Isoplectron ferratum sp. nov.

urn:lsid:zoobank.org:act: 81140EE2-3572-4274-869C-A617DBF74D68

Figs 3, 8, 10C, 12F, 13H, 15J–L, 18J–L, 23B

Diagnosis

A small insect (body length 9 to 13 mm), most commonly of uniform rusty colour (Figs 12F, 23B). Longitudinally striped morphs are encountered on occasion and could be mistaken for I. virgatum sp. nov. Striped morphs of I. ferratum sp. nov. have fewer, broader stripes than I. virgatum and are darker overall. Isoplectron virgatum also occupies a different micro-habitat and generally lacks the retro-lateral spine at the apex of the mid femur.

Isoplectron ferratum sp. nov. could be mistaken for I. armatum . The two species are allopatric but have adjacent ranges. Isoplectrum ferratum has shorter legs than I. armatum, has lighter colour with rusty/ red tones and lacks the prominent ventral spine on the posterior edge of the hind femur.

Isoplectron ferratum sp. nov. is sympatric with I. bicolor sp. nov. throughout its distribution range and could be mistaken for a nymph of the latter species. The state of development of terminalia or ovipositor will show whether a specimen is an adult of the smaller I. ferratum or a nymph of the larger I. bicolor .

On Taranaki, I. ferratum sp. nov. could be confused with several species in the genus Neonetus . While insects in the latter genus generally have prolateral and retrolateral spines at the apex of fore and mid femora, an examination of the male terminalia or of the female posterior sternites is advised for a correct identification of these smaller species of cave wētā.

Etymology

‘ Ferrum ’ is the Latin word for ‘horseshoe’ (among other meanings). ‘ Ferrātus ’ (adj.) means ‘fitted with a horseshoe’, after the shape of the female subgenital plate (see Fig. 18J).

Material examined (see also Supp. file 1: Table S8)

Holotype NEW ZEALAND • ♂, adult; Nelson (NN), Cave Brook, Gouland Downs; 40.89153° S, 172.35449° E; 630 m a.s.l.; 4 Feb. 2018; D. Hegg leg.; in beech tree canopy; night search + insect net; NMNZ AI.071896.

Paratype NEW ZEALAND • 1 ♀, adult; Marlborough Sounds (SD), Mt Stokes; 41.08747° S, 174.10983° E; 1000 m a.s.l.; 17 Nov. 2018; D. Hegg leg.; on beech tree; night search + insect net; GenBank: PP155117; NMNZ AI.071897 .

Other material

NEW ZEALAND – Buller (BR) • 1 nymph; Nina Valley; 42.45974° S, 172.36472° E; 650 m a.s.l.; 26 Jan. 2018; D. Hegg leg.; on large rock in forest; night search + insect net; GenBank: PP155112; MPN CW3778 • 1 nymph; same data as for preceding; GenBank: PP155113; MPN CW3779 • 2 ♂♂; same data as for preceding; MPN CW5607, CW5608 • 1 ♀; same data as for preceding; MPN CW5609. – Nelson (NN) • 1 ♀; Blue Creek, Mt Owen; 41.51561° S, 172.56022° E; 1100 m a.s.l.; 11 Jan. 2019; D. Hegg leg.; on tree trunk; night search + insect net; GenBank: PP155114; MPN CW5610 • 1 ♀; Graham River North Branch; 41.19414° S, 172.80776° E; 170 m a.s.l.; 19 Dec. 2011; S. Trewick leg.; MPN CW1800 • 1 ♂; Mt Arthur Track, Mt Arthur; 41.19966° S, 172.72180° E; 1180 m a.s.l.; 21 Dec. 2020; D. Hegg leg.; on tree trunk; night search + insect net; MPN CW5575 • 1 ♂; Salisbury Lodge, Mt Arthur; 41.18465° S, 172.64217° E; 1200 m a.s.l.; 24 Dec. 2020; D. Hegg leg.; on tree trunk; night search + insect net; MPN CW5576 • 2 ♂♂; Chaffey Hut, Cobb River; 41.09531° S, 172.57310° E; 900 m a.s.l.; 26 Dec. 2020; D. Hegg leg.; on tree trunk; night search + insect net; MPN CW5573, CW5574 • 3 ♀♀; same data as for preceding; MPN CW5570 to CW5572 • 1 ♂; Gouland Downs Hut, Heaphy Track; 40.89060° S, 172.35334° E; 630 m a.s.l.; 16 Sep. 2005; M. Ogle leg.; between sheets of plywood; casual find; MPN CW343 • 1 ♀; same data as for preceding; MPN CW342 • 1 ♀; same data as for holotype; 26 Dec. 2016; GenBank: PP155116; MPN CW4036 • 1 ♂, 1 ♀; same data as for holotype; MPN CW3774, CW4953 • 2 ♂♂; Awaroa, Abel Tasman NP; 40.863° S, 173.043° E; 10 m a.s.l.; Jan. 2011; M. Morgan-Richards and S. Trewick leg.; MPN CW1953, CW1954 • 1 ♀; same data as for preceding; 18 Jan. 2017; S. Trewick leg.; in sink outside hut; casual find; GenBank: PP155110; MPN CW3229 • 1 ♂; Pakawau Bush Rd, Collingwood; 40.583° S, 172.657° E; 20 m a.s.l.; 27 Jan. 2010; M. Morgan-Richards and S. Trewick leg.; MPN CW1907 • 1 ♀; same data as for preceding; MPN CW1906 • 1 nymph; Farewell Spit; 40.51417° S, 172.75389° E; 10 m a.s.l.; 5 Feb. 2018; D. Hegg leg.; on tree trunk; night search + insect net; GenBank: PP155111; MPN CW3768 • 1 ♂; same data as for preceding; MPN CW5599 • 1 ♀; same data as for preceding; MPN CW5600 • 1 ♀; Cape Farewell; 40.50490° S, 172.70925° E; 100 m a.s.l.; 1 Dec. 2019; E. Trewick leg.; under rimu bark; GenBank: PP155115; MPN CW4627. – Taranaki (TK) • 1 ♂; Dawson Falls, Taranaki Mounga; 39.330° S, 174.110° E; 800 m a.s.l.; 1 Jun. 2008; M. Morgan-Richards and S. Trewick leg.; GenBank: PP155109; MPN CW817 .

Description

MEASUREMENTS. See Table 1. Body length approximately 11 mm in both males and females; no sexual dimorphism in body or leg length.

HEAD. Vertex variegated with a complex pattern of pale patches and thin dark stripes. 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 dark patches under the scapes of the antennae, two dark patches under the eyes and another two smaller dark patches near the median line on each of frons and clypeus. Scapes of antennae pale, criss-crossed by a pattern of thin, dark stripes; pedicels pale; all other segments of the antennae reddish-brown.

THORAX. Most commonly rusty red / brown (Fig. 12F).

LEGS. Relatively short, without sexual dimorphism. The hind tibiae are on average 90% of body length in both males and females. 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 four 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 on rare occasion. 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 14 dorsal linear spines (min 11, max 16) on both the anterior and the posterior edge (Fig. 13H). 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 usually rusty red / brown throughout (Figs 12F, 23B). Specimens we have examined from Mt Stokes and Farewell Spit have a pale diamond or a longitudinal band on the back, bordering two dark brown bands either side. In females only, the seventh sternite is equipped with two ventral protuberances; the eighth sternite with three ventral protuberances (Fig. 18J).

MALE TERMINALIA. Suranal plate trapezoidal with conspicuous hair tufts on the two posterior corners; the posterior margin has a deep, narrow indentation in the middle (Fig. 15J). Subgenital plate pear-shaped; covered in very sparse, thin tomentum except near the base on the sides, which are glabrous; with a thin keel along its whole length (Fig. 15K). Cerci on average 20% of body length, covered in sparse, mostly short hairs; tapering gradually along their whole length and ending with a blunt tip at the apex. Styli short and stumpy, not reaching to the apex of the subgenital plate. Paraprocts narrow, tapering right from the base to a blunt tip at the apex; glabrous (Fig. 15J).

FEMALE TERMINALIA. Subgenital plate consists of two elongated, rounded lobes in the shape of a horseshoe (Fig. 18J). Ovipositor on average 70% of body length; moderately recurved upwards from the base to the apex; lower valve with 6 to 9 teeth below at the apex; dorsal surface of upper valve serrated in distal third (Fig. 18K–L).

Distribution and habitat

An arboreal insect confined to the regions in the north-west of South Island from Lewis Pass to Farewell Spit and to the Marlborough Sounds, and to Taranaki Mounga in North Island (Fig. 10C).