The pupa is rather stout, light green, with the edge of the wing-case and the prominences formed by the back and palpi, edged with crimson and white. It is suspended by the tail to any firm object in the neighbourhood of the sedge.
The perfect insect appears in February. It frequents sunny glades in the birch forest, usually at considerable elevations above the sea-level. Mr. Helms informs me that he has seen specimens near Greymouth in October, and hence concludes that there are two broods in the year. The butterfly is very difficult to capture, as it has a most provoking habit of resting on the foliage of the birch-trees, just out of the collector's reach. I am unable to explain the object of the remarkable colouring of the under side of this insect, but it is probably protective, although in what way has yet to be discovered.
"Eyes glabrous. Club of antennæ abrupt." (Plate I., figs. 25, 26, and 27 neuration of _Erebia pluto_.)
"An extensive and essentially Alpine genus inhabiting the mountains of Europe, Asia, North America, and South Africa. Pupa unattached amongst stem bases of grass."--(Meyrick.)
(_Erebia pluto_, Fereday. _Erebia merula_, Hewitson, Ent. Mo. Mag. xii. 10 (1874). _Oreina othello_, Fereday, Trans. N. Z. Inst. viii. 302, 304, pl. ix. (1876). _Percnodaimon pluto_, Butl., Ent. Mo. Mag. xii. 153 (1876); Catalogue of N. Z. Butterflies, 10.)
(Plate XI., fig. 8 [M], 9 [F], 10 under side.)
This fine butterfly has occurred plentifully on many mountain-tops in the South Island, from Nelson to Lake Wakatipu. It has never been observed in the North Island.
The expansion of the wings of the male is 1¾ inches, of the female 2 inches. _On the upper side all the wings are a very rich bronzy-black. The fore-wings have a paler patch near the apex, containing two small, and three large black ocelli with white centres_; these ocelli are usually joined together. On the under side all the wings are considerably paler and greyer. The hind-wings have a series of pale spots near the termen, and a paler shade across the middle.
The insect varies chiefly in the number of ocelli. On the upper side of the fore-wings there are sometimes only four, the minute ocellus on the costa being absent, whilst occasionally a small extra ocellus appears below the normal series. On the under side this last-mentioned ocellus is very frequently, but not invariably, present. In some female specimens an extremely minute ocellus may be detected on the upper surface of the hind-wings near the termen. On the under side of the hind-wings in both sexes the series of pale terminal spots are often absent, and the general depth of the colouring varies considerably.