Scotch argus

Taxonomy

Subspecies include:

Distribution and habitat

Erebia aethiops is widespread in the Palaearctic ecozone, including most of Europe, the Alps and Apennines, Balkans, Asia Minor, the Urals, Caucasus, and Sajan. English colonies are found at Arnside Knott and Smardale Gill both in Cumbria. This species is found in most of northern Scotland, and in western areas in south Scotland. In Europe and Russia, these butterflies prefer the edge of the pine forests and tall damp grassland in hills and mountains up to 2400 m.

Description

Erebia aethiops has a wingspan of 42–46 mm. Antennae are clavate. The background color of the wings varies from dark brown to black brown, with reddish yellow bands, black eye spots with white pupils and greyish wing fringes, weakly chequered in the females. On the forewing there are 3-4 eye spots, usually two apical plus a third detached, while on the hindwings there are 4-5 spots.

The underside of the hindwings shows a whitish or cream banding but there is a slightly marked sexual dimorphism. In Scotland, the sub-species caledonia has a narrower reddish yellow band and never contains more than three small eye spots. Three black spots are present on each hindwing. The egg is oval-shaped, with 20 to 28 longitudinal ribs. The mature caterpillar is yellow-brown, with a brown head. The pupae are yellow-brown and relatively short and compact, reaching a length of 12.5–124.5 millimetres (0.49–4.90 in).

This species is rather similar to Erebia ligea, but the fringes on the edges of the upper side of the wings are more light gray, while in E. ligea they are white.

Biology

This species is univoltine. Adults fly from June to August. The eggs are laid singly on the leaves of grass. The larvae hatch after 2 weeks. The hibernating larva is reported to feed on Agrostis, Dactylis, Poa annua, Bromus erectus and other grasses. In Scotland the main host plants are Purple Moor-grass (Molinia caerulea) and Blue Moor-grass (Sesleria caerulea).