Mountain Ringlet (Erebia epiphron) - PRIORITY SPECIES

Description

The Mountain Ringlet is a small dark brown butterfly with orange bands containing black spots on both upper and underwing surfaces. Distinctive features of this small butterfly are the white legs and antennae which contrast strongly with the dark body.

The Mountain Ringlet can be confused with the closely related Scotch Argus (Erebia aethiops) which is a somewhat larger dark butterfly which also has orange bands on the upperwings containing black eyespots and which is also found in the Scottish Highlands. However, the Scotch Argus flies somewhat later in the summer commencing about the 20 July but this overlaps with the latter part of the flight period of the Mountain Ringlet which can lead to mis-identification of the much rarer Mountain Ringlet.

Credit: Jim Asher

Credit: Jim Asher

Credit: Jim Asher

Life Cycle

The Mountain Ringlet is the UK's only truly montane species only being found above about 350 m and the remoteness of its habitat means this species is not well-studied. It has been suggested that it has a two year life cycle like some montane moths but while this has been demonstrated in captivity, it has not been confirmed in the field.

Eggs are laid singly in July on dead grass blades of its host plant, Mat-grass, or perhaps on mosses or sedges nearby. The larvae feed at night on Mat-grass tips and hide by day at the grass base and are therfore very difficult to study. It has been mooted that other grasses such as Sheep's Fescue and Common Bent may also be host plants.

The larvae hibernate amongst grass as third instar caterpillars during late August or September. After resuming feeding in the spring, pupation occurs in late May or June on the ground or in grass tussocks.

Flight Times

The flight period is short from late June to early August with marked differences in the peak from year to year. Adults only live a few days and their activity is highly dependant on temperature: in cooler conditions, flights are confined to sheltered streams or dry gullies rich in nectaring plants whereas in warmer conditions, adults may be found widely across south-facing hillsides.

Habitat & Distribution in SW Scotland

Distribution for 1995-2004

The South-West Scotland branch area is an important stronghold for the Mountain Ringlet with colonies in the Breadalbane hills in Stirlingshire, Ben Lomond in Dunbartonshire and in the mountains of Argyll. The remoteness of its habitat means it is certainly under-recorded and branch members are encouraged to get involved in surveys for this species (see Surveys 2008). In Scotland, the habitat is south-facing hillsides from 350 to 1000 m but further research is needed to understand the finer aspects of Mountain Ringlet ecology. Its host plant, Mat-grass is widespread and abundant on mountain hillsides but observations suggest that Mountain Ringlet prefer areas with abundant nectaring plants including Thyme, Tormentil & Heath Spotted Orchid such as sedge flushes and dry gullies which will also provide a warmer micro-climate within the cold mountain environment.

References

• Holland, J. (2000). Mountain Ringlet Species Action Plan. Scottish Agricultural College & Upland Working Group.
• Futter, K., Sutcliffe, R., Welham, D., Welham, A., Rostron, A., MacKay, J., Gregory, N., McCleary, J., Tait, T., Black, J. & Kirkland, P. 2006. Butterflies of South West Scotland. Argyll Publishing. (see Atlas page)
• Asher, J., Warren, M, Fox, R., Harding, P., Jeffcoate, G., Jeffcoate, S. 2001. The Millennium Atlas of Butterflies in Britain & Ireland. Oxford University Press.

Written by Andrew Masterman