Erebiola butleri, or Butler's ringlet, is an elusive New Zealand endemic butterfly, discovered in 1879 by John Enys at the alpine pass at the head of the Rakaia River. It is the only member of the genus Erebiola. Erebiola is derived from Erebus, the ancient Greek world of darkness between Earth and Hades, while the specific name, butleri, was after Arthur Gardiner Butler of the British Museum who played a major role in early descriptions of New Zealand butterflies. Its Māori name is pepe pouri, which means dark moth, and shares the name with the black mountain ringlet and the forest ringlet butterfly. Description Butler's ringlet has a wingspan of 35–43 mm, with a 40 mm average for males and a 37 mm average for females. Both males and females are smoky brown, though males tend towards the richer browns while the females tend towards the paler browns. The underside of the hindwing has wedge-shaped silvery-white marks. Both the underside and the topside of the wings have eyespots at the distal-most ends, surrounded by reddish-brown shading. There is variation between individuals in the number of eyespots, the extent of the reddish-brown colouring around the eyespots, and the silvery-white markings on the undersides of the hindwings. The egg is ivory with vertical ribbing. The larvae is similar coloured from head to tail, being yellow brown with dark and light lateral striping. A fully grown larvae is roughly 20 mm long. The pupa is grey and cream with fine black spotting along the abdomen, changing to a brown on the rest of the body. The style of pupation is unknown. Life stages The egg is laid singularly on a shrub and hatches after 14 days. The larvae grows from 3 mm to 20 mm over an unknown length of time, before pupating. Pupation lasts about 21 days. It is unknown how long adult E. butleri live for. Distribution Butler's ringlet is confined to the subalpine zone in the South Island. It has been identified at only a few sites along the main divide of the Southern Alps. It favours subalpine terraces at altitudes of 900 to 1300 m in areas of snow-tussock with Hebe and Dracophyllum shrubs. Its preferred locations are often damp, almost boggy, or next to mountain lakes. It is very difficult to find even in areas where it has previously been seen, and so little is known about its