''Geodorcus capito'' is a large flightless species of

stag beetle Stag beetles are a family of about 1,200 species of beetles in the family Lucanidae, currently classified in four subfamilies.Smith, A.B.T. (2006). A review of the family-group names for the superfamily Scarabaeoidea (Coleoptera) with corrections ...

in the family Lucanidae. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the

Chatham Islands The Chatham Islands ( ) (Moriori: ''Rēkohu'', 'Misty Sun'; mi, Wharekauri) are an archipelago in the Pacific Ocean about east of New Zealand's South Island. They are administered as part of New Zealand. The archipelago consists of about te ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Description

The exoskeleton of ''Geodorcus capito'' varies in colour from glossy black to brownish black. Adults show distinct

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. Including mandibles, male beetles range in length from 17.0–27.0 mm; females from 15.0–19.5 mm. Male and female beetles can be distinguished by the distinct ribbed elytra with obvious branching

setae In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. Th ...

on the male beetle, whilst a female beetle has more vague ribbed elytra and barely visible setae.

Distribution

This stag beetle is found throughout the Chatham Islands, including on Chatham Island, Pitt Island,

Rangatira In Māori culture, () are tribal chiefs, the hereditary Māori leaders of a hapū. Ideally, rangatira were people of great practical wisdom who held authority () on behalf of the tribe and maintained boundaries between a tribe's land and that ...

, Mangere Island and

Little Mangere Island Little Mangere is a small island of the Chatham Archipelago, just off the western end of Mangere Island, about 4 km (2½ mi) west of Pitt Island and south-east of the town of Waitangi on Chatham Island. The island is called ''Tapuaenuku'' ...

. It is now thought to be restricted to the southern end of Chatham Island and is less common on Pitt Island than previously. It is possible that vulnerable species like ''G. capito'' have been restricted in their distribution by grazing and habitat loss on Chatham Island and pig rooting on Pitt Island.

Habitat

All ''Geodorcus'' are nocturnal forest species. Adult ''G. capito'' beetles have been seen at night on the ground and on trees. During the day, beetles can be seen hiding under rotten branches and inside debris on tree trunks. All life cycle stages, including eggs, have been seen in moss covered cavities of trees on Chatham Island. On smaller islands adults have been collected under rocks in coastal forest.

Diet

From their mouthparts, it is assumed that all adult stag beetles are liquid feeders. Adult ''Geodorcus'' beetles feed on sappy exudations from trees. Stag beetle larvae consume rotting wood at or above ground but a few species live underground and feed on either roots or humus.

Conservation

Like other ''Geodorcus'' species, ''G. capito'' is protected under Schedule 7 of The 1953 Wildlife Act, making it an offense to collect or harm a specimen. The Chatham Island stag beetle has suffered a large reduction in its range on the inhabited Chatham Islands.

References

External links

Citizen Scientists observations of ''Geodorcus capito''.
{{Taxonbar, from=Q680774 Beetles described in 1873 Lucaninae Beetles of New Zealand Endemic fauna of New Zealand Fauna of the Chatham Islands Endemic insects of New Zealand