Percnodaimon merula, the black mountain ringlet, is a satyrid butterfly in the family Nymphalidae. It is currently the only recognised species in the monotypic genus Percnodaimon, endemic to New Zealand, although there may be other undescribed species in the genus. The black mountain ringlet is notable for living exclusively in rocky areas of New Zealand's Southern Alps, usually above 1200 m. Its eggs are laid on rocks, its larvae feed on mountain Poa species, and it pupates under a stone. It has distinctive dark velvety wings and a zig-zag flight pattern over the scree slopes on which it lives.

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