The purple emperor is our largest (female wing span is 70-92mm) and most impressive butterfly. It inhabits three annually used territories on the commons.
Where to look
The most well-known and visited is Hill Farm, where High Point Path suddenly begins to climb uphill. There are two other annually used territories close to the Mark Oak car park. Here the tallest Turkey Oak has been used for many years.
Foodplant - goat willow and grey willow
Areas on the commons are managed to promote the young growth of willow in accessible areas, such as newly created ‘scallops’ along carefully widened woodland rides. Recent studies suggest that large groups of willow are especially attractive targets for egg-laying female purple emperors on the common.
The white admiral has a graceful flight and soars and glides close to the contours of oak trees. It’s smaller than the purple emperor and has more rounded wings.
Where to look
The sunny rides and tracks, avoiding the more open areas. High Point Path is a particularly good location.
Foodplant - honeysuckle in partial shade
White admiral females look for shady honeysuckle leaves to lay their small, shiny grey/brown, sea-urchin-like (including the spines) eggs. If too many shade providers, oaks and scrub hazels, are removed from the woodland edge the interior sunny honeysuckle leaves will be abandoned by the white admirals.
The silver-washed fritillary is a large orange-brown butterfly chequered with black spots. The male is brighter in colour but the female is slightly larger.
Where to look
High Point Path, together with the white admirals along the sunny, widened rides and tracks. Females can be seen busily depositing their eggs in the more shady areas.
Foodplant - violet, shady woodland floor
Silver-washed fritillary females, after finding violet leaves on the woodland floor, deposit their eggs on nearby tree trunks, most often oak at Bookham. The violets have to be growing in dappled shade and not overgrown by brambles and grasses. After hatching, within a fortnight, the tiny larvae immediately hibernate in the crevices of the oak bark, not emerging to feed upon violet leaves until the following spring.
You can also find common blue and small butterflies on the Plains. This area is managed in the summer by cattle grazing, which frees their caterpillar foodplants (bird's-foot trefoil and sorrel) from choking grasses.
Other grassland species, the small skipper and Essex skipper, thrive where trees have recently been cleared and prolific grass has been allowed to grow. Reduced numbers can also been seen on the Plains.
Ken Willmott FRES, Volunteer and Butterfly Conservation Surrey/SW London branch Conservation Adviser