Review of the endemic New Zealand genus Arctesthes Meyrick (Lepidoptera, Geometridae, Larentiinae), with descriptions of two new range-restricted species

The genus Arctesthes Meyrick (Geometridae: Larentiinae: Xanthorhoini), endemic to the South Island of New Zealand, is revised. Four species are recognised, including two new species, as follows: Arctesthes catapyrrha (Butler, 1877), A. siris (Hudson, 1908), A. titanica sp. nov. and A. avatar sp. nov. All except A. catapyrrha are restricted to subalpine and alpine localities. Adults and genitalia are fully described and illustrated for all species; larvae of A. catapyrrha are also briefly described and illustrated. Only Arctesthes catapyrrha is widespread; A. siris is restricted to a few mountain ranges of Central Otago; A. titanica is only known from two wetland localities in the Von Valley of the Otago Lakes district, and A. avatar is only known from a few wetlands in a restricted area of north-west Nelson. The two new species are considered of very high priority for conservation