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.