Isoplectron

Isoplectron is a genus of cave wētā in the family Rhaphidophoridae with three species currently recognized.[1] The genus is endemic to New Zealand and distributed throughout the country.

Isoplectron
Isoplectron armatum
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Orthoptera
Suborder: Ensifera
Family: Rhaphidophoridae
Subfamily: Macropathinae
Genus: Isoplectron
Hutton 1896
Species

See text.

Taxonomy and morphology

The genus Isoplectron was described by Hutton in 1896.[2][3] All species in this genus are small in size (10-17mm body length) and are commonly misidentified as a result of increased undescribed species.[4] The fore femora of the Isoplectron does not contain apical spines,[3][5] in addition, the hind tibiae models two pairs of apical spines.[6] Adult females have a broad bilobed subgenital plate[7] while males have a triangular shape.[8] Multiple species are undescribed and are not able to reflect the fauna presently[9] however, descriptions relating to Isoplectron armatum, Isoplectron calcaratum and Isoplectron aciculatum have been made.

Isoplectron armatum

Isoplectron armatum are the most commonly observed species of Isoplectron.[3] They are found across New Zealand but are more concentrated around Dunedin and can be found in dry spaces under bark or in holes of various trees, especially Nothofagus cliffortioides and Kanuka.[9] They are also caught in pitfall traps in southern North Island forests.[10] Their morphology consists of a body length between 11-17mm, short dorsal and laterals in the hind tibial apical spurs,[11] a very small ventral pair of hind tibial apical spurs and no spinules in the hind tarsal plantulae.[11] This is consistent across males and females.

Isoplectron calcaratum
Observations of Isoplectron and their distribution throughout New Zealand

This species overlaps in habitat and morphology with their close relative Isoplectron armatum and have been observed in the north of the South Island and Wellington.[12]

Isoplectron/Setasutum pallidum

Described by Aola Richards in 1972.[13] Limited descriptions and studies have been made on Setasutum pallidum (which might belong in the genus Isoplectron) however they are claimed to be an alpine species with observations in the South Island occurring.[14][13]

Species
  • Isoplectron aciculatum Karny, 1937
  • Isoplectron armatum Hutton, 1897
  • Isoplectron calcaratum Hutton, 1897

Predation

A study conducted by Bremner et al. (1989) compared insect response to disturbance (touch) between individuals living with mammalian predators and those on mammal-free islands.[15] Wētā were observed to jump away or leap off tree branches when disturbed in environments with rodents, but were more likely to move away without haste in environments without rodents. The paper concluded that invertebrate populations, specifically the Isoplectron sp. population in Fiordland, altered their behaviour in environments that contained predators such as stoats (Mustela erminea) and ship rats (Rattus rattus) in comparison to predator free environments.[15] Individuals within the genus Isoplectron are eaten by endemic reptiles such as the Tuatara (Sphenodon), spotted skink (Leiolopisma infrapunctatum) and Pacific geckos (Hoplodactylus pacificus) as well as avian species such as Riflemen (Acanthissitta chloris),[16] Ruru (Ninox novaeseelandiae), Kākā (Nestor meridionalis) and Tieke (Philesturnus).[17]

Conservation

All species within the genus Isoplectron are considered not threatened[6] and are consequently of little conservation concern.[18]

References
  1. "genus Isoplectron Hutton, 1896: Orthoptera Species File". orthoptera.speciesfile.org. Retrieved 2022-09-09.
  2. Hutton, Frederick w. (1896). "The Stenopelmatidæ of New Zealand". Transactions and Proceedings of the Royal Society of New Zealand. 29: 208–243.
  3. Hutton, F. W. (1895). "On a new species of weta (Locustidae) from Bounty Islands". Transactions and Proceedings of the New Zealand Institute. 27: 174–176.
  4. Ho, George Wai-Chun (2013). "Remarks on the GenusNecroscia(Phasmatodea, Diapheromeridae, Necrosciinae) from China, with Two New Records, One New Synonym, and One New Combination and Key to the Species". Journal of Orthoptera Research. 22 (1): 21–27. doi:10.1665/034.022.0104. ISSN 1082-6467. S2CID 85749267.
  5. Fitness, JL; Morgan-Richards, M; Ball, OJ-P; Godfrey, AJR; Trewick, SA (2015-01-02). "Improved resolution of cave weta diversity (Orthoptera: Rhaphidophoridae): ecological implications for Te Paki, Far North, New Zealand". New Zealand Journal of Zoology. 42 (1): 1–16. doi:10.1080/03014223.2014.983939. ISSN 0301-4223. S2CID 55361809.
  6. Trewick, S. A.; Morris, S. J.; Johns, P. M.; Hitchmough, R. A.; Stringer, I. A.N. (2012-06-21). "The conservation status of New Zealand Orthoptera". New Zealand Entomologist. 35 (2): 131–136. doi:10.1080/00779962.2012.686318. ISSN 0077-9962. S2CID 219564547.
  7. Johns, P. M.; Cook, L. D. (2013). "Maotoweta virescens new genus and new species; hidden in a moss forest (Orthoptera: Rhaphidophoridae)". Records of the Canterbury Museum. 27: 11–17.
  8. F., Ward, Darren (1997). "A new generic key to the New Zealand cave weta genera (Orthoptera: Rhaphidophoridae". doi:10.26021/485. {{cite journal}}: Cite journal requires |journal= (help)CS1 maint: multiple names: authors list (link)
  9. "Isoplectron armatum - NZ Biodiversity". nzbiodiversity.com. Retrieved 2022-09-06.
  10. Moeed, Abdul; Meads, M. J. (1987). "Invertebrate survey of offshore islands in relation to potential food sources for the little spotted kiwi, Apteryx oweni (Aves: Apterygidae)". New Zealand Entomologist. 10 (1): 50–64. doi:10.1080/00779962.1987.9722511. ISSN 0077-9962.
  11. Johns, P. M.; Cook, L. D. (2013). "Maotoweta virescens new genus and new species; hidden in a moss forest (Orthoptera: Rhaphidophoridae)". Records of the Canterbury Museum. 27: 11–17.
  12. "Isoplectron cochleatum - NZ Biodiversity". nzbiodiversity.com. Retrieved 2022-09-06.
  13. Richards, Aola M. (June 1972). "Revision of the Rhaphidophoridae (Orthoptera) of New Zealand. Part XIV. Three alpine genera from the South Island". Journal of the Royal Society of New Zealand. 2 (2): 151–174. doi:10.1080/03036758.1972.10429371. ISSN 0303-6758.
  14. "Isoplectron pallidum - NZ Biodiversity". nzbiodiversity.com. Retrieved 2022-09-06.
  15. Bremner, A. G.; Barratt, B. I. P.; Butcher, C. F.; Patterson, G. B. (1989). "The effects of mammalian predation on invertebrate behaviour in South West Fiordland". New Zealand Entomologist. 12 (1): 72–75. doi:10.1080/00779962.1989.9722570. ISSN 0077-9962.
  16. Sherley, Gregory H. (1990). "Co-Operative Breeding in Riflemen (Acanthissitta Chloris) Benefits To Parents, Offspring and Helpers". Behaviour. 112 (1–2): 1–22. doi:10.1163/156853990X00653. ISSN 0005-7959.
  17. Farnworth, Bridgette; Innes, John; Kelly, Catherine; Littler, Ray; Waas, Joseph R. (2018). "Photons and foraging: Artificial light at night generates avoidance behaviour in male, but not female, New Zealand weta". Environmental Pollution. 236: 82–90. doi:10.1016/j.envpol.2018.01.039. ISSN 0269-7491. PMID 29414377. S2CID 46846520.
  18. "NZTCS New Zealand Threat Classification system". nztcs.org.nz. Retrieved 2022-09-09.
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