Hydriomena iolanthe

This species was first described by George Hudson in 1939 using a female specimen collected at Lake Harris by F. S. Oliver in January 1918.[2][3] Due to the single specimen being damaged and lacking antennae, Hudson was uncertain of the generic position of the species.[2] He therefore named the species Hydriomena (or Xanthorhoe) iolanthe.[2] The illustration is labelled Hydriomena? iolanthe.[2] The classification of New Zealand endemic moths within the genus Hydriomena is regarded as unsatisfactory and in need of revision.[4] As such this species is currently also known as Hydriomena (s.l.) iolanthe.[5][4] This species may prove synonymous as the hototype specimen has been lost and it is possible it is a European species that was mislabelled.[6][7] It was listed in the New Zealand Inventory of Biodiversity as nomen dubium.[5]

Hudson described the species as follows:[2]

The expansion of the wings is 7⁄8 inch (22 mm.). The forewings have the apex rather obtuse and the termen slightly oblique; there is a deep reddish-brown basal patch followed by a rather indistinct pale transverse line; the subbasal area is orange-brown, followed by a narrow whitish-ochreous band from 1⁄4 of costa to 1⁄3 of dorsum; this band is abruptly bent outwards just below costa and contains a fine blackish line; the median band is dull red, slightly purplish tinged; it contains a small black discal dot and two fine wavy blackish lines enclosing an irregular central area; the outer edge of the median band is finely waved, with slight irregular projections below costa, and a more evident rounded projection in disc; the dorsal third of the median band is much narrower; beyond the median band the ground colour of the wing is pale brownish-ochreous; there are two fine wavy blackish lines immediately outside the median band; a conspicuous yellowish-brown patch on the costa before apex and a blackish-brown patch below this; a very wavy paler subterminal line and a series of minute terminal marks. The hind-wings are dull whitish-ochreous, with numerous pale brownish-ochreous transverse lines and terminal band, some of the lines become blackish towards dorsum; there is a series of minute terminal dots; the cilia of all the wings are dull brownish-ochreous.[2]

This species is indigenous to New Zealand.[3] This species is found on the Otago Lakes Fiordland border.[8] It is only known from the type locality of Lake Harris on the Routeburn Track.[8]

This species is on the wing in January.[2]

It has been hypothesised that the host of the larvae of H. iolanthe is possibly a species of Coprosma.[8] The reasoning behind this hypothesis is that the illustration of the species resembles an Austrocidaria and Coprosma plants are the host for species in that genus.[8]

This species has been classified as having the data deficient conservation status under the New Zealand Threat Classification System.[1] Hudson's description was based on a single specimen which is now lost.[8][5] The illustration by Hudson has not been matched to any known endemic or adventive species.[8][5]