Isoplectron pallidum, comb. nov.
Creators: name: Hegg, Danilo
name: Morgan-Richards, Mary
name: Trewick, Steven A.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Orthoptera
Rhaphidophoridae
Isoplectron
Isoplectron pallidum

description: Isoplectron pallidum (Richards, 1972) comb. nov.
Figs 1A–B, 3, 6, 8, 10H, 12I, 13D, 14J–L, 17J–L, 20A–B, 22A
Setascutum pallidum Richards, 1972: 165–166, fig. 6.1–6.3.
Setascutum pallidum – Hegg et al. 2022: 4, fig. 1A.
Diagnosis
The smallest species in the genus Isoplectron, I. pallidum has a body length between 8 and 13 mm, the hind tibiae slightly longer than the body in males.
Throughout its distribution range, I. pallidum is sympatric with I. armatum and with Praecantrix silvatica gen. et sp. nov.; indeed, we have found all three species on the same tree trunk. Similar in its look to I. armatum, I. pallidum is most reliably differentiated from the two species listed above by the presence of dorsal linear spines on the first and second hind tarsal segments.
In the Kakanui Mountains and in the St Marys Range in North Otago, I. pallidum is also sympatric with Praecantrix saxicola gen. et sp. nov. In spite of what the name might suggest, the latter species is in fact the one that is reliably identified by its pale colour. The two species also tend to occupy different microhabitats, with I. pallidum most commonly found on rock bluffs, P. saxicola among scree. We have, however, found the two species on the same bluff.
Etymology
‘ Pallĭdus ’ (adj.) is Latin for ‘pale’. Named by Richards (1972) because of the pale coloration of the single specimen she examined. The name is somewhat misleading within this genus.
Material examined (see also Supp. file 1: Table S4 and Fig. S6)
Holotype NEW ZEALAND • ♀, adult; Central Otago (CO), Duffers Saddle, Old Woman Range; 45.1689° S, 169.0757° E; 1250 m a.s.l.; 12 Sep. 1968; J.S. Dugdale leg.; in crevice on rock tor; NZAC 03015582.
Representative male
NEW ZEALAND • ♂, adult; Dunedin (DN), Staircase Hut track, Waianakarua River; 45.28210° S, 170.69724° E; 400 m a.s.l.; 3 Sep. 2016; D. Hegg leg.; on tree trunk; night search; NMNZ AI.071891.
Other material
NEW ZEALAND – Dunedin (DN) • 1 ♀; same data as for representative male; GenBank: PP155125; MPN CW3163 • 1 ♀; Mt Cargill, Dunedin; 45.81242° S, 170.55488° E; 620 m a.s.l.; 22 Nov. 2016; D. Hegg leg.; on rocky outcrop; night search; GenBank: PP155123; MPN CW3448 • 1 ♂; same data as for preceding; MPN CW5605 • 1 ♀; same data as for preceding; MPN CW5604. – Central Otago (CO) • 1 ♂; same data as for holotype; 26 Nov. 2016; D. Hegg leg.; in crevice on rock tor; night search + insect net; GenBank: PP155122; MPN CW3486 • 1 ♂; same data as for holotype; MPN CW3488 • 1 ♀; same data as for preceding; MPN CW3487 • 2 nymphs; same data as for preceding; MPN CW3458, CW3485 • 4 ♂♂; same data as for preceding; 7 May 2017; MPN CW5384 to CW5387 • 3 ♀♀; same data as for preceding; MPN CW3439 to CW3441 • 1 nymph; same data as for preceding; MPN CW3442 • 1 ♂; Nevis Road; 45.16186° S, 169.10122° E; 1120 m a.s.l.; 26 Nov. 2016; D. Hegg leg.; in crevice on rock tor; night search + insect net; MPN CW5383 • 1 ♀; same data as for preceding; MPN CW5382 • 1 nymph; Mt Rosa Track, Queenstown; 45.045° S, 168.963° E; 30 Nov. 2006; L. Cook and P. Johns leg.; in wētā motel; MPN CW703 • 2 nymphs; Nevis Bluff; 45.042° S, 169.012° E; 400 m a.s.l.; Nov. 2009; M. McDonald leg.; MPN CW1040, CW1042 • 1 ♂; Alexandra; 45.256° S, 169.404° E; 250 m a.s.l.; Dec. 2013; T. Jewell leg.; on rock tor; GenBank: PP155121; MPN CW2577 • 1 ♂; same data as for preceding; MPN CW2578 • 1 ♀; same data as for preceding; MPN CW2579 • 1 nymph; Earnscleugh Tailings Reserve, Alexandra; 45.24230° S, 169.36039° E; 130 m a.s.l.; 18 Nov. 2022; D. Hegg leg.; on willow tree next to river; night search + insect net; GenBank: PP155124; MPN CW5553 • 1 ♂; Sutton Salt Lake, Middlemarch; 45.57555° S, 170.08818° E; 250 m a.s.l.; 23 Feb. 2021; D. Hegg leg.; on rock tor; night search + insect net; MPN CW5603 • 1 ♀; same data as for preceding; MPN CW5602 • 2 nymphs; same data as for preceding; MPN CW5209, CW5210 • 1 ♀; Danseys Pass Road; 44.96188° S, 170.32864° E; 650 m a.s.l.; 7 May 2016; D. Hegg leg.; on rock slabs at edge of river; night search + insect net; GenBank: PP155127; MPN CW3014 • 2 nymphs; same data as for preceding; MPN CW3015, CW3016 • 1 ♂; Mt Kyeburn, Danseys Pass; 44.95412° S, 170.31028° E; 1160 m a.s.l.; 16 Jan. 2017; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155128; MPN CW3456 • 2 ♀♀; same data as for preceding; MPN CW4231, CW4245 • 1 ♀; Mt Kyeburn, Danseys Pass; 44.95466° S, 170.31002° E; 1120 m a.s.l.; 16 Apr. 2017; D. Hegg leg.; on rock bluffs; night search + insect net; GenBank: PP155126; MPN CW3455 • 1 ♂, 1 ♀; same data as for preceding; MPN CW4246, CW4247 • 5 ♂♂; Crown Range Road; 44.98128° S, 168.94333° E; 980 m a.s.l.; 14 Nov. 2020; D. Hegg leg.; on rock tor; night search + insect net; MPN CW5560 to CW5563, CW5601 • 1 ♂; Bendigo; 44.96156° S, 169.28727° E; 330 m a.s.l.; 4 Jun. 2023; D. van der Westhuizen leg.; sparse rocks; casual find; MPN CW5637. – Central Otago / Otago Lakes (CO / OL) • 1 ♂; Jollies Hill Pass; 45.57260° S, 168.50332° E; 400 m a.s.l.; 28 Aug. 2020; D. Hegg leg.; on pine tree trunk in highway rest area; casual find; MPN CW5113. – Otago Lakes (OL) • 2 nymphs; Skippers Canyon; 44.892° S, 168.676° E; Nov. 2009; M. McDonald leg.; MPN CW1041, CW1043 • 1 ♂; Mt Iron, Wānaka; 44.69332° S, 169.16855° E; 320 m a.s.l.; 12 Oct. 2018; D. Hegg leg.; on tree trunk; night search + insect net; MPN CW4975 • 1 ♀; same data as for preceding; MPN CW4974.
Description
MEASUREMENTS. See Table 1. No sexual dimorphism in body length.
HEAD. As per generic description. Vertex mottled dark brown with pale patches. Black streaks run from the posterior margin of each eye to the pronotum, resembling the temples in a pair of sun-glasses. Frons pale, with broad, irregular, dark vertical stripes below the scapes of the antennae. Scapes and pedicels of antennae pale mottled cream and brown. All other segments of the antennae are reddish.
THORAX. As per generic description. The pronotum, mesonotum and metanotum are typically coloured brown to dark brown, with elaborate patterns and pale patches on the two posterior segments (Fig. 22A). A pale colour band running through the whole length of the body is also common (Fig. 12I).
LEGS. Fore and mid femora approximately half as long as body. Hind tibiae same length as body in females, on average 15% 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 one to three retrolateral ventral linear spines, and up to three prolateral ventral linear spines. A conspicuous spine on the posterior lower margin of the hind femur is often present, but is never as large as in adult male I. armatum. 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 rarely present. 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 25 dorsal linear spines (min 13, max 34) on both the anterior and the posterior edge (Fig. 13D). 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 eight to twenty dorsal linear spines; second hind tarsal segment armed with three to eleven dorsal linear spines.
ABDOMEN. Typically mottled brown (Fig. 22A). Dark colour morphs with a pale longitudinal band (Fig. 12I) are also commonly encountered.
MALE TERMINALIA. Subgenital plate triangular, very narrow at apex, lacking a keel but with a visible median suture (Fig. 14K). Cerci on average 20% of body length, covered in long hairs; tapering gradually along their whole length and ending with a blunt tip at the apex. Styli slender and tapering, generally shorter than subgenital plate. Paraprocts form a horseshoe covered in dense, stout spinules; two triangular lobes rising vertically at the base of the paraprocts are also covered in spinules (Fig. 14J, L). Under the suranal plate there is a retractable cover which presumably protects the genitalia when not in use (Fig. 20A–B; compare with Fig. 14J).
FEMALE TERMINALIA. Subgenital plate consists of two small lobes at an angle, touching at the vertex (Figs 6, 17J). Ovipositor on average 80% of body length, relatively straight in the basal half, tapering and moderately recurved upwards only near the apex. Lower valve of ovipositor with 5 to 7 teeth below at the apex. Dorsal surface of upper valve more heavily serrated in distal half than in I. armatum (Fig. 17K–L).
Distribution and habitat
Isopletron pallidum is only known from the Otago Region in New Zealand’s South Island, between the east coast and Lakes Wānaka and Wakatipu, at elevations ranging from 250 m to 1250 m a.s.l. It occupies a range of habitats including montane forests, rock tors and bluffs. Populations may be locally dense, with several specimens hiding in cracks in the rock or under bark on tree trunks.
description: Published as part of 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, pp. 1-75 in European Journal of Taxonomy 971 on pages 39-41, DOI: 10.5852/ejt.2024.971.2761, http://zenodo.org/record/14451786