Revision of the New Zealand cave wētā genus Isoplectron Hutton (Orthoptera: Rhaphidophoridae), with synonymy of Petrotettix Richards and Setascutum Richards, and the description of a new genus Author Hegg, Danilo 34DFC18A-F53D-417F-85FC-EF514F6D2EFD Wētā Conservation Charitable Trust, 135 Blacks Road, Ōpoho, Dunedin 9010, New Zealand. danilo@wetaconservation.org.nz Author Morgan-Richards, Mary 48F2FB1A-4C03-477C-8564-5417F9739AE1 Wildlife & Ecology Group, Massey University, Private Bag 11 - 222, Palmerston North 4442, New Zealand. M.Morgan-Richards@massey.ac.nz Author Trewick, Steven A. 7A378EE1-BADB-459D-9BAA-7059A675F683 Wildlife & Ecology Group, Massey University, Private Bag 11 - 222, Palmerston North 4442, New Zealand. S.Trewick@massey.ac.nz text European Journal of Taxonomy 2024 2024-12-10 971 1 75 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2761/12643 journal article 10.5852/ejt.2024.971.2761 2118-9773 14451786 F82472D1-595D-4DB7-A463-513B94BE85D9 Genus Isoplectron Hutton, 1896 Isoplectron Hutton, 1896: 237 . Setascutum Richards, 1972: 163 . Syn. nov. Petrotettix Richards, 1972: 166 . Syn. nov. Isoplectron – Karny 1937: 229–230 , pl. 6 fig. 5. –– Ward 1997: 13–15 . –– Johns & Cook 2013: 1 . –– Hegg et al. 2022: 51–52 . Setascutum – Ward 1997: 13–15 . –– Johns & Cook 2013: 1 . Petrotettix – Ward 1997: 13–16 . –– Johns & Cook 2013: 1 . –– Hegg et al. 2022: 51 . Type species Isoplectron armatum Hutton, 1896 . Diagnosis A genus of small to mid-sized Rhaphidophoridae (adult body length typically between 9 and 13 mm ; up to 18 mm in the larger species), with hind tibiae armed above with two rows of linear spines that are very similar in size. These spines are fused to the shaft of the tibia and are never socketed or articulated. Fore femora always without apical spines; mid femora usually armed with one retrolateral spine at the apex. Male subgenital plate broadly speaking triangular, with an elongated central lobe; female subgenital plate bilobed. Upper valve of the ovipositor always serrated above. While some species of Isoplectron are morphologically very similar and are easily mistaken for one another, other species are morphologically and ecologically quite distinct. This makes it somewhat difficult to characterise the genus, yet some traits are common to all species. A detailed description of these common traits follows; individual species descriptions focus on those traits that differ among species. Etymology Not explained by Hutton. From the Greek ʻ Isos ʼ = ‘equal’, ʻ plectron ʼ = ʻplectrumʼ (probably referring to the dorsal spines on the hind tibiae, which are shaped like a plectrum). The hind tibiae are armed with spines that are equal in shape and size. Isoplectron is neuter gender. Description Adult MESUREMENTS . See Table 1 . Sexual dimorphism in body length, with females being larger than males by up to 10% in most but not all species. HEAD ( Fig. 11A–B ). Oval in shape. Eyes rounded, but with a straight inner edge facing the scapes of the antennae. Eye colour green, wholly or partially, in all species. Fastigium divided by a deep median groove; shaped like an isosceles triangle with a rounded pale patch in the middle when seen from the side. No visible sexual dimorphism in scapes of antennae or any other head-part. Labial and maxillary palps pale, of varying length, with moderately dense covering of hair. THORAX . Pronotum, mesonotum and metanotum all covered in dense, fine tomentum. A pale, thin median dorsal line is generally inconspicuous or absent (see Fig. 12A–I ). Lateral edges of pronotum with a pronounced rim. In dorsal view, the pronotum is up to 80% wider at the posterior end than at the anterior end ( Fig. 12A–I ). LEGS . Moderately long. Hind femora slender; sexual dimorphism evident, with all leg segments longer in males than in females in most but not all species. Coxae and trochanters generally of uniform pale colour. Fore and mid femora and tibiae may be uniform pale or variegated; hind legs variegated. Fore coxae with a pronounced lateral anterior spine. Fore tibiae approximately half of body length, and 10% longer in males than in females in most species; on average 5% longer than fore femora in both males and females. Fore femora without linear spines above or below, and always without apical spines. Fore tibiae armed below, generally with two linear spines on both anterior and posterior edge in all species. The number of apical spines on the fore tibiae varies by species. Mid legs 2% to 5% shorter than fore legs, otherwise with the same proportions in male and females. Mid femora without linear spines above or below, but usually armed with one retrolateral spine at the apex. A prolateral spine at the apex of the mid femur is always absent. Mid tibiae armed below, generally with two linear spines on both anterior and posterior edge in all species. Dorsal linear spines on the mid tibiae are rare but possible. The number of apical spines on the mid tibiae varies by species. Hind tibiae approximately of same length as body in females, up to 50% longer in males in most but not all species. Hind femora approximately 10% shorter than hind tibiae. Hind femora generally armed with few but at times very conspicuous linear spines below on both anterior and posterior edges. Hind tibiae armed with anything between 11 and 37 linear spines above (number varies both within and between species), of similar size, on both anterior and posterior edges ( Fig. 13A–I ). The spines are fused to the shaft of the tibia and are never socketed or articulated. The number of apical spines on the hind tibiae varies by species. Hind tarsi with four segments; first and second segments with a pair of spines on distal end. First and second tarsal segment may be armed or unarmed above, depending on species. ABDOMEN . Tergites always covered in dense, fine tomentum. Colour of tergites varies by species; a pale, thin median dorsal line is generally inconspicuous or absent (see Fig. 12A–I ). In some species, the seventh and eighth sternites are equipped with 3 to 5 very conspicuous protuberances, in females only (see Fig. 18G, J and Fig. 19A ). MALE TERMINALIA . Cerci between 10% and 25% of body length depending on species; pointed at apex, variable in colour, clothed in setae. The subgenital plate looks somewhat similar in all species, with an elongated median lobe; it is at least twice as long at centre as on the sides. Paraprocts armed with strong, stout spinules in most species. The difference in male terminalia between species is pronounced enough to provide one of the strongest characters for species level identification (see Figs 14–16 ). FEMALE TERMINALIA . Subgenital plate consists of two small, rounded lobes, separated by a gap in the middle. Ovipositor reddish-brown, moderately to strongly curved upwards at apex, terminating in a sharp point; approximately three quarters of body length in most species. Upper valve always serrated above, strongly so in some species; lower valve with 5 to 10 strong teeth at apex on ventral edge ( Figs 17–19 ). Nymph Generally look similar to adults. Due to the small size of the insects and the lack of developed terminalia, nymphs may be next to impossible to differentiate from their equivalents in Praecantrix gen. nov. or Neonetus . Table 2. Isoplectron Hutton, 1896 and Praecantrix gen. nov. Summary of Bayesian model results for length of insect body and of hind tibia as a function of sex, geographical coordinates (easting, northing in New Zealand Geodetic Datum 2000 map grid) and elevation (m a.s.l.). All models run in JASP ver. 0.17.1. Species for which sample size is too small for statistics are omitted. CI stands for credible intervals; for covariates these are only reported where they are significant.

Species	Measurements (mm)	Sample size 1	Bayesian Linear Mixed Model Fixed factor: Sex Random factor: Location	Bayesian Linear Regression Factor: Sex Covariates: Easting, Northing, Elevation
Isoplectron armatum armatum	Body	46	No sexual dimorphism 95% CI: - 0.34–0.93 mm	No effect of covariates
Hutton, 1896	Hind tibia	46	+ 2.5mm in ♂ 95% CI: 1.59–3.20 mm	No effect of covariates
Isoplectron armatum	Body	13	No sexual dimorphism 95% CI: -1.09– 0.99 mm	No effect of covariates
aciculatum Karny, 1937	Hind tibia	13	+ 3.2mm in ♂ 95% CI: 1.01–5.35 mm	No effect of covariates
Isoplectron pallidum Richards, 1972	Body	23	No sexual dimorphism 95% CI: -1.54– 1.40 mm	+ 0.13 mm per 100 m elevation 95% CI: 0.00 mm– 0.60 mm + 0.99mm per 100 km south 95% CI: 0.00 mm– 2.96 mm
Hind tibia	23	+ 1.2 mm in ♂ 95% CI: - 0.01–2.35 mm	+ 0.15 mm per 100 m elevation 95% CI: 0.00 mm– 0.60mm
Isoplectron serratum	Body	27	+ 1.2 mm in ♀ 95% CI: 0.1–2.37 mm	No effect of covariates
Richards, 1972	Hind tibia	27	+ 3.7 mm in ♂ 95% CI: 1.84–5.89 mm	No effect of covariates
Isoplectron ferratum	Body	18	No sexual dimorphism 95% CI: - 1.1–2.06 mm	No effect of covariates
sp. nov.	Hind tibia	18	No sexual dimorphism 95% CI: - 0.27–1.23 mm	No effect of covariates
Praecantrix silvatica	Body	23	+ 1.2 mm in ♀ 95% CI: 0.3–1.97 mm	No effect of covariates
gen. et sp. nov.	Hind tibia	23	+ 0.8 mm in ♀ 95% CI: 0.12–1.43 mm	No effect of covariates
Praecantrix saxicola	Body	10	+ 2.8 mm in ♀ 95% CI: 1.56–4.09 mm	Sample size too small
gen. et sp. nov.	Hind tibia	10	+ 1.8 mm in ♀ 95% CI: 0.06–3.42 mm	Sample size too small

1 For the number of males and females in each sample, refer to Table 1 . Fig. 10. Known distribution of cave wētā in the genera Isoplectron Hutton, 1896 and Praecantrix gen. nov. A–C . All of New Zealand. A . Isoplectron armatum Hutton, 1896 . Solid shapes indicate material collected as part of this study; empty circles indicate additional locations of material examined by Hutton (1896) . Shapes represent different subspecies: circle = Isoplectron armatum armatum Hutton, 1896 ; diamond = Isoplectron armatum aciculatum Karny, 1937 . B . Praecantrix silvatica gen. et sp. nov. Shapes represent different subspecies: dark green square = Praecantrix silvatica silvatica gen., sp. et subsp. nov.; light green diamond = Praecantrix silvatica lutea gen., sp. et subsp. nov. D . Map of North Island. E–J . Map of South Island. F . Isoplectron serratum ( Richards, 1972 ) comb. nov. Solid shapes indicate material collected as part of this study; empty diamonds indicate additional locations of material examined by Richards (1972) . Scale bars: 200 km. Distribution New Zealand , all of South Island; limited to southern regions in North Island ( Fig. 3 ).