Nature · Insects & other invertebrates

Peacock butterfly

On the wing July–September and again March–May · wingspan 63–69 mm

Aglais io — Nymphalidae (brush-footed butterflies)

The most instantly recognisable British butterfly: a deep maroon-red insect carrying a huge false eye on each of its four wings. Common across the whole of Britain and Ireland, it breeds on common nettle and hibernates as an adult, so it is among the first butterflies of spring and one of the last of autumn. Its defence is pure theatre — it sits with wings shut looking like a dead leaf, then snaps them open to flash four staring eyes at whatever came too close.

How to spot them

▸Four large blue-and-yellow eyespots, one on each wing, on a rich maroon-red ground
▸Underside almost black and finely striated — with wings closed it is a dead leaf
▸Hisses or rasps audibly when disturbed, by rubbing the wing veins together
▸Two flight periods with a gap: fresh adults in late summer, worn adults again on the first warm days of spring
▸Caterpillars velvet-black with white speckles and branched spines, in a communal silk web on nettles

How to know it

Four large blue-and-yellow eyespots, one on each of its four wings, on a maroon-red ground

Peacock butterfly — hence the name; the eyespots startle small birds.

Snaps its wings open to flash false eyes and hisses by rasping its wing veins together

Peacock butterfly, whose two-part defence is startle plus sound.

Sits on a woodpile with wings closed and is indistinguishable from a dead leaf, the underside being almost black

Peacock butterfly — the plainest underside of any common British butterfly.

Hibernates as an adult in a shed, hollow tree or roof space and emerges into the first warm March sun

Peacock butterfly, one of only a handful of British butterflies to overwinter as an adult.

Spiny black white-speckled caterpillars feeding in a communal web on a bed of common nettle

Peacock butterfly; the small tortoiseshell's larvae share the habit but are greener and yellow-striped.

Formerly placed in the genus Inachis, and named for a princess of Greek myth turned into a heifer

Peacock butterfly — Aglais io, once Inachis io, after Io.

Quick-fire facts

•Scientific name Aglais io; it was long known as Inachis io and earlier as Nymphalis io
•The only British butterfly with four large eyespots — one on each wing
•Widespread and increasing: it has spread north through Scotland in recent decades
•Larval foodplant is common nettle (Urtica dioica), occasionally hop
•Adults crowd onto buddleia in late summer and onto ivy blossom and rotting fruit in autumn
•A single generation must last from July through the winter to the following spring, making it one of the longest-lived British butterflies as an adult
•Butterfly Conservation lists it as a species of least conservation concern in the UK
•Both the peacock and the small tortoiseshell hibernate as adults; the painted lady cannot, and dies out each British winter

Drill it — 7 cards

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Sources

Butterfly Conservation — Peacock
Paul D. Brock — Britain's Insects: A Field Guide to the Insects of Great Britain and Ireland