including the forest ringlet (Dodonidia helmsii) and Butler's ringlet (Erebiola butleri). Description The wingspan of the Percnodaimon imago can be between 35 and 55 mm, and its broad velvety wings are usually black or brown across the dorsal surface, sometimes with a purple reflection. Forewings have characteristic black and white circles inside a patch of brown at their distal ends. There is little sexual dimorphism: males and females are similar in appearance, with females a little larger. The row of large pale spots often found on the underside of the hindwings is more noticeable in females. Black mountain ringlets fly slowly in zigzag patterns, especially on a sunny day, taking advantage of thermals and often gliding in a "V" position."When disturbed this insect flies often with considerable rapidity and thus often eludes the net, so that the capture of a good series of specimens on a rugged mountain-slope is usually very exciting, if not actually dangerous work." —George V. Hudson (1928) Wing colour plays an important physiological role: the dark wings with a large surface area absorb sunlight and store heat, essentially acting like solar panels, an adaptation to the cool climate of the Southern Alps. The butterfly sits with its wings open and turned towards the sun, flying while the sun is shining and hiding amongst rocks when clouds intervene. At night they shelter deep in rocky crevices. Distribution The genus Percnodaimon is restricted to the dry eastern mountains in the South Island of New Zealand, on greywacke scree slopes and amongst rockfalls. It occurs at altitudes ranging from 800 to 2500 metres, up to 3100 m in the northern mountains of the South Island. Although the butterfly is less common below 1200 m, it can be found down to 800 m on valley floors and passes if the scree habitat is present. It can be quite common and even seasonally abundant in suitable habitat. Life cycle Ovum The adult female black mountain ringlet deposits her eggs atop stones on alpine slopes, rather than on a larval food plant. When the sun is out it heats the stone's exposed surface, incubating the eggs. This behaviour is unique among New Zealand butterflies and is only seen in a handful of butterfly species occupying the Himalayas and European Alps. The eggs are initially blue, eventually turning speckled and brown, which allows them to blend in with the stony background. About two