Isoplectron virgatum, Hegg & Morgan-Richards & Trewick, 2024

Hegg, Danilo, Morgan-Richards, Mary & Trewick, Steven A., 2024, 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, European Journal of Taxonomy 971, pp. 1-75 : 47-48

Isoplectron virgatum sp. nov.

urn:lsid:zoobank.org:act:CF2E5537-FF7B-4C16-9236-6A00D079407A

Figs 3 , 8 , 10I , 12G , 13G , 15G–I , 18G–I , 23A

Diagnosis

A small insect, pale throughout, with six to eight longitudinal stripes on the back. A retrolateral spine at the apex of the mid femur is usually absent.

Very similar to I. parallelum sp. nov. and to Talitropsis poduroides (Walker, 1871) in morphology and habitat use, but geographically separated from these two species, which are confined to North Island. It can be mistaken for striped morphs of I. ferratum sp. nov., although the latter species is arboreal and is always armed with a retro-lateral spine at the apex of the mid femur, a trait that is generally absent in I. virgatum sp. nov.

Isoplectron virgatum sp. nov. could be confused with a small, undescribed species in the genus Notoplectron , which inhabits the southern regions of the South Island’s West Coast. This species, however, appears to prefer grasslands in the low alpine zone, whereas I. virgatum is mainly a low elevation species. Notoplectron also has a smooth upper valve of the ovipositor and macroscopically different male terminalia.

Etymology

‘ Virgātus ’ (adj.) is Latin for ‘striped’.

Material examined (see also Supp. file 1: Table S7)

Holotype

NEW ZEALAND • ♂, adult; Buller (BR), Ces Clarke Hut, Paparoa Range; 42.29007° S, 171.39307° E; 900 m a.s.l.; 6 Apr. 2019; D. Hegg leg.; on Phormium leaf; night search + insect net; NMNZ AI.071894.

Paratype

NEW ZEALAND • 1 ♀, adult; same data as for holotype; GenBank: PP155107; NMNZ AI.071895 .

Other naterial

NEW ZEALAND – Fiordland (FD) • 1 ♀; Cleft Creek, Hollyford Valley ; 44.64813° S, 168.10538° E; 100 m a.s.l.; 9 Jan. 2023; J. Jack leg.; in native forest; photograph only; iNaturalist 146558750 . – Westland (WD) • 1 ♀; Jackson Bay ; 43.97° S, 168.61° E; 80 m a.s.l.; 1 Nov. 2019; D. Hegg leg.; on tree fern; night search + insect net; GenBank: PP155105; MPN CW4666 • 1 ♂; Awatuna, Hokitika ; 42.64905° S, 171.06228° E; 40 m a.s.l.; May 2012; B. Taylor-Smith leg.; GenBank: PP155104; MPN CW2014 • 1 ♂; same data as for preceding; GenBank: PP155102; MPN CW2016 • 1 ♂; same data as for preceding; MPN CW2009 • 1 nymph; same data as for preceding; MPN CW2013 . – Buller (BR) • 1 ♂; Bob’s Hut, Matakitaki River West Branch; 42.22528° S, 172.48754° E; 840 m a.s.l.; 6 Jan. 2021; D. Hegg leg.; on Astelia leaf; night search + insect net; GenBank: PP155101; MPN CW5394 • 1 ♀; same data as for preceding; MPN CW5395 • 1 ♀; same data as for holotype; MPN CW4420 • 1 nymph; Truman Track, Punakaiki ; 42.09430° S, 171.34349° E; 50 m a.s.l.; 6 Dec. 2018; D. Hegg leg.; on Astelia leaf; night search + insect net; GenBank: PP155100; MPN CW4228 . – Nelson (NN) • 1 nymph; Granity Pass, Mt Owen ; 41.52327° S, 172.56349° E; 1200 m a.s.l.; 9 Jan. 2019; D. Hegg leg.; on Aciphylla flower; night search + insect net; GenBank: PP155106; MPN CW4290 • 1 ♀, 1 nymph; same data as for preceding; MPN CW4289 , CW4291 • 1 ♂; Cave Brook, Gouland Downs ; 40.89153° S, 172.35449° E; 630 m a.s.l.; 4 Feb. 2018; D. Hegg leg.; on Astelia leaf; night search + insect net; GenBank: PP155099; MPN CW3776 • 1 ♀; same data as for preceding; MPN CW3794 • 1 nymph; same data as for preceding; MPN CW3775 • 1 ♂; Heaphy River, Kahurangi NP; 40.983° S, 172.114° E; 20 m a.s.l.; 20 Feb. 2023; D. Hegg leg.; on Coprosma shrub; night search + insect net; GenBank: PP155103; MPN CW5622 .

Description

MEASUREMENTS. See Table 1. Body length approximately 11 mm in both males and females.

HEAD. Vertex pale with four brown lines running from the fastigium to the anterior margin of the pronotum, two above the eyes and two near the centre. Dark streaks run from the posterior margin of each eye to the pronotum, resembling the temples in a pair of sun-glasses. Frons, clypeus and labrum pale, with two faint, vertical dark stripes below the scapes of the antennae. Scapes and pedicels variegated; all other segments of the antennae pale.

THORAX. Pale with brown dorsal lines running along the length of the thorax and continuing into the abdomen ( Fig. 12G ).

LEGS. Relatively short, without sexual dimorphism. The hind tibiae are on average 95% of body length in both males and females. Fore and mid femora unarmed at the apex, although a retro-lateral apical spine on the mid femur may be present on rare occasion. Hind femora armed with one to three retrolateral and prolateral ventral linear spines, the retrolateral ones being larger. Fore tibiae armed with two pairs of ventral linear spines, and with one pair of ventral apical spines. A retrolateral dorsal spine at the apex of the fore tibia is present in 50% of examined specimens. Mid tibiae armed with two pairs of ventral linear spines, one pair of ventral spines and one retrolateral dorsal spine at the apex. A prolateral dorsal spine at the apex of the mid tibia is always absent. Hind tibiae armed with about 20 dorsal linear spines (min 16, max 24) on both the anterior and the posterior edge ( Fig. 13G ). Hind tibiae armed at the apex with two ventral apical spines, two dorsal apical spines and two dorsal sub-apical spines; the dorsal apical spines are largest. Ventral sub-apical spines are always absent. First and second segments in hind tarsi always unarmed except at the apex.

ABDOMEN. Tergites pale, with dorsal brown stripes running longitudinally along the whole length of the insect from the pronotum to the terminalia ( Figs 12G and 23A ). In females only, the seventh sternite is equipped with two ventral protuberances; the eighth sternite with three ventral protuberances ( Fig. 18G ).

MALE TERMINALIA. Suranal plate trapezoidal with conspicuous hair tufts on the two posterior corners. The posterior margin can be either straight ( Fig. 15G ) or deeply notched. Subgenital plate pear-shaped; covered in sparse, thin tomentum except near the base on the sides, which are glabrous; with a pronounced keel along its whole length ( Fig. 15H ). Cerci on average 20% of body length, covered in sparse, mostly short hair; tapering gradually along their whole length and ending with a blunt tip at the apex. Styli tapering and not reaching to the apex of the subgenital plate. Paraprocts with parallel sides, tapering to a sharp tip only near the apex; glabrous except for a single row of spinules near the interior margin ( Fig. 15G ).

FEMALE TERMINALIA. Subgenital plate consists of two bulging, rounded lobes, joined at the base and diverging at the apex; glabrous on the inner surface, covered in stout hair on the outer surface ( Fig. 18G ). Ovipositor on average three quarters of body length; curving gently upwards from the base to the apex; lower valve with 8 to 10 teeth below at the apex; dorsal surface of upper valve serrated in distal third ( Fig. 18H–I ).

Distribution and habitat

Isoplectron virgatum sp. nov. is mainly found on the elongated leaves of shrubs in the genera Phormium J.R.Forst. & G.Forst. and Astelia Banks & Sol. ex R.Br. , where the insect’s habitus blends in with the leaf’s longitudinal nervature. Distributed along the West Coast of South Island from Fiordland to Kahurangi ( Fig. 10I ).

Figures

Fig. 3. A. Phylogenetic relationships of six genera of New Zealand Rhaphidophoridae Walker, 1869 inferred from whole mitochondrial genome sequences using Maximum Likelihood approach and 1000 bootstraps. B. Map of New Zealand, showing locations of specimens of Isoplectron Hutton, 1896 and Praecantrix gen. nov. used in phylogenetic analyses (Figs 6–7). Colours correspond to different genera: red = Isoplectron; green = Praecantrix. Two letter codes indicate the New Zealand entomological regions (Crosby et al. 1998). These codes are reported in the Material examined section for each species.

Fig. 8. Gene tree for the eight morphologically identified species of Isoplectron Hutton, 1896 using Maximum Likelihood analysis of ~850 bp of mtDNA (COI) from 86 specimens. Node support labels are the result of 1000 ML bootstrap replicates.

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.

Fig. 12. Dorsal view of cave wētā in the genera Isoplectron Hutton, 1896 and Praecantrix gen. nov. A–I. Isoplectron. A. I. armatum armatum Hutton, 1896, adult ♂. Parsons Bush, Lake Ōhau (MPN CW5123). B. I. armatum aciculatum Karny, 1937, adult ♀. Ohakune (MPN CW5644). C. I. bicolor sp. nov., adult ♂. Mt Arthur Tablelands (MPN CW3760). D. I. serratum (Richards, 1972) comb. nov., adult ♂. The Gap, Torlesse Range (MPN CW3182). E. I. maculatum sp. nov., holotype, adult ♂. Middle Mt Peel, South Canterbury (NMNZ AI.071892). F. I. ferratum sp. nov., holotype, adult ♂. Cave Brook, Gouland Downs (NMNZ AI.071896). G. I. virgatum sp. nov., adult ♀. Cave Brook, Gouland Downs (MPN CW3794). H. I parallelum sp. nov., adult ♀. Ahumairangi Town Belt, Wellington (MPN CW5598). I. I. pallidum (Richards, 1972) comb. nov., adult ♂. Mt Kyeburn, Danseys Pass (MPN CW3456). J–L. Praecantrix. J. P. silvatica silvatica gen., sp. et subsp. nov., adult ♂. Mt Arthur Hut (MPN CW5390). K. P. silvatica lutea gen., sp. et subsp. nov., adult ♂. Peel Forest (MPN CW4968). L. P. saxicola gen et sp. nov., holotype, adult ♂. Mt Wakefield (NMNZ AI.071904). Scale bar: 10 mm.

Fig. 13. Left hind tibia of cave wētā in the genera Isoplectron Hutton, 1896 and Praecantrix gen. nov., adult ♂, dorsal view. A–I. Isoplectron. A. I. armatum armatum Hutton, 1896. Parsons Bush, Lake Ōhau (MPN CW5123). B. I. armatum aciculatum Karny, 1937. Ohakune (MPN CW 5646). C. I. bicolor sp. nov., holotype. Cave Brook, Gouland Downs (NMNZ AI.071889). D. I. pallidum (Richards, 1972) comb. nov. Duffers Saddle, Old Woman Range (MPN CW5385). E. I. serratum (Richards, 1972) comb. nov. The Gap,Torlesse Range (MPN CW3182).F. I. maculatumsp. nov., holotype. Middle Mt Peel, South Canterbury (NMNZ AI.071892). G. I. virgatum sp. nov. Cave Brook, Gouland Downs (MPN CW3776). H. I. ferratum sp. nov., holotype. Cave Brook, Gouland Downs (NMNZ AI.071896). I. I. parallelum sp. nov. Ahumairangi Town Belt, Wellington (MPN CW5569). J–K. Praecantrix J. P. silvatica lutea gen., sp. et subsp. nov. McLean Falls, Catlins Forest (MPN CW3901). K. P. saxicola gen et sp. nov., holotype. Mt Wakefield (NMNZ AI.071904). Scale bar: 5 mm.

Fig. 15. Adult male terminalia of cave wētā in the genus Isoplectron Hutton, 1896. Left column: dorsal view; central column: ventral view (subgenital plate); right column: lateral view. A–C. I. serratum (Richards, 1972) comb. nov. The Gap, Torlesse Range (MPN CW3182). D–F. I. maculatum sp. nov., Middle Mount Peel, South Canterbury. D–E. MPN CW5638. F. MPN CW5640. G–I. I. virgatum sp. nov., Heaphy River, Kahurangi NP (MPN CW5622). J–L. I. ferratum sp. nov., Cave Brook, Gouland Downs, Kahurangi NP. J–K. Holotype (NMNZ AI.071896). L. MPN CW4953. Scale bars: 1 mm.

Fig. 18. Adult female terminalia of cave wētā in the genus Isoplectron Hutton, 1896. Left column: subgenital plate; central and right columns: ovipositor. A–C. Isoplectron serratum (Richards, 1972). Kahutara Saddle, Seaward Kaikōura Range (MPN CW5555). D–F. I. maculatum sp. nov. Middle Mount Peel, South Canterbury (MPN CW5642). G–I. I. virgatum sp. nov., paratype. Ces Clarke Hut, Paparoa Range (NMNZ AI.071895). J–L. I. ferratum sp. nov., paratype. Mt Stokes, Marlborough Sounds (NMNZ AI.071897). Scale bars: 1 mm.

Fig. 23. Live Isoplectron Hutton, 1896 and Praecantrix gen. nov. in their natural habitats. A. Isoplectron virgatum sp. nov., adult ♀ on Astelia Banks & Sol. ex R.Br. leaf. Bob’s Hut, Matakitaki River. B. Isoplectron ferratum sp. nov. in black beech Fuscospora solandri (Hook.f.) Heenan & Smissen tree canopy. Cave Brook, Gouland Downs, Kahurangi NP.C. Isoplectron parallelum sp. nov., adult ♀ on flax Phormium tenax J.R.Forst. & G.Forst. flower. Wellington. D. Praecantrix saxicola sp. nov., adult ♀. Mt St Bathans, Central Otago. E. Praecantrix silvatica silvatica gen., sp. et subsp. nov. adult ♀. Mt Arthur Tablelands, Kahurangi NP. F. Praecantrix silvatica lutea gen., sp. et subsp. nov. adult ♀. Hinau Track, Kaikōura.