Praecantrix saxicola, 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 : 61-63

Praecantrix saxicola gen. et sp. nov.

urn:lsid:zoobank.org:act:7888A528-5ABC-4CBA-AA33-4641DAA7CB26

Figs 3 , 9 , 10J , 12L , 13K , 16J–L , 19J–L , 23D

Diagnosis

The largest of the two species in the genus Praecantrix gen. nov. (body length 9 to 14 mm), it is characterised by sexual dimorphism, the females being larger than males, a pale grey colour throughout and a dense tomentum covering the whole insect. This is in contrast to Praecantrix silvatica gen. et sp. nov., which is glabrous and shiny, and has a clear, crisp line delimiting the white body under-parts from the dark dorsal regions.

In the western part of its distribution range, P. saxicola gen. et sp. nov. is sympatric with species of Pharmacus and with Notoplectron brewsterense . It is most easily differentiated from Pharmacus by its lighter coloration, smaller size and micro-habitat preferences, with Pharmacus being more often found in cracks in solid rock. Notoplectron brewsterense is stockier, with shorter legs, has articulated linear spines on the hind tibiae and is glabrous, whereas P. saxicola is covered in fine tomentum. Additionally, female Pharmacus and Notoplectron have a smooth upper valve of the ovipositor, whereas P. saxicola has an ovipositor serrated above in the distal third ( Fig. 19K–L ).

In Otago, P. saxicola gen. et sp. nov. is sympatric with Isoplectron pallidum . The latter species, however, prefers cracks or small pockets in solid rock, and (in spite of the name) has a darker body colour.

Etymology

The Latin noun ‘ saxum ’ means ‘stone’, ‘rock’; in the plural also ‘stony place’. The insect is a dweller of stony places.

Material examined (see also Supp. file 1: Table S12)

Holotype

NEW ZEALAND • ♂, adult; Mackenzie (MK), Mt Wakefield , Aoraki / Mt Cook NP; 43.71987° S, 170.12763° E; 1450 m a.s.l.; 13 May 2017; D. Hegg leg.; broken rocks on ridgeline; night search + insect net; NMNZ AI.071904.

Paratype

NEW ZEALAND • 1 ♀, adult; Central Otago (CO), Mt St. Bathans ; 44.71826° S, 169.77104° E; 1650 m a.s.l.; 9 Mar. 2019; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155085; NMNZ AI.071905 .

Other material

NEW ZEALAND – Central Otago (CO) • 1 ♂, 1 ♀; Mt Kyeburn, Danseys Pass ; 44.95471° S, 170.30851° E; 1100 m a.s.l.; Dec. 2013; T. Jewell leg.; in scree among bluffs; GenBank: PP155088, PP155089; MPN CW2574 , CW2575 • 3 ♂♂; same data as for preceding; MPN CW2572 , CW2573 , CW2576 • 1 ♀; same data as for preceding; 16 Jan. 2017; D. Hegg leg.; night search + insect net; GenBank: PP155087; MPN CW3520 • 1 ♀; Awakino Ski-field, St Marys Range ; 44.78° S, 170.31° E; 1800 m a.s.l.; 20 Apr. 1998; B. Sinclair leg.; in scree; MPN CW173 • 1 ♂; same data as for paratype; GenBank: PP155086; MPN CW4317 • 2 ♀♀; same data as for paratype; MPN CW4551 , CW4552 • 3 nymphs; same data as for paratype; MPN CW4318 to CW4320 . – Mackenzie (MK) • 1 ♂; Ahuriri River East Branch; 44.27917° S, 169.74279° E; 1720 m a.s.l.; 30 Apr. 2022; D. Hegg leg.; in scree among bluffs; night search + insect net; MPN CW5611 • 1 ♀; same data as for preceding; MPN CW5612 • 1 ♀; Mt Wakefield, Aoraki / Mt Cook NP; 43.70548° S, 170.12192° E; 1680 m a.s.l.; 12 Mar. 2016; D. Hegg leg.; on sparsely vegetated ground; night search; GenBank: PP155084; MPN CW2880 • 1 ♂; Mt Wakefield, Aoraki / Mt Cook NP; 43.71063° S, 170.12445° E; 1750 m a.s.l.; 18 Mar. 2017; D. Hegg leg.; broken rocks on ridgeline; night search + insect net; MPN CW3540 • 1 nymph; same data as for preceding; MPN CW3332 • 1 ♀; same data as for preceding; 17 Apr. 2017; MPN CW3946 • 1 nymph; same data as for preceding; MPN CW3947 • 1 ♀; Mt Wakefield, Aoraki / Mt Cook NP; 43.71798° S, 170.12875° E; 1540 m a.s.l.; 13 May 2017; D. Hegg leg.; broken rocks on ridgeline; night search + insect net; MPN CW3517 . – South Canterbury (SC) • 1 ♂; Fox Peak ; 43.84° S, 170.79 °E; 2000 m a.s.l.; 22 Feb. 2015; S. Trewick leg.; GenBank: PP155082; MPN CW2811 • 1 ♀; same data as for preceding; GenBank: PP155083; MPN CW2812 .

Description

MEASUREMENTS. See Table 1. Sexual dimorphism in body length, with females being nearly 25% larger than males.

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. Grey patches behind the eyes. Eyes grey-green. Frons, clypeus and labrum pale, with two faint dark patches below the scapes of the antennae. Labial and maxillary palps pale. Scapes and pedicels pale; flagellum reddish-brown.

THORAX. Pronotum, mesonotum and metanotum grey with a pale median line, covered in fine tomentum ( Fig. 12L ).

LEGS. Sexual dimorphism present. The hind tibiae are about the same length as the body in females, 10% longer than the body in males. Since females are larger than males by approx. 25%, females have longer legs. 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 one prolateral and one to three retrolateral ventral linear spines, the retrolateral ones being larger. Fore and mid tibiae armed with two pairs of ventral linear spines, one pair of ventral apical spines and one pair of dorsal apical spines. Hind tibiae armed with about 26 dorsal linear spines (min 22, max 33) on both the anterior and the posterior edge. 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 largest. First hind tarsal segment armed with two to seven dorsal linear spines; second hind tarsal segment occasionally armed with one dorsal linear spine.

ABDOMEN. All tergites covered in fine tomentum; grey with a pale median line running along the whole length of the body ( Fig. 12L ). Sternites pale.

MALE TERMINALIA. Same as in Praecantrix silvatica gen. et sp. nov., but with longer bristles on the two lobes at the apex of the subgenital plate ( Fig. 16J–L ). Cerci on average 15% of body length, covered in sparse, mostly short hair; conical in the basal half, tapering to a blunt tip in the distal half. Styli short and stumpy.

FEMALE TERMINALIA. Subgenital plate square, with two rounded lobes on the distal corners, not as pronounced as in Praecantrix silvatica gen. et sp. nov., covered with sparse hair at the apex ( Fig. 19J ). Ovipositor approximately 70% of body length; nearly straight and only weakly recurved upwards near the apex; lower valve with 5 to 7 teeth below at the apex; dorsal surface of upper valve finely serrated in distal third ( Fig. 19K–L ).

Distribution and habitat

A small alpine rhaphidophorid that inhabits the dry alpine regions east of the Southern Alps, in Central Otago and in the Mackenzie Country ( Fig. 10J ). It is predominantly found on scree slopes or boulder fields and is most easily recognised by the light grey or grey-brown body colour and grey-green eye colour. When disturbed, it jumps erratically up and down until it falls into a hole between rocks.

Unresolved taxa

We have one specimen ( Fig. 8 ) from old-growth forest in Ohakune (Taupō Region, North Island), which we have been unable to resolve (specimen code MPN CW5373; GenBank: PP155150; iNaturalist 73080453). This is a male nymph belonging to a taxon that appears to be sister to Isoplectron bicolor sp. nov. based on DNA analysis and on the numerous ventral linear spines on the hind femora. We have spent in excess of 20 nights searching for more specimens, in all four seasons, without any luck. Most likely, we are dealing with a cryptic tree canopy species, like I. bicolor . The latter is the taxon for which we have obtained the smallest sample size in this study; the one adult female we have been able to collect also took in excess of ten person nights searching.

It is likely that a dedicated tree canopy sampling approach will be required to capture this elusive insect. Methods that have been employed in similar forest habitats include fogging and branch clipping ( Ozanne 2005), even tree felling ( Otte & Alexander 1983: 397). We do not favour any of these methods since they are destructive and they are better suited to generic biodiversity monitoring than to targeting a specific insect, especially one that cannot even be located by sound. More realistic approaches may be liaising with road maintenance crews, who occasionally need to fell trees close to the road verge, or building a structure to access the canopy, e.g. a crane or a suspended walkway ( Ozanne 2005).

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. 9. Gene tree for the two morphologically identified species of Praecantrix gen. nov. using Maximum Likelihood analysis of ~850 bp of mtDNA (COI) from 22 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. 16. Adult male terminalia of cave wētā in the genera Isoplectron Hutton, 1896 and Praecantrix gen. nov. Left column: dorsal view; central column: ventral view (subgenital plate); right column: lateral view. A–C. Isoplectron parallelum sp. nov., holotype. Ahumairangi Town Belt, Wellington (NMNZ AI.071898). D–F. Praecantrix silvatica silvatica gen., sp. et subsp. nov. D, F. Holotype. Mt Arthur Tablelands, Kahurangi NP (NMNZ AI.071900). E. Richmond Saddle, Marlborough (MPN CW4136). G–I. Praecantrix silvatica lutea gen., sp. et subsp. nov., holotype. McLean Falls, Catlins Forest (NMNZ AI.071902). J–L. Praecantrix saxicola gen. et sp. nov., holotype. Mt Wakefield, Aoraki / Mt Cook NP (NMNZ AI.071904). Scale bars: 1 mm.

Fig. 19. Adult female terminalia of cave wētā in the genera Isoplectron Hutton, 1896 and Praecantrix gen.nov.Leftcolumn:subgenitalplate; centraland right columns:ovipositor.A–C. Isoplectronparallelum sp. nov., paratype. Ahumairangi Town Belt, Wellington (NMNZ AI.071899). D–F. Praecantrix silvatica silvatica gen., sp. et subsp. nov. D. Paratype. Smoothwater Bay, South Westland (NMNZ AI.071901). E–F. Aspiring Hut, Mt Aspiring NP (MPN CW3518). G–I. Praecantrix silvatica lutea gen., sp. et subsp. nov. G. Paratype. Ōpoho, Dunedin (NMNZ AI.071903). H–I. McLean Falls, Catlins (MPN CW4946). J–L. Praecantrix saxicola gen.et sp. nov., paratype. Mt St Bathans, Central Otago (NMNZ AI.071905). 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.

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.