Trigonidium (Trigonidium) maoricum ( Walker, 1869 )

Hegg, Danilo, 2024, Small crickets of New Zealand (Orthoptera: Grylloidea: Trigonidiidae and Mogoplistidae), with the description of two new genera and species, European Journal of Taxonomy 955 (1), pp. 1-87 : 58-64

Trigonidium (Trigonidium) maoricum ( Walker, 1869)

Figs 29–31 , 32A–D , 38A

Scleropterus maoricus Walker, 1869: 74–75 .

Scleropterus maoricus – Hutton 1881: 79.

Trigonidium maoricum – Kirby 1906: 78. — Caudell 1927: 22.

Metioche maorica – Chopard 1968: 334–335.

Diagnosis

A small trig (body length 4.5 to 6 mm), with black body and yellow legs. Two morphs in adult insect, without hindwings or auditory tympana, or with hindwings and auditory tympana, as per generic diagnosis.

Etymology

The Latin adjective maoricus refers to the native inhabitants of New Zealand.

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

Note: Walker’s original type series includes three syntypes. Here, I designate one of these as lectotype, the remaining two as paralectotypes.

Lectotype

NEW ZEALAND • ♂, adult; NHMUK 014666694 .

Paralectotypes

NEW ZEALAND • 2 ♀♀; NHMUK 014666695 , 014666696 .

Other material

NEW ZEALAND – Otago Lakes (OL) • 1 ♂; Glendhu Bay, Lake Wānaka ; 44.67430° S, 169.01891° E; 300 m a.s.l.; 11 Apr. 2021; M. Bowie leg.; photograph only; iNaturalist 73602690 . – South Canterbury (SC) • 1 ♀; Makikihi ; 44.62642° S, 171.15641° E; 10 m a.s.l.; 17 Feb. 2024; S. Saito leg.; photograph only; iNaturalist 199549116 . – Mid Canterbury (MC) • 4 ♀♀; Māhoe Reserve, Lincoln ; 43.63415° S, 172.48679° E; 20 m a.s.l.; 25 Oct. 2021; D. Hegg leg.; grassland; insect net; MPN OR0274 to OR0277 • 1 ♂, 1 ♀; Tumbledown Bay, Banks Peninsula ; 43.85050° S, 172.77288° E; 10 m a.s.l.; 12 Aug. 2023; D. Hegg leg.; grassland; insect net; MPN OR0267 , OR0268 • 2 ♂♂; same data as for preceding; 15 Dec. 2023; MPN OR0269 , OR0271 • 1 ♂; same data as for preceding; GenBank: PP761111 ; MPN OR0270 • 2 ♂♂; same data as for preceding; 14 Jan. 2024; MPN OR0272 , OR0273 . – Kaikōura (KA) • 1 ♀; Oaro ; 42.51485° S, 173.50538° E; 40 m a.s.l.; 26 Feb. 2024; J. Stokes leg.; built area; photograph only; iNaturalist 200904066 . – Marlborough Sounds (SD) • 1 ♀; Picton ; 41.28492° S, 174.01132° E; 20 m a.s.l.; 11 Dec. 2018; D. Hegg leg.; on flowering shrubs; photograph only; iNaturalist 33506134. – Wellington (WN) • 1 adult; Johnsonville, Wellington ; 41.21371° S, 174.80224° E; 200 m a.s.l.; 10 Apr. 2022; B. Wright leg.; built area; photograph only; iNaturalist 111076401 . – Wairarapa (WA) • 1 ♀; Riversdale Beach ; 41.08263° S, 176.06787° E; 20 m a.s.l.; 5 Mar. 2022; L. Bennett; built area; photograph only; iNaturalist 108557205 . – Wanganui (WI) • 1 ♀; Palmerston North ; 40.35795° S, 175.62735° E; 60 m a.s.l.; 26 Mar. 2022; J. Charles leg.; built area; photograph only; iNaturalist 109511014 • 1 ♀; Ashhurst ; 40.28196° S, 175.74777° E; 100 m a.s.l.; 15 Mar. 2019; G. Smith leg.; built area; photograph only; iNaturalist 21238691. – Hawke’s Bay (HB) • 1 ♂, 3 ♀♀; Waimārama Domain ; 39.81606° S, 176.99426° E; 10 m a.s.l.; 15 Mar. 2024; D. Hegg leg.; grassland; insect net; MPN OR0328 to OR0331 • 1 ♀; same data as for preceding; GenBank: PP761110 ; MPN OR0327 • 1 ♀; Te Wainohu Beach , Waimārama; 39.84155° S, 176.99671° E; 10 m a.s.l.; 16 Mar. 2024; D. Hegg leg.; grassland; insect net; GenBank: PP761113 ; MPN OR0332 . – Taranaki (TK) • 1 ♀; Awakino Gorge ; 38.62087° S, 174.74416° E; 130 m a.s.l.; 19 Mar. 2024; D. Hegg leg.; uncultivated grass; insect net; MPN OR0326 . – Taupō (TO) • 1 adult; Pukawa Bay, Lake Taupō ; 38.937° S, 175.750° E; 460 m a.s.l.; 24 Mar. 2019; D. Clarke; photograph only; iNaturalist 21549888. – Bay of Plenty (BP) • 1 ♂; Springfield, Rotorua ; 38.15950° S, 176.23428° E; 300 m a.s.l.; 7 Mar. 2022; A. MacArthur leg.; built area; photograph only; iNaturalist 108097615 • 1 ♀; Ōhope, Whakatane ; 37.97699° S, 177.07931° E; 10 m a.s.l.; 18 Feb. 2021; K. Steeds leg.; photograph only; iNaturalist 69740141. – Waikato (WO) • 1 ♀; Top10 Holiday Park , Cambridge; 37.90602° S, 175.47978° E; 60 m a.s.l.; 24 Mar. 2024; D. Hegg leg.; built area; jar; GenBank: PP761114 ; MPN OR0342 . – Coromandel (CL) • 2 ♂♂, 1 ♀; Coromandel ; 36.76220° S, 175.49157° E; 5 m a.s.l.; 6 Apr. 2024; D. Hegg leg.; grassland; insect net; MPN OR0394 to OR0396 • 1 ♂; Whitianga ; 36.81413° S, 175.69529° E; 10 m a.s.l.; 30 Jan. 2024; C. McCollum leg.; built area; jar; NZAC 03037192 . – Auckland (AK) • 1 ♂; Point England, Auckland ; 36.88352° S, 174.85972° E; 10 m a.s.l.; 27 Feb. 2024; C. Winks leg.; in lighted porch at night; MPN OR0309 . – Northland (ND) • 4 ♂♂, 5 ♀♀; Kerikeri ; 35.24029° S, 173.93822° E; 100 m a.s.l.; 22 Mar. 2022; D. Hegg leg.; grassland; insect net; MPN OR0278 to OR0286 • 3 ♂♂, 2 ♀♀, adult; same data as for preceding; NZAC 03037187 to NZAC 03037191 • 3 ♂♂; Coopers Beach ; 34.99248° S, 173.50334° E; 20 m a.s.l.; 30 Mar. 2024; D. Hegg leg.; grassland; insect net; MPN OR0372 to OR0374 • 1 ♂; same data as for preceding; GenBank: PP761112 ; MPN OR0371 • 1 ♂; Te Paki ; 34.50872° S, 172.82424° E; 90 m a.s.l.; 29 Mar. 2024; D. Hegg leg.; grassland; insect net; MPN OR0370 .

Emended description

The species is redescribed here, since Walker’s original description (1869) is extremely scant and is for the female only.

MEASUREMENTS. See Table 7 . Females are slightly larger than males.

HEAD ( Fig. 29A–B ). Shaped like an inverted triangle, widest at compound eyes, about as high as wide in frontal view. Compound eyes large and bulging, separated by a gap approximately equal to one eye length. Ocelli inconspicuous. Head colour black throughout, except for brown patches under scapes of antennae and on rostrum. However, it should be noted that the head colour in trigs may vary over time in an adult, darkening as the insect ages ( Rentz & Su 2019: 285, 317). Vertex with short, sparse hairs and three pairs of long, stout bristles either side of median suture. Frons glabrous. Antennae: scapes and pedicels black, flagelli yellow. Maxillary palps black, except for penultimate segment, which is brown. Terminal segment of maxillary palps shaped like a flattened cone, covered in dense, short hairs.

THORAX. Pronotum black, woolly in its look due to being covered in white hairs.

WINGS ( Fig. 29C ). Forewings mainly with longitudinal veins in both males and females, but with a stridulum approx. 200 µm long and with 28 to 40 teeth in males ( Fig. 29E ). In wingless morph, hindwings absent; tegmina thin, transparent and appressed to abdomen. In winged morph, hindwings present; tegmina thick and coloured yellow-brown.

LEGS. Fore and middle legs uniform yellow-red; posterior legs variegated, with yellow-red background and a complex brown pattern. All legs covered in dense, short hairs throughout. Tibia I with a long ventral spur at apex. In winged morph only, auditory tympana present on both anterior and posterior sides of Tibia I; anterior tympanal opening 30% longer than posterior tympanum ( Fig. 29F–G ). Tibia II bearing two ventral spurs at apex, subequal in length. Tibia III armed with three pairs of subapical spurs dorsally, alternated. All apical and subapical spurs pale in proximal half, brown in distal half; covered in dense hairs. Tibia III inner ventral apical spur absent, like in all Trigonidiinae . Length of outer apical spur on Tarsomere III-1 75% that of inner apical spur. All tarsal claws with four strong teeth inside ( Fig. 29H ).

ABDOMEN. Uniform black, glabrous. Abdominal gland absent.

MALE TERMINALIA ( Figs 29D , 30 ). Subgenital plate trapezoidal, covered in short, dense tomentum, with a small, rounded lobe in middle and two sharp lateral processes on posterior edge. Pseudepiphallic sclerite with serrated edges, divaricating at apex.

FEMALE TERMINALIA ( Fig. 29J–K ). Ovipositor short, 30% of body length, strongly curved upwards right from base; light brown in colour. Cross-section of ovipositor quadrilateral at apex, with rows of small, sharp teeth on all four edges.

EGGS ( Fig. 29I ). Cylindrical, smooth, pale yellow in colour, translucent; rounded at one end, with a flat, sticky foot at other end. Dimensions approx. 1.5 mm long and 300 µm wide.

Habitat and ecology

A predatory cricket, diurnal; inhabits uncultivated meadows with tall grass. Not known to make any sound, although it may stridulate by vibrating its maxillary palpi, like the European species Trigonidium (Trigonidium) cicindeloides ( Ingrisch 1977) .

Distribution

New Zealand: widespread in North Island and in the warmer regions of South Island. Not known from Rakiura, Subantarctic Islands or Chatham Islands.

Figures

Fig. 29. Trigonidium (Trigonidium) maoricum (Walker, 1869). A–B. Lateral and frontal views of head, adult ♀. Tumbledown Bay, Banks Peninsula (MPN OR0267). C. Right ♂ forewing, dorsal view. ‘SF’ denotes the stridulum. Tumbledown Bay (MPN OR0268). D. Male sub-genital plate. Kerikeri, Northland (MPN OR0286). E. Stridulatory file. Kerikeri (NZAC03037187). F–G. Anterior and posterior view of tympanum. Kerikeri (NZAC03037187). H. Hind tarsal claw. Tumbledown Bay (MPN OR0268). I. Egg. Waimārama, Hawke’s Bay (MPN OR0327). J. Ovipositor, lateral view. Māhoe Reserve, Lincoln (MPN OR0277). K. Apex of ovipositor, dorsal view. Kerikeri (NZAC03037191). Black scale bars = 500 μm; white scale bars = 100 μm.

Fig. 30. Trigonidium (Trigonidium) maoricum (Walker, 1869), ♂ genitalia. Waimārama, Hawke’s Bay (MPN OR0328). A–C. Microscope images of pseudepiphallic sclerite. A. Dorsal view. B. Ventral view. C. Lateral view. D–F. Micro CT scans, Volume Blending. D. Dorsal view, cross-section. E. Posterior view. F. Lateral view. Scale bars = 250 μm.

Fig. 31. Gene tree for Trigonidium Rambur, 1838 using Maximum Likelihood analysis of ~700 bp of mtDNA (COI) from 23 specimens and 1000 bootstrap replications. The tree with the highest log likelihood (-3571.04) is shown. Numbers next to the branches indicate the percentage of trees in which the associated taxa are clustered together. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. Specimens in blue were collected as part of this study; the remaining 15 sequences were obtained from the GenBank (Benson et al. 2013) and BOLD (Ratnasingham & Hebert 2007) databases. Detailed information for each specimen included in this analysis can be found in Supp. file 1: Table S11.

Fig. 32. Live trigs (subfamily Trigonidiinae). A–D. Trigonidium (Trigonidium) maoricum (Walker, 1869). New Zealand. A. Adult ♂, Tumbledown Bay, Banks Peninsula. B. Adult ♂, Kerikeri, Northland. C. Adult ♀, Māhoe Reserve, Lincoln. D. Fully winged adult ♀. Kerikeri, Northland. E–F. Trigonidium (Trigonidium) australianum (Chopard, 1925). Oxley Creek Commons, Brisbane, QLD, Australia. E. Adult ♀. F. Adult ♂. Note: all specimens are posed on unnatural backgrounds in captivity.

Fig. 38. Map of New Zealand, showing the known distribution of taxa included in this study. Thin black lines indicate the boundaries of Crosby’s entomological regions (Crosby et al. 1998; Fig. 2). Coloured circles indicate the collection localities for the material examined.