Isoplectron serratum ( Richards, 1972 ) 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 : 41-44

Isoplectron serratum ( Richards, 1972) comb. nov.

Figs 3 , 7–8 , 10F , 12D , 13E , 15A–C , 18A–C , 20C , 22C–F

Petrotettix serratus Richards, 1972: 166–169 , fig. 7.1–7.6, table 4.

Petrotettix spinosus Richards, 1972: 169–170 , fig. 8.1–8.3. Syn. nov.

Petrotettix cupolaensis Richards, 1972: 170–171 , fig. 9.1–9.3. Syn. nov.

Petrotettix nigripes Richards, 1972: 171–174 , fig. 10.1–10.6, table 5. Syn. nov.

Petrotettix serratus – Johns 1977: 325. –– Hegg et al. 2019: 42; 2022: 21.

Petrotettix spinosus – Johns 1977: 325.

Diagnosis

A relatively large insect with very long legs in males and variable coloration in adults, ranging from chequered yellow/ black to mottled grey / brown. Nymphs are a dull, dark green.

Isoplectron serratum is closely related to I. maculatum sp. nov., from which it can only be differentiated by examination of the male terminalia. The two species, however, are allopatric, their distribution ranges being separated by the Rangitata River.

In the western part of its distribution range, I. serratum shares the habitat with Pharmacus montanus Pictet & de Saussure, 1893 . It is most easily differentiated from the latter by the long, slender legs, the presence of dorsal linear spines on the first two segments of the hind tarsi and the serrated upper valve of the ovipositor.

In the Kaikōura Ranges and in North Canterbury, I. serratum is sympatric with Pleioplectron rodmorrisi Hegg et al., 2019 . The latter species, however, is unmistakable with its red-orange legs and antennae, purple-black back and a bold dorsal yellow median line.

Etymology

‘ Serrātus ’ (adj.) is Latin for ‘serrated’, ‘toothed like a saw’. While Richards (1972) did not explain her choice for the name, it seems most likely that it refers to the upper valve of the ovipositor, which is strongly serrated in the distal half.

The genus name Petrotettix is gender masculine ( Richards, 1972). The insect was thus originally named Petrotettix serratus . Isoplectron however is gender neuter. The declension of the species name therefore becomes serratum , as per article 34.2 in the International Code of Zoological Nomenclature ( ICZN 1999).

Material examined (see also Supp. file 1: Table S5 and Figs S7–S 10 )

Holotype

NEW ZEALAND • ♂, adult; Nort Canterbury (NC), Mt Binser, Cass ; 43.038° S, 171.857° E; 1000– 1200 m a.s.l.; 24 Feb. 1963; P. Johns leg.; among scree; CMNZ 000223 .

Paratype

NEW ZEALAND • 1 ♀, adult; Marlborough (MB), Mt St Patrick, St James Range ; 42.439° S, 172.748° E; 1200 m a.s.l.; 30 Oct. 1962; P. Johns leg.; among scree; CMNZ 000224 .

Other material

NEW ZEALAND – Mid Canterbury (MC) • 1 ♀, holotype of Petrotettix spinosus ; Hamilton Peak, Craigieburn Range ; 43.123° S, 171.690° E; 1500–1800 m a.s.l.; 15 Dec. 1968; R. Watson leg.; on rocky ridge; CMNZ 000219 • 2 ♂♂; Mt Somers ; 43.60777° S, 171.36341° E; 1300 m a.s.l.; 12 Dec. 2020; D. Hegg leg.; on rock bluffs; night search + insect net; MPN CW5583 , CW5584 • 1 ♀; same data as for preceding; MPN CW5585 • 1 ♂; Round Hill Creek, Taylor Range ; 43.43186° S, 171.29781° E; 1450 m a.s.l.; 4 Dec. 2016; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155132; MPN CW3188 • 3 ♂♂; same data as for preceding; MPN CW3189 , CW3190 , CW3193 • 2 ♀♀; same data as for preceding; MPN CW3191 , CW3192 • 1 ♂; Mount Ida ; 43.22° S, 171.53° E; 1500 m a.s.l.; 3 Dec. 1999; collector unknown; MPN CW178 B • 1 ♀; same data as for preceding; MPN CW178 A • 1 ♂; Hamilton Peak, Craigieburn Range ; 43.11746° S, 171.68554° E; 1750 m a.s.l.; 12 Feb. 2017; D. Hegg leg.; on rocky ridge; night search + insect net; GenBank: PP155143; MPN CW3301 • 1 ♀; same data as for preceding; GenBank: PP155141; MPN CW3306 • 1 nymph; same data as for preceding; GenBank: PP155142; MPN CW3274 • 9 nymphs; same data as for preceding; MPN CW3267 to CW3273 , CW3275 , CW3276 • 1 ♀; The Gap, Torlesse Range ; 43.25649° S, 171.78426° E; 1440 m a.s.l.; 20 Nov. 2016; D. Hegg leg.; on rocky outcrop; night search + insect net; GenBank: PP155144; MPN CW3185 • 2 ♂♂; same data as for preceding; MPN CW3182 , CW3186 • 3 ♀♀; same data as for preceding; MPN CW3183 , CW3184 , CW3187 • 1 ♂; Mid Hill, Black Range ; 43.06201° S, 171.58003° E; 1660 m a.s.l.; 18 Dec. 2021; D. Hegg leg.; on rocky ridge; night search + insect net; MPN CW5363 • 1 ♀; same data as for preceding; MPN CW5362 . – North Canterbury (NC) • 1 ♀; Spider Web, Organ Range ; 42.68837° S, 172.502947° E; 1670 m a.s.l.; 20 Dec. 2016; D. Hegg leg.; on rocky outcrop; night search + insect net; GenBank: PP155145; MPN CW3236 • 4 ♂♂; same data as for preceding; MPN CW3238 to CW3241 • 1 ♀; same data as for preceding; MPN CW3237 . – Buller (BR) • 1 ♀, holotype of Petrotettix cupolaensis ; Cupola Basin, Travers Range ; 41.980° S, 172.720° E; 1860 m a.s.l.; Dec. 1965; C.L. Batchelor; NZAC 03016359 • 1 nymph; Angelus Peak, Travers Range ; 41.89771° S, 172.74426° E; 1650 m a.s.l.; 7 Jan. 2017; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155139; MPN CW3255 • 2 ♂♂; same data as for preceding; MPN CW3253 , CW3254 • 1 ♀; same data as for preceding; MPN CW3252 • 2 nymphs; same data as for preceding; MPN CW3256 , CW3257 . – Marlborough (MB) • 1 ♂, holotype of Petrotettix nigripes ; Mt Altimarloch, Black Birch Range ; 41.744° S, 173.806° E; 1360 m a.s.l.; 6 Feb. 1970; J.S. Dugdale leg.; NZAC 03016360 , 03015544 • 1 ♀, allotype of Petrotettix nigripes ; same data as for preceding; NZAC 03015510 • 1 ♀; Inkerman Ridge, Crimea Range ; 42.1990° S, 172.8328° E; 2000 m a.s.l.; 24 Jan. 2012; T. Watson leg.; on ridge-top; GenBank: PP155148; MPN CW2643 • 1 ♀; Crimea Creek, Crimea Range ; 42.2001° S, 172.8356° E; 1880 m a.s.l.; 24 Jan. 2012; I. Millar leg.; GenBank: PP155149; MPN CW2647 • 1 ♂; Crimea Creek, Crimea Range ; 42.2020° S, 172.8340° E; 1870 m a.s.l.; 24 Jan. 2012; T. Watson leg.; GenBank: PP155147; MPN CW2676 • 1 nymph; same data as for preceding; GenBank: PP155135; MPN CW2677 • 2 nymphs; same data as for preceding; MPN CW2674 , CW2675 • 1 ♀; Berts Creek ; 42.1180° S, 172.8999° E; 1100 m a.s.l.; 20 Dec. 2011; T. Watson leg.; GenBank: PP155146; MPN CW2648 • 1 ♂; Mt Alexander ; 41.8219° S, 173.6059° E; 1340 m a.s.l.; 27 Apr. 2006; I. Millar leg.; GenBank: PP155134; MPN CW412 • 2 nymphs; Mt Harkness, Black Birch Range ; 41.76021° S, 173.75181° E; 1640 m a.s.l.; 22 Oct. 2016; D. Hegg leg.; on summit rocks; night search + insect net; MPN CW3514 , CW3515 • 1 nymph; Mt Altimarloch, Black Birch Range ; 41.74389° S, 173.80445° E; 1360 m a.s.l.; 23 Oct. 2016; D. Hegg leg.; on rocky outcrop; night search + insect net; GenBank: PP155137; MPN CW3141 • 3 nymphs; same data as for preceding; MPN CW3142 to CW3144 • 1 ♀; same data as for preceding; 6 Jan. 2017; GenBank: PP155140; MPN CW3249 • 2 ♂♂; same data as for preceding; MPN CW3250 , CW3251 • 4 ♂♂; same data as for preceding; 29 Jan. 2018; MPN CW5588 , CW5590 to CW5592 • 3 ♀♀; same data as for preceding; MPN CW5586 , CW5587 , CW5589 • 1 nymph; Mt Richmond, Richmond Range ; 41.47298° S, 173.39135° E; 1600 m a.s.l.; 21 Oct. 2018; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155138; MPN CW4125 • 1 ♂; same data as for preceding; MPN CW5577 • 1 ♀; same data as for preceding; MPN CW5578 • 1 nymph; same data as for preceding; MPN CW4124 • 1 ♂; Slaty Peak, Richmond Range ; 41.48759° S, 173.27426° E; 1520 m a.s.l.; 28 Dec. 2021; D. Hegg leg.; on ridge top; night search + insect net; MPN CW5361 • 1 ♀; same data as for preceding; MPN CW5360 . – Kaikōura (KA) • 1 ♀; Turks Head ; 42.1629° S, 173.2752° E; 1630 m a.s.l.; 18 Jan. 2012; T. Watson leg.; among scree; GenBank: PP155133; MPN CW2649 • 1 ♂; Hodder Huts, Awatere River ; 41.96950° S, 173.63789° E; 1380 m a.s.l.; 4 Apr. 2018; D. Hegg leg.; on rock bluffs; night search + insect net; MPN CW5579 • 1 ♂; Kahutara Saddle ; 42.32217° S, 173.42933° E; 1200m a.s.l.; 1 Apr. 2017; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155136; MPN CW3245 • 5 ♂♂; same data as for preceding; MPN CW3389 , CW3407 to CW3410 • 6 ♀♀; same data as for preceding; MPN CW3388 , CW5555 to CW5559 • 7 nymphs; same data as for preceding; MPN CW3242 to CW3244 , CW3246 to CW3248 , CW3387 .

Description

MEASUREMENTS. See Table 1. Body longer by 1.2 mm (10%) in females ( Table 2).

HEAD. As per generic description. Vertex pale with four thin black lines running perpendicularly to the pronotum, two above the eyes and two near the centre. The lower extremity of the vertex is black, including the fastigium. Frons and labrum mottled grey/ black; clypeus pale. Scapes variegated pale and black. Pedicels and all other segments of the antennae black.

THORAX. In adults, the pronotum, mesonotum and metanotum are either chequered yellow/ black ( Figs 12D , 22C ) or mostly dark ( Fig. 22D–E ). In nymphs, the whole thorax tends to be coloured a dull grey / green ( Fig. 22F ).

LEGS. Longer than in any other species of Isoplectron in both sexes, with pronounced sexual dimorphism. The hind tibiae are on average 10% longer than the body in females, 50% longer than the body in males (max 70%). Fore femora always unarmed at the apex. Mid femora armed with one retrolateral spine at the apex; prolateral apical spine absent. Hind femora armed with up to 12 retrolateral and prolateral ventral linear spines, the retrolateral ones being larger. Fore and mid tibiae armed with one to three pairs of ventral linear spines, with one pair of ventral apical spines, and with one pair of dorsal apical spines. Hind tibiae armed with about 25 dorsal linear spines (min 19, max 37) on both the anterior and the posterior edge ( Fig. 13E ). Hind tibiae armed at the apex with two ventral sub-apical spines, two ventral apical spines, two dorsal apical spines and two dorsal sub-apical spines. The dorsal apical spines are always largest, whereas the ventral sub-apical spines are smallest. First hind tarsal segment armed with up to 18 dorsal linear spines; second hind tarsal segment armed with up to 8 dorsal linear spines.

ABDOMEN. Predominantly dark, almost black, or chequered yellow / black ( Figs 12D , 22C–E ). In nymphs, the whole body tends to be coloured a dull grey /green ( Fig. 22F ).

MALE TERMINALIA. Suranal plate trapezoidal and heavily sclerotised ( Fig. 15A ). Subgenital plate triangular; heavily sclerotised; enlarged and folded upwards like a scoop-shaped trowel at the apex; with a pronounced double keel along its whole length ( Fig. 15B ). Cerci short, on average 13% 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 slender, shorter than subgenital plate. Paraprocts small and covered in dense, stout spinules on the inward-facing side; they are entirely contained within the perimeter of the subgenital plate and are not visible from below ( Figs 7A–C , 15A ). Under the suranal plate there is a retractable cover which presumably protects the genitalia when not in use ( Fig. 20C ; compare with Fig. 15A ).

FEMALE TERMINALIA. Subgenital plate consists of two small, rounded lobes, covered in sparse hair; separated by a gap at least as wide as the lobe themselves ( Figs 7D–F , 18A ). Ovipositor on average two thirds of body length; relatively straight and only lightly recurved upwards near the apex; heavily sclerotised and black in the distal half. Lower valve of ovipositor with 5 to 7 teeth below at the apex. Dorsal surface of upper valve heavily serrated in distal half ( Fig. 18B–C ).

Distribution and habitat

Widespread in the drier alpine regions of New Zealand’s South Island north of the Rangitata River and east of the Main Divide of the Southern Alps. Found almost exclusively on rock well above the tree-line. It feeds on lichen and camouflages well with its background.

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. 7. Isoplectron serratum (Richards, 1972) comb. nov. A–C. Adult ♂, dorsal view of terminalia. A. The Gap, Torlesse Range (MPN CW3182). B–C. Holotype, Mt Binser, Canterbury (CMNZ 000223). B. Original drawing by Richards (1972). C. Photograph of museum specimen, with subgenital plate removed. D–F. Adult ♀, subgenital plate. D. Mt Altimarloch, Black Birch Range (MPN CW5587). E–F. Paratype, Mt St Patrick, St James Range (CMNZ 000223). E. Original drawing by Richards (1972). F. Photograph of museum specimen. Scale bars: 1 mm.

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. 20. Retractable cover in adult male terminalia of cave wētā in the genus Isoplectron Hutton, 1896. A–B. I. pallidum (Richards, 1972) comb. nov. Crown Range Road (MPN CW5560). A. Dorsal view of retractable cover. B. Ventral view of subgenital plate and apex of retractable cover. C. I. serratum (Richards, 1972) comb. nov., dorsal view. Mt Altimarloch, Black Birch Range (MPN CW5588). D. I. maculatum sp. nov., holotype, dorsal view. Middle Mt Peel, South Canterbury (NMNZ AI.071892). Scale bars: 1 mm.

Fig. 22. Live Isoplectron Hutton, 1896 in their natural habitats. A. I. pallidum (Richards, 1972) comb. nov., adult ♀. Staircase Hut Track, Waianakarua. B. I. maculatum sp. nov., adult ♂. Middle Mt Peel, South Canterbury. C–F. I. serratum (Richards, 1972) comb. nov. C. Adult ♀. The Gap, Torlesse Range. D. Adult ♂. Mt Richmond, Richmond Range. E. Mating pair. Mt Altimarloch, Black Birch Range. F. Female nymph. Mt Altimarloch, Black Birch Range.