The larva feeds on a species of sedge (_Galinia setifolia_), which always grows abundantly in the birch forests, where the butterflies are found. When full grown the length of this caterpillar is about 1¼ inches. Its body is much attenuated at each end and rather stout in the middle; the head and tail are bifid; there are numerous straight, shallow, transverse wrinkles on each segment, especially towards the head. The colour is green, with a number of fine, paler and darker green, dorsal and lateral lines; the head and thirteenth segment are yellowish. The legs are very minute, and the prolegs of moderate size. It is extremely susceptible to the attacks of a Dipterous parasite. In fact, out of thirty larvæ kept by Mr. Hawthorne and myself, no less than 75 per cent. were thus destroyed. This larva feeds on the leaves of the sedge, eating out long notches parallel to the veins of the leaf. These notches are the best guides to follow in searching for the larva, as the colouring of the caterpillar renders its discovery amongst the food-plant extremely difficult. The larvæ should be looked for during the end of December or the beginning of January. 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. Genus 3.--EREBIA, Dalm. "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.) We have two species in New Zealand. {114}EREBIA PLUTO, Fereday. (_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.