Isoplectron bicolor, 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 : 35-39

Isoplectron bicolor sp. nov.

urn:lsid:zoobank.org:act:EBEFE4F1-4F9B-4173-AF54-A53151132217

Figs 3 , 8 , 10E , 12C , 13C , 14G–I , 17G–I , 21E–F

Diagnosis

The largest species in the genus Isoplectron ; in the adult form, it is unmistakeable due to its characteristic coloration, with tawny head, thorax, fore and mid legs and hind femora, which contrast with the near black abdomen and hind tibiae ( Fig. 21E ). Nymphs could be easily mistaken for those of I. ferratum sp. nov., with which it is sympatric, and with I. armatum . The latter species however is not found within the distribution range of I. bicolor sp. nov.

Etymology

‘ Bĭcŏlor ’ (adj.) is Latin for ‘two-coloured’ – because of the unique contrasting coloration, tawny in the front and black in the back.

Material examined (see also Supp. file 1: Table S3)

Holotype NEW ZEALAND • ♂, adult; Nelson (NN), Cave Brook, Gouland Downs ; 40.89153° S, 172.35449° E; 620 m a.s.l.; 4 Feb. 2018; D. Hegg leg.; on tree trunk; night search + insect net; NMNZ AI.071889 .

Paratype NEW ZEALAND • 1 ♀, adult; Nelson (NN), Chaffey Hut, Cobb River ; 41.09600° S, 172.57535° E; 880 m a.s.l.; 26 Dec. 2020; D. Hegg leg.; on tree trunk; night search + insect net; NMNZ AI.071890 .

Other material

NEW ZEALAND – Buller (BR) • 1 ♀; Nina Hut, Nina Valley ; 42.46573° S, 172.32202° E; 760 m a.s.l.; 15 Mar 2015; in sink outside hut; photograph only; iNaturalist 1909084. – Nelson (NN) • 1 nymph; same data as for holotype; 20 Apr. 2016; GenBank: PP155151 ; MPN CW2991 • 1 ♂; same data as for holotype; GenBank: PP155152 ; MPN CW3758 • 1 ♂; Mt Arthur Tablelands ; 41.18500° S, 172.64370° E; 1180 m a.s.l.; 8 Feb. 2018; D. Hegg leg.; in beech tree canopy; night search + insect net; GenBank: PP155153 ; MPN CW3760 • 1 ♂; same data as for preceding; 24 Dec. 2020; MPN CW5346 • 3 nymphs; same data as for paratype; MPN CW5195 , CW5197 , CW5198 • 1 ♂; same data as for paratype; 5 Jan. 2022; MPN CW5357 .

Description

MEASUREMENTS. See Table 1 . The only female collected has a body longer than any of the examined males by two to six millimetres.

HEAD. As per generic description. Vertex tawny with dark streaks. A dark patch extends behind the posterior margin of the eye. Frons pale, with dark vertical stripes below the scapes of the antennae. Scapes of antennae tawny. All other segments of the antennae are reddish.

THORAX. Pronotum, mesonotum and metanotum tawny with complex dark pattern ( Fig. 12C ).

LEGS. All leg segments are tawny, except for the hind tibiae, which are near black in adults. Hind tibiae of same length as body in females, up to 50% longer than body in males. 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 nine to seventeen prolateral ventral linear spines, very small, and four to eight strong retrolateral ventral linear spines. Fore tibiae armed with two pairs of ventral linear spines, and with one pair of ventral apical spines. 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 12 to 16 dorsal linear spines on both the anterior and the posterior edge ( Fig. 13C ). 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 occasionally armed with a few dorsal linear spines. Second tarsal segment unarmed except at the apex.

ABDOMEN. Typically dark, near black in adults, although a tawny diamond may extend from the thorax into the first few tergites ( Figs 12C , 21E ). Nymphs often have a diamond pattern on the back ( Fig. 21F ).

MALE TERMINALIA. Subgenital plate with central lobe at least twice as long as lateral lobes, glabrous, with visible keel at centre ( Fig. 14H ). Cerci with alternating tawny and dark bands; on average one quarter of body length; covered in long hairs; tapering gradually along their whole length and ending with a blunt tip at the apex. Styli slender, covered in sparse setae, extending beyond the apex of the subgenital plate. Paraprocts with pronounced lateral lobes at the apex, which is covered in dense, stout spinules ( Fig. 14G ). The paraprocts project beyond the apex of the subgenital plate and are therefore visible from below ( Fig. 14H ).

FEMALE TERMINALIA. Subgenital plate consists of two large, elongated lobes, flat at the vertex, which is covered in short hair ( Fig. 17G ). Ovipositor three quarters of body length, tapering and curving upwards gradually along its whole length. Lower valve of ovipositor with 6 teeth below at the apex. Dorsal surface of upper valve finely serrated in distal half ( Fig. 17H–I ).

Distribution and habitat

A cryptic, arboreal insect, confined to the north-west regions of New Zealand’s South Island between Lewis Pass and Kahurangi National Park ( Fig. 10E ). It is believed to live primarily in the tree canopy in native forests.

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. 14. 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. armatum armatum Hutton, 1896. A–B. Kaiterau Trail, Kaikōura (MPN CW4938). C. Pioneer Park, Ōpihi River (MPN CW5554). D–F. I. armatum aciculatum Karny, 1937. Ohakune. D. MPN CW5647. E–F. MPN CW5646. G–I. I. bicolor sp. nov., Cave Brook, Gouland Downs. G–H. Holotype (NMNZ AI.071889). I. MPN CW3758. J–L. I. pallidum (Richards, 1972) comb. nov. J, L. Staircase Hut track, Waianakarua River (NMNZ AI.071891). K. Mt Kyeburn, Danseys Pass (MPN CW3455). Scale bars: 1 mm.

Fig. 17. Adult female terminalia of cave wētā in the genus Isoplectron Hutton, 1896. Left column: subgenital plate; central and right columns: ovipositor. A–C. Isoplectron armatum armatum Hutton, 1896. South Mavora Lake (MPN CW4927). D–F. I. armatum aciculatum Karny, 1937. Ohakune. D. MPN CW5648. E–F. MPN CW5650. G– I. I. bicolor sp. nov., paratype (NMNZ AI.071890). Chaffey Hut, Cobb River. J–L. I. pallidum (Richards, 1972) comb. nov. Duffers Saddle, Old Woman Range (MPN CW5387). Scale bars: 1 mm.

Fig. 21. Live Isoplectron Hutton, 1896 in their natural habitats. A–C. I. armatum armatum Hutton, 1896. A. Adult ♂ showing the most common habitus, dark brown back with two pale patches on the metanotum. Raincliff Reserve, Ōpihi River, South Canterbury. B. Adult ♂ with diamond-shaped dorsal pattern. Hinau Track, Kaikōura. C. Adult ♀ with broad longitudinal dorsal band. Pioneer Park, Ōpihi River, South Canterbury. D. I. armatum aciculatum Karny, 1937, adult ♀. Ohakune. E–F. I. bicolor sp. nov. E. Adult ♂. Mt Arthur Tablelands, Kahurangi NP. F. Male nymph. Chaffey Hut, Cobb River.