Aglais io (ag-LAR-iss EYE-oh)

Peacock, Findon Valley, Sussex 8-Aug-2012
Photo © Neil Hulme

Male: 63 - 68mm
Female: 67 - 75mm

Checklist Number

Family:NymphalidaeRafinesque, 1815
Subfamily:NymphalinaeRafinesque, 1815
Tribe:NymphaliniRafinesque, 1815
Genus:AglaisDalman, 1816
Species:io(Linnaeus, 1758)

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The Peacock is a familiar sight in gardens across the British Isles and is unmistakable, with quite spectacular eyes on the upperside of the hindwings that give this butterfly its name. These eyes must appear very threatening to predators, such as mice, that confront this butterfly head-on, where the body forming a "beak", as shown in the image below.

The underside is a different matter altogether, being almost black, providing perfect camouflage when the butterfly is at rest on a tree trunk, or when hibernating. In addition to camouflage and large eyes, the butterfly is able to make a hissing sound by rubbing its wings together that is audible to human ears. All in all, this butterfly must appear very threatening to any predator that might come across it. This is a highly mobile butterfly that occurs throughout the British Isles, including Orkney and Shetland, although it is not found in parts of northern Scotland. However, its range does seem to be increasing, with sightings from new areas being recorded every year.

Aglais io

This species was first defined in Linnaeus (1758) as shown here (type locality: Sweden).

Peacock - imago - Noar Hill - 30-Jul-04

Photo © Pete Eeles

Peacock, Longmoor, 20/07/2014

Male Underside
Photo © Pauline

Peacock Female - Chaldon, Surrey 9-April-11

Photo © Vince Massimo

Ovipositing Peacock - Coulsdon, Surrey 19-May-2013

Female Underside
Photo © Vince Massimo

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Conservation Status

Although small decreases in population have been observed, this species seems to be faring well and this common and widespread species has shown signs of colonising the few remaining areas in northern Scotland where it has not historically been found. This butterfly is not, therefore, a species of conservation concern.

UK BAP StatusDistribution Trend (%)Population Trend (%)
Not Listed

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).


This butterfly can turn up almost anywhere, given its broad distribution. This butterfly is often encountered while hibernating in outbuildings, such as a garage, shed or barn, where they are often in the company of other individuals. Other hibernation sites include hollow trees and wood piles, where their dark undersides provide excellent camouflage.



Click here to see the distribution of this species or here to see the distribution of this species together with specific site information overlaid.

Life Cycle

This butterfly is generally single-brooded. However, in good years, a small second brood may appear. Adults may be seen at any time of the year, with warm weather waking them from hibernation. The majority emerge from hibernation at the end of March and beginning of April. These mate and ultimately give rise to the next generation that emerges at the end 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.


The adults spend most of the morning nectaring. Males set up territories around midday, often on the sunny side of a wood, where they wait for a passing female. Males will fly up at any dark object, which is one way of sexing this species since the two sexes are very difficult to tell apart, being almost identical in appearance. When a female is found she flies off, trying to escape the male that is in pursuit. If he succeeds in staying with her then the pair mate. Females subsequently take great care when egg-laying, selecting foodplants that are in full sun.

Adults emerging in summer nectar on a variety of flowers, building up essential body fats before overwintering.

Adults feed primarily on Thistles (Cirsium spp. and Carduus spp.). Betony (Stachys officinalis), Bluebell (Hyacinthoides non-scriptus), Cuckooflower (Cardamine pratensis), Dandelion (Taraxacum agg.), Devil's-bit Scabious (Succisa pratensis), Fleabane (Pulicaria dysenterica), Hawkweeds (Hieracium/Hypochoeris), Hemp Agrimony (Eupatorium cannabinum), Honeydew / Sap, Marjoram (Origanum vulgare), Privet (Ligustrum vulgare), Ragwort (Senecio jacobaea), Teasel (Dipsacus fullonum), Water Mint (Mentha aquatica) and Yarrow (Achillea millefolium) are also used.

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Females lay one or more egg clusters of up to 400 eggs on the underside of a Nettle leaf. These are laid in untidy piles, rather than being laid neatly side-by-side. The nettle patches chosen are usually in a more-sheltered position than those selected by the Small Tortoiseshell. Eggs hatch in 1 to 3 weeks.

Peacock double egg mass (with parasitic wasp) - Coulsdon, Surrey 16-April-2014

Photo © Vince Massimo

Peacock double egg mass (with parasitic wasp) - Coulsdon, Surrey 16-April-2014

Photo © Vince Massimo

Peacock ova with mite - Hampshire 10-May-2015

Photo © jackz432r

Peacock ova - Coulsdon, Surrey 2-May-2013

Photo © Vince Massimo

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The behaviour of the larva is very similar to that of the Small Tortoiseshell, the two species often being seen together. In the first instar, Peacock larvae are very similar to those of the Small Tortoiseshell. However, mature Peacock larvae are jet black for the most part, whereas Small Tortoiseshell larvae are typically dark green with a pair of yellow stripes running down the length of their sides.

On emerging from their eggs, Peacock larvae build a communal web near the top of the plant and from which they emerge to bask and feed and are usually highly conspicuous. As the larvae grow, they move to new plants, building new webs along the way. Webs are decorated with shed larval skins and droppings and are easily found.

Larvae have several techniques to avoid predation. When disturbed, a group of larvae will often jerk their bodies from side to side in unison, which must be a formidable sight to any predator. The larvae will also regurgitate green fluid and will, if necessary, curl up in a ball and drop to the ground. Larvae feed both during the day and ay night. There are 4 moults in total.

The primary larval foodplant is Common Nettle (Urtica dioica). Hop (Humulus lupulus) and Small Nettle (Urtica urens) are also used.

Peacock larva pupating - Caterham, Surrey 16-July-2012

Photo © Vince Massimo

Peacock Larvae - Martin Down - 22-6-08

Photo © Gwenhwyfar

Peacock - Freshly Moulted Second Instar - Somerset - 01/06/14

Photo © William

Phobocampe confusa cocoons - Caterham, Surrey 8-July-2012

Photo © Vince Massimo

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The larvae disperse as they become fully grown, and eventually wander off to find a suitable pupation site. The pupa is formed head down, attached to a stem or leaf by the cremaster. The pupa has 2 colour forms - yellow and dark grey - the resulting colour depending on the site chosen for pupation. This stage lasts between 2 and 4 weeks, depending on temperature.

Peacock emerging, 26/07/2014, Liphook, reared

Photo © Pauline

Peacock pupa (3 hours 40 minutes before hatching) - Caterham, Surrey 30-July-2012

Photo © Vince Massimo

Peacock pupa (1 week old) - Caterham, Surrey 23-July-2012

Photo © Vince Massimo

Peacock - pupa - Thatcham - 15-Jul-09 (1) {REARED}

Photo © Pete Eeles

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Description to be completed.

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The following links provide additional information on this butterfly.


The species description provided here references the following publications:

Dalman (1816) Dalman, J.W. (1816) Kongl. Svenska Vetenskaps akademiens Handlingar.
Linnaeus (1758) Linnaeus, C. (1758) Systema Naturae. Edition 10.
Rafinesque (1815) Rafinesque, C.S. (1815) Analyse de la nature ou Tableau de l'univers et des corps organisés.