Anagotus Fairburni
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''Anagotus fairburni'' or Flax 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 ...
. It feeds on leaves of New Zealand flax species where it produces a characteristic feeding notch. It is found on islands and in alpine areas of New Zealand.


Taxonomy and description

The flax weevil was described by Albert E. Brookes in 1932 based on a series of specimens sent to him by Ernest Richard Fairburn. These were collected at its type locality of
D'Urville Island D'Urville Island (), Māori name ', is the largest island in the Marlborough Sounds, on the northern coast of the South Island of New Zealand. It was named after the French explorer Jules Dumont d'Urville. With an area of approximately , it is ...
in the
Marlborough Sounds The Marlborough Sounds (Māori language, te reo Māori: ''Te Tauihu-o-te-Waka'') are an extensive network of ria, sea-drowned valleys at the northern end of the South Island of New Zealand. The Marlborough Sounds were created by a combination ...
in 1931. The type specimen is held at the
New Zealand Arthropod Collection The New Zealand Arthropod Collection is a collection of terrestrial invertebrates held by Maanaki Whenua – Landcare Research in Auckland, New Zealand. It specialises in the taxonomy and identification of indigenous and exotic invertebrate sp ...
. It was described as large and robust in form and ranging in size from 20–24mm. Specimens can range in colour from coppery-brown to dark brown, or even black in older weevils that have lost their scales. They have distinctive pairs of
tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projectio ...
s mid-way along and at the base of the
elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...
. Larvae are large with a cream coloured body and brown head. The adult is flightless.


Distribution and habitat

This species is distributed across a wide range. It can be located from the
Three Kings Islands 3 (three) is a number, numeral (linguistics), numeral and numerical digit, digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cul ...
, north of the
North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...
of New Zealand, to Coal Island in
Fiordland Fiordland (, "The Pit of Tattooing", and also translated as "the Shadowlands"), is a non-administrative geographical region of New Zealand in the south-western corner of the South Island, comprising the western third of Southland. Most of F ...
off the southern coast of the
South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
. Between these locations are numerous populations on islands in the Marlborough Sounds. On islands, it is usually found on New Zealand flax/harakeke (''
Phormium tenax ''Phormium tenax'' (called flax in New Zealand English; in Māori language, Māori; New Zealand flax outside New Zealand; and New Zealand hemp in historical nautical contexts) is an evergreen perennial plant native to New Zealand and Norfolk I ...
''). It is restricted to rodent-free islands and alpine areas. In the
Tararua Range The Tararua Range, often referred to as the Tararua Ranges or Tararua, is one of several mountain ranges in the North Island of New Zealand. The Tararua Range runs northeast–southwest for from near Palmerston North to the upper reaches of ...
and on islands in
Dusky Sound Tamatea / Dusky Sound is a fiord on the southwest corner of New Zealand, in Fiordland National Park. Geography One of the most complex of the many fiords on this coast, it is also the largest at 40 kilometres in length and eight kilometres wi ...
it lives on mountain flax/wharariki (''
Phormium colensoi ''Phormium colensoi'' (syn. ''Phormium cookianum'' – see below), also called mountain flax, or in Māori, is a perennial plant that is endemic to New Zealand. The greenish, yellow or orange flowers are followed by twisted seed pods. It is le ...
).'' All life cycle stages are found on or near flax.


Behaviour and host species

Adults are nocturnal and hide among the dead flax leaves at the base of a plant during the day, emerging at night to feed. Their feeding damage is smooth ovoid notching of the leaf edges; the asymmetrical notches are fibrous and rough, unlike the smooth notches left by the flax notch caterpillar '' Tmetolophota steropastis''. Eggs are deposited at the bases of leaves. Larvae feed by burrowing into flax roots. If disturbed at night, flax weevils characteristically drop from flax leaves onto the ground or stay motionless on leaves.


Life cycle

White eggs are laid at the base of flax plants. These eggs can take from 3 to 5 weeks to develop into larvae. They gradually darken to a black colour prior to the larvae emerging. The yellow larvae move towards the fan of leaves near the plant base, where they tunnel into the soft tissue within. The timing of the larval or pupal stages are unknown. Adult flax weevils have lived for over 12 months in captivity.


Conservation and threats

The flax weevil is legally protected under Schedule 7 of the 1953 Wildlife Act, making it an offence to collect, possess or harm a specimen. Predation by rats and mice has caused a restriction of their range to predator-free islands and alpine areas; historically, their range was throughout New Zealand. Translocations have occurred to islands, once rodents have been removed. These include Breaksea Island in Fiordland, Titi Island in the Marlborough Sounds, and Mana Island off the south-west coast of the North Island.


Research

Damage to flax plants is usually minimal, but on Mana Island the translocated population has caused the collapse and death of flax plants around the release site. The flax plants on Mana Island are being studied to see if they are more susceptible to flax weevil browsing, with field trials of flax plantings from different sources. The absence of the fungus ''
Beauveria ''Beauveria'' is a genus of asexually-reproducing fungi allied with the ascomycete family Cordycipitaceae. Its several species are typically insect pathogens. The sexual states ( teleomorphs) of ''Beauveria'' species, where known, are species ...
'' was suggested as a reason for the lack of bio-control of flax weevils on Mana, but this
entomopathogenic fungus Entomopathogenic fungi are parasitic unicellular or multicellular microorganisms belonging to the kingdom of Fungi, that can infect and seriously disable or kill insects. Pathogenicity for insects is widely distributed in the kingdom of fungi and ...
turns out to be already present on the island.


References


External links

*Flax 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 ...
''
29 March 2019
{{Taxonbar, from=Q16982060 Endemic beetles of New Zealand Cyclominae Beetles described in 1932