Geodorcus ithaginis

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Geodorcus ithaginis
COLE Lucanidae Geodorcus ithaginus.png
Illustration by Des Helmore
Status NZTCS NC.svg
Nationally Critical (NZ TCS)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Lucanidae
Genus: Geodorcus
Species:
G. ithaginis
Binomial name
Geodorcus ithaginis
(Broun, 1893) [1]
Synonyms

Lissotes ithaginis Broun, 1893 [1]

Geodorcus ithaginis, the Mokohinau stag beetle, is a large flightless species of stag beetle in the family Lucanidae. It was described by Thomas Broun in 1893 after being discovered in the Mokohinau Islands by Andreas Stewart Sandager, a lighthouse keeper on the islands. [2] The species survives only on the small unnamed island "Stack H", in a patch of vegetation the size of a living room, and is in extreme danger of extinction.

Contents

Description

Pinned male specimen Mokohinau stag beetle.jpg
Pinned male specimen

Including their large mandibles (used for fighting over mates), male specimens range in length from 25.5 to 32.8 mm and are 10.4–12.4 mm wide. Females range in length from 20.0–22.5 mm. Their exoskeleton is black and ranges from dull to moderately glossy. The thorax is back, glossy, and wider than it is long. The elytra are rounded at the posterior, almost equally long and wide, and covered in short branching hairs. [3] Male beetles have three teeth at the apex of the mandibles; females have two. What distinguishes this species from all other New Zealand stag beetles is a long conical vertical tooth, on the top of the mandible, in both sexes. [4]

Distribution

This species is only known from the Mokohinau Islands in New Zealand. It was one of 130 beetle species collected on the Mokohinaus by lighthouse keeper Andreas Stewart Sandager (stationed on Burgess Island 1883–1889); a third of these species turned out to be new to science, and were described by Thomas Broun. [5] [note 1] The stag beetle's type locality was given by Broun as "Halodroma Islet", but there is no island by that name. "Halodroma" may be another name for Lizard Island, a small flat island southeast of Burgess Island; [4] Halodroma urinatrix is the former name of Pelacanoides urinatrix , the diving petrel, which used to nest in burrows on Lizard and two other low Mokohinau islands. [3]

A few more specimens were collected in 1902, and then none until the species was rediscovered in 1984 on "Stack H", a 1.2 ha island southwest of Burgess Island. [3] [6] All recent surveys have only found this species on Stack H, in a "living-room sized" patch of New Zealand ice plant or horokaka ( Disphyma australe ); [7] it has not been seen on Lizard Island since its description in 1893. [4] [3]

Habitat

Geodorcus species on mainland New Zealand are associated with rotten logs, but these are absent from Stack H. The Mokohinau Islands are generally very arid, with poor moisture retention. [4] This beetle burrows into a peat-like layer of soil formed by New Zealand ice plant (Disphyma australe). It has also been found under rocks, in the tussock grass Chionochloa bromoides, and in the leaf litter beneath coastal pohutukawa. [4]

Diet

These beetles are nocturnal, and their feeding behaviour is unknown. Adult stag beetles worldwide have mouthparts suited to feeding on liquids. Geodorcus helmsi has been seen feeding on sappy exudations on tree trunks. Rotting wood, tree roots or humus are the most common food sources for stag beetle larvae, and G. ithaginis lives in an environment of enriched humus. [3]

Conservation

Searches specifically for G. ithaginis from 1991 to 1994 in the Mokohinau group of islands only found three live beetles on Stack H; nine beetles is the maximum simultaneously observed in recent times. [8] The Mokohinau Islands have been heavily modified by land clearance, burning, grazing, and introduction of the kiore or Polynesian rat; Lizard Island was briefly colonised by kiore in the late 1970s. Rats were eradicated from all the Mokohinau Islands in the 1990s, but subsequent surveys for G. ithaginis on Lizard Island have been unsuccessful. [3] Fire, storms, and rodent introductions are thought to be the most serious threats to this species' survival. Climate change, resulting in a drying out of the island habitat, may also be a threat. [4] The conservation status of this species is categorised as 'nationally critical'. [9] Like other Geodorcus species, this large, slow-moving beetle is protected from collectors under schedule 7 of the 1953 Wildlife Act. [10]

Captive breeding and reintroduction to rat-free islands such as Lizard Island was the Department of Conservation plan for ensuring this species' survival. [7] A expedition in January 2019 thoroughly searched the beetle's habitat on Stack H, another nearby stack, and Lizard Island, and found nothing but fragments of exoskeleton of indeterminate age, and concluded G. ithaginis may possibly be extinct. [6]

Related Research Articles

<span class="mw-page-title-main">Stag beetle</span> Family of insects

Stag beetles are a family of about 1,200 species of beetles in the family Lucanidae, currently classified in four subfamilies. Some species grow to over 12 centimetres, but most to about 5 cm (2 in).

<span class="mw-page-title-main">The Sisters (New Zealand)</span> Northernmost islands of the Chatham archipelago

The Sisters is a group of three main islands located 16 kilometres (10 mi) north of Cape Pattison, Chatham Island. They are the northernmost members of the Chatham Archipelago, located 800 kilometres (497 mi) east of New Zealand's South Island.

<i>Lucanus cervus</i> Species of beetle

Lucanus cervus, known as the European stag beetle, or the greater stag beetle, is one of the best-known species of stag beetle in Western Europe, and is the eponymous example of the genus. L. cervus is listed as Near Threatened by the IUCN Red List.

<i>Lucanus formosanus</i> Species of beetle

Lucanus formosanus is a stag beetle which is endemic to Taiwan, and grows to a length of 45–80 millimetres (1.8–3.1 in). Like other species in the Lucanid family, L. formosanus exhibits distinct sexual dimorphism and subsequent external morphological allometry in males. Males of the species develop mandibles of various forms depending on geographic location; i.e. northern, central, and southern morphs.

<span class="mw-page-title-main">Mokohinau Islands</span> Island group in New Zealand

The Mokohinau Islands (Pokohinau), sometimes spelt Mokohīnau Islands are a small group of islands that lie off the northeast coast of New Zealand's North Island. The islands are 100 km (62 mi) northeast of Auckland, 21 km (13 mi) northwest of Great Barrier Island and approximately 52 km (32 mi) east of Bream Head. The main islands of the group include Fanal Island (Motukino), Burgess Island (Pokohinu), Flax Island (Hokoromea), and Atihau Island. Smaller islands include Bird Rock. Most of them are managed by the Department of Conservation as nature reserves and wildlife sanctuaries. Landing is not allowed without a permit, with the exception of Burgess Island, much of which is managed as a scenic reserve by the Department of Conservation. The remainder of Burgess Island is Crown Land and is administered by the Ministry of Transport. The total land area of the Mokohinau Islands is 160 ha (400 acres).

<i>Paralissotes reticulatus</i> Species of beetle

Paralissotes reticulatus, also called the New Zealand reticulate stag beetle, is a native species of stag beetle from New Zealand. Although they do have wings they are flightless.

<i>Mitophyllus</i> Genus of beetles

Mitophyllus is a genus of large stag beetles endemic to New Zealand.

<i>Mitophyllus parrianus</i> Species of beetle

Mitophyllus parrianus, is a species of stag beetle native to New Zealand. M. parrianus is found throughout the North, South and Stewart Islands of New Zealand.

<i>Geodorcus helmsi</i> Species of beetle

Geodorcus helmsi, known as New Zealand giant stag beetle or Helms's stag beetle, is a large, slow-moving, flightless stag beetle in the family Lucanidae. It is endemic to New Zealand.

<i>Amychus granulatus</i> Species of beetle

Amychus granulatus, commonly known as the Cook Strait click beetle, is a large flightless click beetle in the family Elateridae.

<i>Geodorcus capito</i> Species of beetle

Geodorcus capito is a large flightless species of stag beetle in the family Lucanidae. It is endemic to the Chatham Islands in New Zealand.

<i>Geodorcus alsobius</i> Species of beetle

Geodorcus alsobius, or Moehau stag beetle, is a large flightless species of stag beetle in the family Lucanidae. It is found only on Mt Moehau, the highest mountain in the Moehau Range on the Coromandel Peninsula in New Zealand.

<i>Geodorcus auriculatus</i> Species of beetle

Geodorcus auriculatus is a large flightless stag beetle that is found in the southern part of the Coromandel Peninsula and on Mount Te Aroha in the Kaimai range of New Zealand.

Geodorcus montivagus is a large flightless species of stag beetle in the family Lucanidae. It is known from only one female specimen found on the Victoria Range in New Zealand. It was found in tussock at 1,220 metres (4,000 ft) above sea level.

<i>Geodorcus novaezealandiae</i> Species of beetle

Geodorcus novaezealandiae is a large flightless species of stag beetle in the family Lucanidae. It is the type species and smallest member of the genus Geodorcus. It is endemic to New Zealand.

<i>Geodorcus philpotti</i> Species of beetle

Geodorcus philpotti is a large flightless species of stag beetle in the family Lucanidae. It was named by Major Thomas Broun after Mr A. Philpott, who discovered it at Hump Ridge near Invercargill. It is endemic to New Zealand.

<i>Geodorcus servandus</i> Species of beetle

Geodorcus servandus is a large flightless species of stag beetle in the family Lucanidae. It was discovered by P.R. Kettle in December 1960 and this holotype specimen is held in the New Zealand Arthropod Collection. It was first described by Beverley Holloway in 2007. Its type location is Mount Tuhua summit, near Lake Kaniere on the West Coast of New Zealand. The name servandus is a Latin word meaning "[something] to be preserved, conserved, looked after".

<i>Geodorcus sororum</i> Species of beetle

Geodorcus sororum is a large flightless species of stag beetle in the family Lucanidae. It was discovered in 1973 by Mr. A. Wright on an expedition to Middle Sister Island/Te Awanui, one of The Sisters Islands/Rangitatahi which are part of the Chatham Islands in New Zealand. This holotype specimen is held in the New Zealand Arthropod Collection. It was first described by Beverley Holloway in 2007. The name sororum is translated from Latin to mean "belonging to the sisters".

<i>Paralissotes</i> Genus of beetles

Paralissotes is a genus of stag beetle that is endemic to New Zealand.

<i>Aegus chelifer</i> Species of beetle

Aegus chelifer, is a species of stag beetle found in Indo-Malaya regional countries.

References

  1. 1 2 Broun, Thomas (1893). Manual of the New Zealand Coleoptera. Wellington: New Zealand Institute. p. 1108. Retrieved 22 January 2017.
  2. ↑ Watt, J.C. (1977). "Conservation and type localities of New Zealand Coleoptera, and notes on collectors 1770–1920". Journal of the Royal Society of New Zealand. 7: 79–91. doi: 10.1080/03036758.1977.10419338 .
  3. 1 2 3 4 5 6 Holloway, B.A. "Lucanidae (Insecta: Coleoptera)" (PDF). Landcare New Zealand. Landcare Research. Archived from the original (PDF) on 17 May 2017. Retrieved 11 January 2017.
  4. 1 2 3 4 5 6 McGuiness, C.A. "The Conservation Requirements of New Zealand's Nationally Threatened Invertebrates" (PDF). Department of Conservation. Retrieved 2017-01-22.
  5. ↑ Sandager, F. [sic] (1889). "Observations on the Mokohinou Islands and the Birds which visit them". Transactions and Proceedings of the Royal Society of New Zealand. 22: 286–294.
  6. 1 2 Dickison, Mike (Sep–Oct 2019). "What Happened on Stack H?". New Zealand Geographic. 159.
  7. 1 2 "Ten Most Endangered Species". Endangered Species Foundation. Retrieved 21 February 2017.
  8. ↑ Toki, Nicola; Mulligan, Jesse (17 February 2017). "Critter of the Week: Mokohinau stag beetle". RNZ. Retrieved 21 Feb 2017.
  9. ↑ Stringer, I.A.N; Hitchmough, R.A.; Leschena, R.A.B.; Marris, J.W.M.; Emberson, R.M.; Nunn, J. (2012). "The conservation status of New Zealand Coleoptera". New Zealand Entomologist. 35 (2): 91–98. doi:10.1080/00779962.2012.686311. S2CID   219566068.
  10. ↑ "Wildlife Act 1953". New Zealand Legislation. Parliamentary Counsel Office. Retrieved 25 January 2016.

Notes

  1. ↑ Andreas Fleming Stewart Sandager's name takes various forms in the literature – Andreas Fremming Stewart Sandager, F. S. Sandager, F. Sandager, P. Sandager, and even P. Stewart-Sandager – sometimes appearing two different ways in the same publication. Sandager's wrasse (Coris sandeyeri) takes its species name from another variant of his surname, Sandeyer.
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