The perfect insect appears in December and January, and frequents the overhanging banks of streams in densely wooded ravines, where it often occurs in the utmost profusion.
HYDRIOMENA PURPURIFERA, Fereday.
(Cidaria purpurifera, Fereday, Trans. N. Z. Inst. xvi. 119; Meyr., ib. 75.)
(Plate [VII]., fig. 12.)
This extremely pretty insect has been taken in the South Island at Mount Arthur, Mount Hutt, Castle Hill, Dunedin, and Lake Wakatipu.
The expansion of the wings is about 1 inch. The fore-wings are rather bright green; there is a darker area near the base, a very broad purplish-brown central band, with a large square projection on the middle of its outer edge; above this projection there is a very conspicuous white mark, bordering the central band; the remainder of the wing is green; there is a wavy white line near the termen, and an oblique bluish-black mark near the apex. The hind-wings are pale brownish-yellow.
This species is closely allied to Hydriomena rixata, but easily distinguished by its brighter green colouring, purplish central band with square projection, and broad white marking beyond the central band.
The perfect insect appears in December and January, and frequents forest at elevations of from 1,000 to 3,000 feet. It is found in drier situations than the preceding species, and is not confined to forest streams. It is common in certain localities, but is not nearly so generally distributed as Hydriomena rixata.
HYDRIOMENA SIMILATA, Walk.
(Cidaria similata, Walk. 1413. Cidaria timarata, Feld. cxxxii. 19. Cidaria similata, Meyr., Trans. N. Z. Inst. xvi. 76.)