harley Books Ltd., Colchester: ] The
larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
(caterpillars) are green with white and yellow markings, and have two large "horns" at the anterior end and a smaller one at the posterior.
Apatura iris MHNT CUT 2013 3 18 Compiegne Dos.jpg, Dorsal side
Apatura iris MHNT CUT 2013 3 18 Compiegne Ventre.jpg, Ventral side
Habits
Females spend most of their lives in the tree canopy, favouring dense and mature
oak
An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
woodlands, coming down only to lay their eggs on the small willow bushes that grow in clearings and
bridleways
A bridle path, also bridleway, equestrian trail, horse riding path, ride, bridle road, or horse trail, is a trail or a thoroughfare that is used by people riding on horses. Trails originally created for use by horses often now serve a wider r ...
.
[Kirby W.F. (1903) ''The Butterflies and Moths of Europe'', Cassell & Co. Ltd., London: 432 pp.][South R. (1921) ''The Butterflies of the British Isles'', (Second edition), Frederick Warne & Co. Ltd., London: 210 pp.] Males also spend much of their time in the tree tops, defending their territory from rivals, though they will sometimes descend to drink from puddles or feed. Unlike most butterflies, the purple emperor does not feed from flowers but instead on the
honeydew secreted by
aphids, sap oozing from oak trees, and on dung, urine, and animal carcasses.
[
]Richard South
Richard South FRES (July 1846 – 28 March 1932) was an English entomologist who specialised in Lepidoptera (butterflies and moths), particularly the smaller moths. Life and work
South was born at Cochran Terrace in Marylebone, London, England ...
noted that collectors once used animal carcasses "in a somewhat advanced state of decay" to lure the males down to the ground, adding that this practice was "unsportsmanlike"; otherwise one needed a "high net" mounted on a pole about 14 or 15 feet (about 4.5 metres) in length to capture them.[ Heslop ''et al''. noted that the males' penchant for ]roadkill
Roadkill is an animal or animals that have been struck and killed by drivers of motor vehicles on highways. Wildlife-vehicle collisions (WVC) have increasingly been the topic of academic research to understand the causes, and how it can be mi ...
can often cause them to be killed by cars.[
]
Life cycle
They lay eggs in late summer on the upperside of sallow leaves, preferring the broad-leaved sallow, '' Salix caprea'', but they will also use the narrow-leaved sallow, ''Salix atrocinerea
''Salix atrocinerea'', commonly called grey willow or large gray willow, is a species of willow. It is a bush or small tree up to tall. As a pioneer species of willow, it quickly colonizes poor soils.
Distribution
The grey willow distribution ...
'', and various species of poplar.[Heslop I.R.P., Hyde G.E. & Stockley R.E. (1964) ''Notes and Views of the Purple Emperor'', Southern Publishing Co. Ltd., Brighton: 248 pp.] (Poplar is a more common food plant in continental Europe than in the British Isles.[) After hatching, the ]larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
will lie along the midrib
This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...
of the leaf where they are well camouflaged, and feed only at night. During the winter they hibernate in the forks of sallow branches, where they change colour from green to brown to match their surroundings. (The larvae are variously stated to be reach 35–40 mm long when fully fed[ or 55–56 mm;][ it is hard to give definitive measurements, given that they lack a rigid structure.) The following June they form a pale green ]chrysalis
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
, 30–35 mm long and 12–15 mm in width,[ resembling a leaf shoot. The adults usually emerge in July, flying well into August.
]
Distribution
''Apatura iris'' is widely distributed in dense, broadleaved woodlands throughout Europe including southern Britain, and across the Palearctic
The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa.
The realm consists of several bioregions: the Euro-Sibe ...
to central and western China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
.[ Different ]subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
are found across the region (see below).
British Isles
In Victorian times this species was regarded as being common in southern England, as far north as the river Humber,[ but since then it has experienced a sharp decline in both range and numbers. This decline started in the first part of the twentieth century (it was noted by South, for example, writing in 1921)][ and by the 1960s it was relatively scarce, being confined to old broadleaved woodlands in a few counties in south-east England.][ Heslop ''et al''. ascribed the decline to ]habitat fragmentation
Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes ...
and loss, starting before the First World War but accelerated by the increased demand for timber during that war, causing old woodlands to be clear felled to make way for commercial forestry crops, especially softwoods. This rendered large parts of its former habitat unsuitable, and it died out in those areas. This process continued after the Second World War for the same reason. Heslop estimated from his personal observation that "the minimum number of individual imagines (adults) required to sustain a viable colony in an average year is one thousand";[ independent confirmation of this has not been found.
South believed that once they had become uncommon, increased collecting had contributed "to the monarch's destruction" in many areas.][ By 1989 the species had a stronghold in the remaining large broadleaved woodlands of Hampshire, ]Surrey
Surrey () is a ceremonial and non-metropolitan county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant urban areas which form part of the Greater London Built-up Area. ...
and Sussex
Sussex (), from the Old English (), is a historic county in South East England that was formerly an independent medieval Anglo-Saxon kingdom. It is bounded to the west by Hampshire, north by Surrey, northeast by Kent, south by the English ...
, but was still found in scattered localities elsewhere across southern England.[ It has returned in large numbers to the Knepp estate in Sussex following re-wilding, as described by ]Isabella Tree
Isabella Tree, Lady Burrell (born 1964) is a British author and travel journalist. She is author of the Richard Jefferies Society Literature Award-winning book ''Wilding: the return of nature to a British farm'' that describes the creation of Kn ...
.
South noted that it had not been recorded from Scotland, and only doubtfully from Ireland, adding that "in Wales it is only found in Monmouthshire
Monmouthshire ( cy, Sir Fynwy) is a county in the south-east of Wales. The name derives from the historic county of the same name; the modern county covers the eastern three-fifths of the historic county. The largest town is Abergavenny, with ...
."[
]
Subspecies
*''Apatura iris iris''
*''Apatura iris bieti'' Oberthür, 1885 (Tibet, western and central China)
*''Apatura iris xanthina'' Oberthür, 1909
*''Apatura iris kansuensis'' O. Bang-Haas, 1933
*''Apatura iris amurensis'' Stichel, 909/small> (Amur, Ussuri)
Cultural reference
A specimen of ''Apatura iris'' plays a key role in solving a murder mystery in Robert W. Chambers' 1897 short story, "The Purple Emperor." The species is also mentioned in Tolkien’s '' The Hobbit'', in chapter 8, “Flies and Spiders”.
References
External links
Purple emperor at Butterfly Conservation
Purple emperor at UK Butterflies
{{taxonbar, from=Q30982
Apaturinae
Butterflies of Europe
Butterflies described in 1758
Taxa named by Carl Linnaeus