The High Brown Fritillary: England's Most Threatened Butterfly

1 July 2026

About the High Brown Fritillary

The High Brown Fritillary is a large, fast-flying butterfly with a bright orange upperwing patterned with black markings. The underwing shows distinctive silver spots with brown cell borders that separate it from the similar Silver-washed Fritillary. It is on the wing in June and July, flying in warm sunshine over bracken-covered slopes.

The species has declined catastrophically since the 1970s. It has been lost from over 95% of its former sites. The cause is habitat change: the loss of open, warm woodland and scrubby grassland where its larval foodplant, common dog-violet, grows in the right microclimate. Active conservation management is now essential to maintain the remaining populations.

Where to find them in the Lake District

The Morecambe Bay limestone hills — Arnside Knott and Warton Crag — are the main Lake District sites. The butterfly requires south-facing bracken slopes with abundant dog-violets in the litter beneath the bracken. Butterfly Conservation manages these sites with targeted scrub clearance and bracken management to maintain the open conditions the butterfly needs.

Arnside Knott (LA5 0AD) National Trust reserve is the more accessible site. The south-facing slopes above the woodland edge hold the main population. Visit on a warm, sunny day in late June or early July. Early afternoon, when the air temperature peaks, is when the butterflies are most active and visible.

Conservation

Butterfly Conservation runs targeted conservation work for the High Brown Fritillary at the Morecambe Bay sites. This involves scrub clearance to maintain open, warm habitat, bracken management to allow the dog-violet to establish, and annual population monitoring by transect survey.

The species is listed as a priority species under the UK Biodiversity Action Plan. If you visit Arnside Knott in July and see these butterflies, you are seeing a conservation success in action — a threatened species that still exists because people are managing specifically for it.