Wiltshire and Swindon Biological Records Centre

Marsh Fritillary

27th February 2012

Marsh Fritillary larvae, Gilles San Martin

One of the more conspicuous fritillaries with adults displaying bright orange and yellow chequered wings when in flight between mid-May and mid-July, colonies could once be found throughout Britain in a variety of habitats from wet meadows to heaths and downlands. Due to changes in agricultural practices, today colonies are predominately limited to calcareous grassland. Easy to spot webs are produced in late summer by small black larvae who then overwinter, emerging in early spring to bask in the weak sunshine. Devil’s-bit scabious is the primary foodplant, although on calcareous grassland Field Scabious and Small Scabious may occasionally be used.

Latin name: Euphydryas aurinia

Population Numbers: With severe declines across Europe, Britain is considered to be a stronghold for the Marsh Fritillary. Despite this here in Britain 66% of colonies were lost between 1990 and 2000 leaving them restricted primarily to isolated parts of southwest England. In 2010 this species was recorded from 67 localities in Wiltshire (64 in 2009) but several of the known colonies are struggling to keep a foothold, particularly those that are fairly isolated. The Marsh Fritillary is protected under the EC Habitats and Species Directive and the Wildlife and Countryside Act (1981) and it is a priority UK Biodiversity Action Plan species.

Where to see and when: In early spring when the larvae re-emerge after winter, clusters of up to 150 can gather to bask in what sun there is. Keep your eyes peeled for this sight at Morgan’s Hill reserve, a small (13ha) reserve designated a Site of Special Scientific Interest (SSSI) for the orchid and butterfly species found there and the general high quality of the grassland. One particularly memorable year the entire reserve was dotted with larval nests, with the tiny clusters of black caterpillars looking almost like bits of dark wool. As they grew the caterpillars dispersed and a few months later in early June, the reserve was alight with the beautiful yellow and orange checker-board patterned wings as the adult butterflies emerged.

What’s being done: In the last 10 years nearly three quarters of British butterflies have been recorded as declining making sites like Morgan’s Hill increasingly important. The severe declines seen in the marsh fritillary are believed to be due to the deterioration of suitable habitats often caused by land drainage and changes in agricultural practices combined with the impacts of poor weather and inappropriate habitat management on small isolated sites.

View from the top of, and across, Morgans Hill

Devil’s-bit scabious, the marsh fritillary’s food plant, grows in a rosette at ground level and is therefore vulnerable to being overgrown by grasses and scrub or consumed by grazing livestock, effective management is consequently key. Managing for specialist butterfly species requires tailored management and it has been demonstrated that with sufficient effort, time and resources some populations can be maintained and even increased. The marsh fritillary has shown indications that it could be one of these tentative successes.

The deterioration of suitable habitats is believed to be the main cause behind the national butterfly decline and at Morgan’s Hill the grazing is managed to try and ensure conditions are suitable for the Marsh Fritillary in addition to several other species, which is a tricky balancing act on a small site, where species can have different habitat requirements. Thanks to Environmental Stewardship funding, the Trust has been working with a neighbouring farmer to increase the potential area of suitable habitat, by reintroducing grazing on an adjoining bank and assisting with the seeding of wildflower species on previously arable land. Results are looking promising, with Devil’s-bit scabious and other wildflower species recorded present last year.