Common Brassy Ringlet

Erebia cassioides/arvernensis


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Erebia cassioides

Switzerland, August 2013

Erebia cassioides

Switzerland, August 2013

Erebia arvernensis

Switzerland, July 2011

Mating pair, July 2005

Val d'Aran, Spain, July 2000

Erebia cassioides

Switzerland, July 2012

Switzerland, some time pre-2000 ...

Erebia cassioides distribution

Distribution

The subspecies of common brassy ringlet found in the western Alps and Spain, arvernensis, is treated by some authors as a good species, on the basis of molecular data, while others maintain this is unjustified. Somewhat arbitrarily, I choose to treat it as a subspecies here. All the pictures above, mostly from Switzerland but some from Spain, illustrate arvernensis. It is a common enough butterfly in the mountains near me (Villars-Gryon), though replaced by the Swiss brassy ringlet in many parts of Switzerland - as a rule, a given site will host just one species of brassy ringlet, though there are exceptions to this. I encounter common brassy ringlets particularly on paths, where usually lone individuals are found taking minerals or just occasioally basking, and find them very wary of humans. I have never seen large groups, as is common with some other Erebia, or had them sit on my clothing or backpacks.

The male has brassy reflections on the upperside of the wings - not really caught in the few upperside photos I have. This is much less evident in females. The silvery grey underside separates common brassy ringlet from all other Erebia except the other brassy ringlets and the dewy ringlets. The latter have less of a 'coffee stain' on the underside hindwing and look quite different from above. To confirm common brassy ringlet, look for strong upperside markings, with a prominent row of submarginal eyespots on the hindwing, circled in reddish, and a pair of touching eyespots on the forewing, also set in reddish. In Swiss brassy ringlet the forewing spots are discrete, while the hindwing spots are absent or vestigial. In de Lesse's brassy ringlet the forewing spots are separated by a hair's breadth and there are small but distinct spots on the hindwing. In the Spanish and Pyreneen brassy ringlets, the forewing spots are conflated into one twin-pupilled spot.

The butterfly is found on grassy slopes from 1600m to 2600m (where it overlaps with de Lesse's brassy ringlet). The principle foodplant is sheep's fescue. Like the Swiss brassy ringlet, but unlike de Lesse's brassy ringlet, the caterpillars hibernate just once, completing their development in one seasonal cycle. The adults fly from the end of June through to the beginning of September.