''Anagotus stephenensis'', commonly known as the ngaio weevil, is a large flightless

weevil Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small – less than in length – and herbivorous. Approximately 97,000 species of weevils are known. They belong to several fa ...

that is only found on Stephens Island in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. The ngaio weevil was discovered in 1916 by A.C. O'Connor on Stephens Island.

Thomas Broun Thomas Broun (; 15 July 1838 – 24 August 1919) was a Scottish-born soldier, farmer, teacher and entomologist, who spent much of his career in New Zealand. He is known for his study of the beetles (Coleoptera) of New Zealand. Broun was born i ...

described it in 1921 as ''Phaeophanus oconnori'' after its collector. The weevils were observed at the time to be 'feeding on tall fescue and the leaves of trees'.

Description

This large weevil has a dark exoskeleton, covered in small hair-like coppery-brown scales. On the sides and posterior, the colouration is lighter with a prominent white streak along the centre of its thorax. It has obvious prominences on its sides and posterior. Its

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

is as long as its thorax with a wide channel in the centre. Including the rostrum, its size ranges from 23 to 27 mm. This weevil is nocturnal and flightless. It is similar in colouration and size and closely related to the

Turbott's weevil Turbott's weevil (''Anagotus turbotti'') is a weevil that is endemic to New Zealand. It has been found on the Hen and Chicken Islands, the Poor Knights Islands and the Three Kings Islands. Taxonomy New Zealand entomologist Donald Spiller first d ...

Distribution

The ngaio weevil has a historic range as far away as

South Canterbury South Canterbury is the area of the Canterbury Region of the South Island of New Zealand bounded by the Rangitata River in the north and the Waitaki River (the border with the Otago Region) to the south. The Pacific Ocean and ridge of the S ...

. The collection of elytra, heads and other body parts in seven cave deposits produced by the extinct

laughing owl The laughing owl (''Ninox albifacies''), also known as ''whēkau'', the laughing jackass, or the white-faced owl, is an Extinction, extinct species of owl that was Endemism, endemic to New Zealand. Plentiful when European settlers arrived in Ne ...

show it was once widespread and common. It has a relict population on Stephens Island.

Habitat

The weevil is known to live on ngaio trees (''Myoporum laetum''), feeding on leaves, where it produces a characteristic feeding notch. The adults have also been found on the karaka tree (''Corynocarpus laevigatus''). Larvae are thought to be woodborers of the same host tree. Larvae of other members of the Aterpini tribe are mostly associated with live wood, boring into stems, leaf bases and roots.

Conservation

This species had its conservation status upgraded to nationally critical in 2012 due to it being found in low numbers in one location. Fifteen specimens were collected by the original expedition in 1916 by A.C. O'Connor. There have not been any specimens collected since 1971 and a devoted search in 1995 found one or two specimens over five nights. This indicates a reduction in population since 1916. The cause of this is likely to be the forest clearance on Stephens Island which caused a reduction in weevil habitat, when a lighthouse was built there in 1892. It is possible that the side-effect of an increase in

tuatara The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...

population after the removal of feral cats in 1925 may have been to reduce the population of the ngaio weevil. The chances of a large, flightless and nocturnal beetle moving from one ngaio tree to another past numerous tuatara and surviving predation is low. It is protected under Schedule 7 of The 1953 Wildlife Act, making it an offense to collect, possess or harm a specimen.

References

External links

*Ngaio weevils discussed on

RNZ Radio New Zealand (), commonly known as RNZ or Radio NZ, is a New Zealand public service broadcaster and Crown entity. Established under the Radio New Zealand Act 1995, it operates news and current affairs station, RNZ National, and a classica ...

Critter of the Week ''Critter of the Week'' is a weekly RNZ National programme about endangered and neglected native plants and animals of New Zealand. Beginning in 2015, ''Critter of the Week'' is an approximately 15-minute discussion between Nicola Toki (origi ...

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13 December 2019
{{Taxonbar, from=Q4750847 Endangered biota of New Zealand Endemic beetles of New Zealand Cyclominae Beetles described in 1982