Mountain Beech Flat Moth

The larvae of this species, which has sixteen legs, was described by Hudson as follows:

rather stout, cylindrical, tapering behind; pale whitish-green or yellowish-green, generally more greyish-green on the sides; the dorsal line is broad, irregular, dark brownish-purple, sap-green or yellowish-green mixed with reddish-ochreous and bisected by a slender, interrupted, whitish line; the lateral line is sap green or obsolete; the sub-spiracular line is slender, interrupted, dark brownish purple or faintly pinkish; the spots are small, shining, dark brown; the head is ochreous-brown or yellowish green; the second segment is greener than the body, blackish marbled with pale ochreous, the larva generally being remarkably variable. Butler described the adults of the species as follows:

Primaries flesh-colour, costal margin blood red, the same colour also extending for a short distance down the fringe, which is throughout rather darker than the body of the wing; secondaries white, slightly tinted with flesh-colour at the borders; thorax flesh-coloured; palpi and femora and tibiae of anterior legs carmine : wings below nearly as above, excepting that the secondaries show three or four apical marginal dark grey spots; body below white. Expanse of wings 11 lines. Hudson noted that there is variation in the colour of the forewings of this species. …

This species is endemic to New Zealand. It has been found near Wellington in the North Island, the tableland of Mount Arthur, in the Canterbury region, Arthur's Pass and at Lake Wakatipu in the South Island. It is more common in the South Island than in the North Island.

The female moth can lay up to 300 eggs and she deposits them individually on the underside of native beech leaves. There is only one generation a year. The larvae feed on those tree leaves from winter to early summer. The larvae make a web of silk and leaf hairs camouflaging themselves amongst the leaves, and proceed to feed from this shelter. It pupates amongst dead leaves making a slight cocoon around the short, stout, pale green and brown pupa. The adult moth emerges from the pupa after approximately fourteen days. The adults are on the wing from January to April. They are a day flying moth and when inactive rest on beech leaves, which their appearance mimics. The adult moths are not attracted to light.