Purple Emperor

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What is a Purple Emperor?

The purple emperor is one of Britain’s most charismatic but elusive butterflies. This magnificent butterfly is the second largest butterfly in the UK and is as big as a small bird. The male has an iridescent purple sheen to its upper wings with white bands across the wings. The female is brown and larger than the male.

Purple emperors fly high in the treetops of large blocks of mature deciduous woodland and clusters of smaller woods from late June to early August. Goat willow, their caterpillar foodplant, is essential. Although usually associated with oak woodland, they also use ash, beech and Scots pine as ‘master trees’ for roosting, congregating and feeding on tree sap.

Why is the Purple Emperor important to the Surrey Hills?

The purple emperor is protected under the 1981 Wildlife and Countryside Act. It is restricted to southern and central England where numbers have declined by around 47% since the 1970s.  It is vulnerable to bad weather in the summer flight season. It is also threatened by lack of woodland management leading to a lack of willow for egg-laying; deer-browsing of young willow;  drainage of wet woodlands, and loss of woodland connectivity leading to the isolation of surviving populations.

Good management for this species will create/result in improved quality and extent of deciduous woodland and scrub habitat, particularly in damp areas suitable for goat willow.

What habitat does the Purple Emperor like?


Woodland is important because it is one of our most complex habitats and as such, can support more wildlife than almost any other UK habitat. Ancient woodland which has been continuously wooded since at least 1600 AD is particularly important, but younger secondary woodlands and even conifer plantations can be important for nature if managed sympathetically.

What can be done to benefit the Purple Emperor?

Improved habitat for the purple emperor also provides habitat opportunities for a range of other wildlife.  Goat willow foliage is eaten by the caterpillars of several moths, including the sallow kitten, sallow clearwing, dusky clearwing and lunar hornet clearwing.  The catkins or ’pussy willow’ provide an important early source of pollen and nectar for bees and other insects and birds such as the nightingale.

Opportunities to create/improve/extend suitable habitat for this species include:
  • Thinning to encourage the development of the woodland shrub layer
  • Promoting goat willow in the shrub layer
  • Controlling deer
  • Managing drainage to conserve damp woodland areas


Creating and managing areas for the Purple Emperor will help deliver the following benefits to communities:
  • Clean water
  • Clean air
  • Protection from and mitigation of environmental hazards
  • Mitigation of and adaptation to climate change
  • Thriving plants and wildlife
  • Beauty, heritage and engagement

These illustrations are by an artist taking part in a programme delivered by Watts Gallery Trust and funded by the Michael Varah Memorial Fund. This series of 30 Surrey Hills Indicator Species were commissioned by Surrey Hills Society and funded by Surrey Hills Trust Fund as part of the Making Space for Nature Exhibition.