All the wings are pale ochreous; the fore-wings have a slender brown transverse line at the base, then a large loop-like marking from the costa, almost meeting a smaller, similarly looped marking from the dorsum; next a broad irregular dark brown band a little beyond the middle, considerably indented towards the termen; this is followed by a rather narrow pale band, and then by a narrow brown band, also indented towards the termen; there is a small oblique brown mark below the apex, and a terminal series of black dots.

The hind-wings have several faint dusky transverse lines near the base, a row of small spots near the termen, and a terminal series of minute black dots.

[1][8] As well as the type locality of Dunedin, the species has been found in the Dansey Ecological district and the Nevis Red Tussock Fen in Otago.

[5][11] This moth has been observed as frequenting tussock and scrubby areas that have the fern Polystichum vestitum present.

[11] The larvae of A. helias have been reared in captivity on forest herbs including Cardamine and Ranunculus species.