Fabriciana adippe, the high brown fritillary, is a large and brightly colored butterfly of the family Nymphalidae, native to Europe and across the Palearctic to Japan. It is known for being Great Britain's most threatened butterfly and is listed as a vulnerable species under the Wildlife and Countryside Act 1981. Like other fritillaries it is dependent on warm climates with violet-rich flora.
The high brown fritillary's wingspan is on average around 65 mm. Its upper wings are orange with black markings and the undersides are colored a duller orange with white and brown markings. While flying, it is very hard to distinguish from the dark green fritillary which has many of the same markings. The male and female fritillary share many of the same physical features.
Larvae are brown with a single longitudinal white stripe down the length of their body. Their bodies are covered in brown spikes which aid in camouflaging them from predators as they move among dead fern fronds.
This butterfly has many subspecies that span across Europe and throughout Asia and Africa, given that there are temperate temperatures in those regions. Northern Europe has seen a severe decline in fritillary population but it is still relatively abundant in other parts of Europe.
As of 2015, the high brown fritillary was the most threatened British butterfly species. Populations remain in four areas in Great Britain. The Morecambe Bay Limestone hills, the Glamorgan Brackenlands, Dartmoor and Exmoor all support a fritillary population, while it has declined in most other Northern European regions.
There are two main habitats that support high brown fritillary populations: bracken and limestone outcrops. Bracken habitats are found across its geographic range but limestone outcrops are specific to Great Britain.
These habitats are specific to Great Britain, especially to the limestone soils of the Morecambe Bay. These outcrops are usually created by human intervention and land management. Breeding persists on limestone soil or near bracken. Throughout the rest of Great Britain, populations are restricted to thick Bracken clumps.
Fritillaries in woodland habitats have been most severally affected by habitat loss. These butterflies relied heavily on coppicing, a land managing technique that has all but disappeared from Great Britain's countryside. The reduction of coppicing combined with replanting and new forest growth has several limited the places the fritillary can thrive, as bracken habitats are becoming rarer. Within bracken habitats, population loss is driven when bracken growth is too extreme or grazing animals trample the flora associated with the butterfly.
The high brown fritillary population, especially in Great Britain, is extremely threatened. It is extinct in over 90% of its former geographic range, making it a high priority for conservation efforts. The species was once widespread in the United Kingdom but has now greatly declined. It has legal protection in the UK under the 1981 Wildlife and Countryside Act. The British decline of the fritillary can be attributed to novel changes in land management, increasing during the 20th century.
