WĒTĀ

Two new species of ground wētā have been described in the latest work by Steve Trewick and Mary Morgan-Richards of Massey University, published in Zootaxa on 29 July 2025. Both species are placed in Anderus, a genus that was only designated last year (Trewick et al. 2024).

Anderus pipiwai is a forest wētā currently known from central-northern Fiordland and from South Westland, between the Spey River in the south and Franz Josef Glacier to the north. The boundaries of the species’ geographic distribution are not fully known. The name pīpīwai means ‘damp’ or ‘swampy’ in Te Reo Māori and is an apt descriptor for the region the wētā lives in. The insect is of uniform dark colour on head and body and looks most similar to Anderus nox from the Tasman region and North Island, although it is substantially larger than the latter species. It is however most closely related to Anderus fiordensis, whose distribution range it overlaps. The similarity in habitus between Anderus pipiwai and A. nox is a case of convergent evolution in two species that occupy similar habitats. Both are ground-dwelling insects found in leaf litter on the forest floor; the uniform black colour maximizes camouflage and concealment from visual predators.

Anderus rakiura is endemic to Stewart Island / Rakiura, where it occupies all habitats from sea level to the open tops above tree line. It is the only species in the genus Anderus known from the island, where the only other known ground wētā is the alpine Hemiandrus focalis. The species is most closely related to Anderus subantarcticus from Snares Islands / Tini Heke. It is dark dorsally but has conspicuous cream-coloured patches on the sides of the head and of all thoracic segments.

Are the two new species recent discoveries?

No, they are not. Both taxa were identified by entomologist Peter Johns in his work on Hemiandrus (2001) and were given tag names. Anderus pipiwai was referred to as Hemiandrus ‘madisylvestris’, whereas Anderus rakiura was Hemiandrus ‘saxatilis’. These tag names have been consistently used in scientific literature on New Zealand wētā since then; Anderus pipiwai for instance features as a component in the diet of stoats in Fiordland (Smith et al. 2005). The tag names ‘madisylvestris’ and ‘saxatilis’ are also used to refer to the two species in the latest NZTCS assessment of New Zealand Orthoptera (2022), where both are listed ‘Not Threatened’.

What is a tag name?

A tag name is an informal name that exists outside of the International Codes of Nomenclature and is designed to indicate an entity that is believed to be a separate species. It is usually written between inverted commas, in regular characters (not italics). The purpose of a tag name is to act as a temporary label for a putative species until a formal assessment can be made (Leschen et al. 2009). In this case, it has taken nearly 25 years for Hemiandrus ‘madisylvestris’ and H. ‘saxatilis’ to be formally recognized as valid species from the time when they were first identified.

It should be noted that taxa that are assigned a tag name do not automatically attain species status. It is a frequent occurrence for a tag name to be eventually discarded, if it is shown that the entity it refers to is a species that is already described. In the latest NZTCS assessment of New Zealand Orthoptera (2022) for instance, 16 putative taxa that had previously been listed on the basis of the work by Johns (2001) were rejected and discarded as they do not represent any known described or undescribed species.