Key facts
- Gaelic name: Dealan-dè nam boglaichean
- Wingspan: 42 – 48mm
- Distribution in UK: Restricted to western Britain and Ireland
- When to see: May – July
- Status: UK BAP status: Priority Species; Butterfly Conservation priority: High; European Status: Vulnerable
- Species on the Edge areas: Argyll and Inner Hebrides
Species information
How to identify
The marsh fritillary is a brightly coloured butterfly, with a mosaic of orange, yellow, and brown markings on the upper surface of both the forewings and hindwings, which form distinct rows of the same colour. There is a prominent row of small black spots towards the outer edge of each hindwing.
Lifecycle
Adults fly from late May until the end of June. Females lay their eggs in batches of 20 to 100 on the leaves of larger specimens of the sole foodplant of their caterpillars, Devil’s-bit Scabious. You can recognise this plant from its distinctive purple flower heads held on long stalks in late summer. The caterpillars live communally within a conspicuous and protective silk web which they spin themselves. They have spikes along their bodies and are brown at first but turn black in spring. You can recognise the webs in late summer or spring because they are denser than spider webs and look rather slimy on damp days, and you will often see the caterpillars on or inside the webs. You may also notice the brown remains of scabious leaves they have previously been feeding upon, dark spots of caterpillar droppings, and remains of the previous webs as they move from plant to plant.
The caterpillars hibernate over the winter inside a smaller web, deep within a grass tussock where they can even survive temporary flooding. The caterpillars emerge from hibernation in March and build new webs and bask communally in the spring sunshine, often on the outside of their web. They commence feeding before dispersing and pupating (making a chrysalis) on plants nearby, from which the adult butterflies emerge from late May.
The butterfly forms close-knit colonies on discrete patches of habitat (typically across 5-20 hectares). Marsh Fritillary populations can fluctuate tremendously in size from year to year, often declining due to a combination of factors including parasitic wasps whose larvae feed on and kill the butterfly larvae, unfavourable site conditions, and poor weather. Individual colonies can contract down to thinly-scattered sites in lean years but can recover quickly and spread out to new sites in good years.
Distribution
The Marsh Fritillary butterfly was once widespread in Britain and Ireland but has declined severely and is now extinct across much of Britain.
Scotland still holds some of the largest and best-connected populations in Europe. Here it is restricted to coastal areas of mainland Argyll
and the Inner Hebrides.
and the Inner Hebrides.
Marsh fritillary UK distribution map. Credit: Butterfly Conservation https://butterfly-conservation.org/butterflies/marsh-fritillary
Habitat and feeding
The butterfly requires damp flower-rich grassland or moorland where there is an abundance of Devil’s-bit Scabious, its sole larval foodplant.
Conservation status
- Priority Species in UK Biodiversity Action Plan UK Red List (Vulnerable)
- Fully protected under Section 9 of the Wildlife and Countryside Act (1981)
- EC Habitats and Species Directive (Annexe II)
- Scottish Biodiversity List species
Threats
The main threats to Marsh Fritillary include over- or under-grazing, and the isolation of existing colonies.
What Species on the Edge is doing
-
Monitoring and surveying of Marsh Fritillary populations and their habitat
- Habitat management
- Creating habitat management plans with landowners and managers
- Engaging with local communities to increase awareness and encourage local action for Marsh Fritillary
- Survey and monitoring training sessions for volunteers
- Landowner training in habitat management and species monitoring
How you can help
Survey and monitoring
We need your help to survey and monitor the distribution and annual fluctuations in the butterfly’s population in Scotland. This can be done through a single count of the caterpillar webs in late summer. If you would like to help, or have seen Marsh Fritillary, we would love to hear from you. Contact scotland@butterfly-conservation.org.
If you have seen a Marsh Fritillary adult or web, please send your sightings to us using the free iRecord Butterflies app or using the email address above.
Do you have Marsh Fritillary on your land?
If you have the right habitat on your land, we are happy to provide free advice on management and conduct surveys for the species and help with monitoring.
Managing land for the Marsh Fritillary
The long-term survival of the Marsh Fritillary is more likely if the sites are linked, enabling an exchange of adults between neighbouring colonies in a landscape. The loss of suitable habitat can make the surviving populations more fragmented and thus more isolated and vulnerable to extinction.
The overall aim of management is to encourage a patchwork of short and tall vegetation 5-25cm long, with areas of abundant Devil’s-bit Scabious, with a good supply of nectar sources in sunny, sheltered situations.
Grazing
A degree of light grazing, preferably by cattle or ponies, is essential to maintain flower-rich areas and Devil’s-bit Scabious in an open sward. At most sites, extensive year-round grazing is the ideal (0.2-0.3 LU/ha/year). However, seasonal grazing at a similar stocking density over the autumn and winter can also keep sites in suitable condition. Sheep grazing needs to be managed carefully as the habitat can become dominated by rushes rather than creating the varied vegetation heights achieved by cattle. Stocking levels need to be very low or absent during the late summer (<0.1LU/ha) as sheep selectively feed on Devil’s-bit Scabious flowers and can thus reduce and even eliminate it from sites over time.
Mowing
Blanket mowing is generally unsuitable as it removes the patchwork of short and tall vegetation. However, it may be used as a restoration tool where tussocky grasses such as Purple Moor-grass or rushes have become dominant. The area should be cut in sections over several seasons but avoiding patches of suitable habitat.
Scrub cutting
Where scrub is encroaching into Marsh Fritillary habitat, removal by cutting is best done between October and the end of March. Uncontrolled burning, drainage, agricultural improvement and cessation of grazing can all be detrimental.
Gallery
