Pteronemobius cf. arima Otte & Alexander, 1983

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 : 52-57

Pteronemobius cf. arima Otte & Alexander, 1983

Figs 6–7 , 8C–D , 25–26 , 27G–L , 28D–F , 38F

Diagnosis

A small ground cricket (body length 4 to 6 mm), coloured brown, with individual variation from light reddish/brown to almost black. Three subapical spurs on outer edge of Tibia III in both males and females; three subapical spurs on inner edge in females, four in males, the fourth spur being glandular. Male forewing dark with a pale stripe running along the edges; upper surface of wing is textured, matt ( Fig. 8C–D ); stridulatory file with 75 to 130 teeth. Female forewing with both short ( Fig. 28F ) and long ( Fig. 28E ) morphs; individuals with fully developed hindwings common.

Material examined (see also Supp. file 1: Table S7 )

NEW ZEALAND – Taranaki (TK) • 1 ♂; Bell Block, New Plymouth ; 39.02408° S, 174.14423° E; 20 m a.s.l.; 30 Mar. 2022; D. Hegg leg.; in grass; insect net; MPN OR0249 • 1 ♂; Bell Block, New Plymouth ; 39.02314° S, 174.14505° E; 20 m a.s.l.; 31 Mar. 2022; D. Hegg leg.; in grass; insect net; MPN OR0250 • 1 ♂; Awakino Gorge ; 38.62087° S, 174.74416° E; 130 m a.s.l.; 19 Mar. 2024; D. Hegg leg.; in lawn; trowel and jar; MPN OR0325 . – Taupō ( TO) • 1 ♂, 2 ♀♀; Taumarunui ; 38.88301° S, 175.26033° E; 200 m a.s.l.; 2 Apr. 2022; D. Hegg leg.; in lawn; jar; MPN OR0252 to OR0254 . – Coromandel / Bay of Plenty (CL/ BP) • 1 ♀; Waihi ; 37.39444° S, 175.84915° E; 100 m a.s.l.; 12 Apr. 2023; D. Hegg leg.; on footpath; insect net; MPN OR0251 . – Auckland (AK) • 2 ♂♂, 1 ♀; Avondale Motor Park, Auckland ; 36.89795° S, 174.70778° E; 40 m a.s.l.; 28 Mar. 2022; D. Hegg leg.; on sparsely vegetated ground; jar; MPN OR0256 to OR0258 . – Northland (ND) • 1 ♂; Whangārei ; 35.70408° S, 174.3532° E; 100 m a.s.l.; 1 Aug. 2023; D. Hegg leg.; in car park; jar; MPN OR0255 • 1 ♂, 1 ♀; Kerikeri ; 35.24029° S, 173.93822° E; 100 m a.s.l.; 22 Mar. 2022; D. Hegg leg.; in tall grass; insect net; MPN OR0223 , OR0234 • 5 ♂♂, 10 ♀♀; Kerikeri ; 35.22795° S, 173.94853° E; 50 m a.s.l.; 21 Mar. 2022; D. Hegg leg.; on footpath; jar; MPN OR0224 to OR0233 , OR0235 to OR0239 • 1 ♂; Springbank Rd, Kerikeri ; 35.24249° S, 173.92505° E; 100 m a.s.l.; 1 Apr. 2024; D. Hegg leg.; in lawn; jar; MPN OR0385 • 1 ♀; Mahinepua Peninsula Track ; 34.99595° S, 173.84891° E; 20 m a.s.l.; 30 Apr. 2021; D. Hegg leg.; short grass on walking track; insect net; MPN OR0482 • 4 ♂♂, 4 ♀♀; Maitai Bay, Karikari Peninsula ; 34.82342° S, 173.40619° E; 30 m a.s.l.; 5 Dec. 2022; D. Hegg leg.; in grass; trowel and jar; MPN OR0240 to OR0247 • 7 ♂♂, 4 ♀♀; same data as for preceding; 28 Mar. 2024; MPN OR0359 to OR0369 • 1 ♀; Kapowairua campsite, Spirits Bay ; 34.42586° S, 172.86203° E; 10 m a.s.l.; 25 Mar. 2022; D. Hegg leg.; in grass; jar; MPN OR0248 .

Description

A detailed description of Pteronemobius cf. arima is not included here, since I am not designating or describing a new species, nor would I know how to differentiate it from P. arima proper, assuming it is different at all. Images of the main characters are in Figs 8D , 25 and 27G–L.

MEASUREMENTS. See Table 6 , also Figs 6–7 . No sexual dimorphism.

SONG. A very quiet sequence of chirps, rather like a mere whisper, difficult to record. Peak frequency between 6 kHz and 7 kHz, each chirp approx. 0.2 seconds in length; interval between chirps between 0.4 and 0.7 seconds long. Pulse rate approx. 40 pulses per second. See also Fig. 26 and Table 6 .

Habitat and ecology

Pteronemobius cf. arima is a nocturnal species, more tolerant of dry conditions than P. truncatus . It inhabits a variety of grassland habitats, including swamp, rank grass, lawns and sports fields.

Pteronemobius cf. arima often forms mixed populations with the larger Pteronembius truncatus and with ground crickets in the genus Bobilla , with which it could easily be confused.

Distribution

Native of Australia, region unknown. New Zealand: relatively common in northern half of North Island ( Fig. 38F ).

Figures

Fig. 6. Morphometric measurements for the New Zealand species of Pteronemobius Jacobson, 1904. This figure replicates Otte & Alexander (1983: fig. 129). Measurements for the Australian specimens of P. truncatus (Saussure, 1877) and of P. arima Otte & Alexander, 1983 were extracted from Otte & Alexander (1983). Measurements for the New Zealand specimens of P. truncatus and of P. cf. arima are from the materials examined in this study. A. Relationship between pronotum length and hind femur length in males of Pteronemobius (Otte & Alexander 1983: fig. 129a–b). B. Relationship between ovipositor length and hind femur length in females of Pteronemobius (Otte & Alexander 1983: fig. 129c).

Fig. 7. Morphometric measurements for the New Zealand species of Pteronemobius Jacobson, 1904. In all graphs, orange shapes indicate P. cf. arima Otte & Alexander, 1983; yellow shapes indicate P. truncatus (Saussure, 1877). Both sexes are included unless stated otherwise. A. Boxplot of the ratio of the short and long diagonals in the right male forewing’s posterior cell of the harp (see Fig. 1B). The whiskers include the minimum and maximum values. B. Stridulatory file in male cricket’s right forewing. C. Dimensions of male cricket’s right forewing (Fig. 1B). D. Body length vs ovipositor length (Fig. 1D). E. Major vs minor axis of tympanum (Fig. 1E). For each cricket, the measurements of both left and right tympana are included. F. Length of middle vs dorsal inner apical spurs on tibia III (Fig. 1A).

Fig. 8. Dorsal view of the right forewing in the New Zealand species of Pteronemobius Jacobson, 1904. A–B. Pteronemobius truncatus (Saussure, 1877). A. Drawing from Otte & Alexander (1983: fig. 132b). B. Kohuroanaki Loop Track, Te Paki (MPN OR0197). C. Pteronemobius arima Otte & Alexander, 1983. Drawing from Otte & Alexander (1983: fig. 132m). D. Pteronemobius cf. arima Otte & Alexander, 1983. Maitai Bay, Karikari Peninsula, Northland (MPN OR0246). Scale bars = 1 mm.

Fig. 25. Pteronemobius cf.arima Otte &Alexander, 1983. A–B. Lateral and frontal view of head, adult♀. A. Spirits Bay, Northland (MPN OR0248). B. Kerikeri, Northland (MPN OR0223). C. Glandular subapical spur (tsai4) on dorsal inner edge of tibia III in adult ♂. Kerikeri (MPN OR0234). D. Egg. Maitai Bay, Northland (MPN OR0366). E–F. Apex of ovipositor. Spirits Bay (MPN OR0248). E. Dorsal view. F. Lateral view. G. Ovipositor, lateral view. Kerikeri (MPN OR0225). Scale bars = 500 μm.

Fig. 26. Pteronemobius cf. arima Otte & Alexander, 1983 song, recorded in the field at 18°C. Maitai Bay, Karikari Peninsula. A. Spectrogram of a sequence of six chirps. B. Oscillogram of a sequence of six chirps. C. Oscillogram of one chirp consisting of eleven pulses. D. Power spectrum of one chirp.

Fig. 27. Pteronemobius Jacobson, 1904, ♂ genitalia of New Zealand species. A–F. Pteronemobius truncatus (Saussure, 1877). Cambridge, Waikato. A–C. Microscope images of pseudepiphallic sclerite (MPNOR0344).A. Dorsal view.B. Ventralview.C. Lateral view.D–F. Micro CT scans,Volume Blending (MPN OR0345). D. Dorsal view. E. Ventral view, cross-section. F. Dorso-lateral view (45º angle). G–L. Pteronemobius cf. arima Otte & Alexander, 1983. G–H. Microscope images of pseudepiphallic sclerite. Maitai Bay, Northland (MPN OR0359). G. Dorsal view. H. Ventral view. I–L. Micro CT scans, Volume Blending. Kerikeri, Northland (MPN OR0385). I. Lateral view. J–K. Dorsal view. L. Dorsolateral view (45º angle). Scale bars = 250 μm.

Fig. 28. Live Pteronemobius Jacobson, 1904. A–C. Pteronemobius truncatus (Saussure, 1877). A. Adult ♂, Kohuroanaki Loop Track, Te Paki, Northland. B. Adult ♀ with short forewings. Awakino, Waikato. C. Fully winged adult ♀. Leitchs Clearing, Herangi Range. D–F. Pteronemobius cf. arima Otte & Alexander, 1983. D. Adult ♂, Auckland. E. Fully winged adult ♀. Kerikeri, Northland. F. Adult ♀ with short forewings. Kerikeri, Northland. 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.