''Hemideina crassidens'', commonly known as the Wellington tree wētā, is a large, flightless, nocturnal insect in the family

Anostostomatidae Anostostomatidae is a family of insects in the order Orthoptera, widely distributed in the southern hemisphere. It is named Mimnermidae or Henicidae in some taxonomies, and common names include ''king crickets'' in South Africa and ''wētā'' i ...

. This

wētā Wētā (also spelt weta) is the common name for a group of about 100 insect species in the families Anostostomatidae and Rhaphidophoridae endemic to New Zealand. They are giant flightless crickets, and some are among the heaviest insects in th ...

species 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 ...

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 ...

and populates regions in the southern half of North Island/Te Ika a Maui and the north-west of the South Island/Te Wai Pounamu. They forage arboreally during the night and are most likely

polyphagous Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, or -vorous from Latin ''vorare'', meaning "to devour", or -phage, -phagy, or -phagous from Greek φαγε ...

. There is obvious sexual dimorphism in adults. Individuals are reliant on tree cavities for refuge, social interactions and

mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproduc ...

. The conservation status of ''H. crassidens'' is "not threatened".

Distribution and habitat

''Hemideina crassidens'' is endemic to New Zealand. Populations are distributed between the Ruapehu district and

Wellington Wellington ( mi, Te Whanganui-a-Tara or ) is the capital city of New Zealand. It is located at the south-western tip of the North Island, between Cook Strait and the Remutaka Range. Wellington is the second-largest city in New Zealand by me ...

district of the

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

, and in the

Westland district Westland District is a Districts of New Zealand, territorial authority district on the West Coast, New Zealand, West Coast of New Zealand's South Island. It is administered by the Westland District Council. The district's population is History ...

of the

South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...

. A closely related native

tree wētā Tree wētā are wētā in the genus ''Hemideina'' of the family Anostostomatidae. The genus is endemic to New Zealand. There are seven species within the genus ''Hemideina'', found throughout the country except lowland Otago and Southland. Beca ...

, ''

Hemideina thoracica ''Hemideina thoracica'', commonly known as the Auckland tree wētā or tokoriro is a cricket-like insect (within the family Anostostomatidae). It is endemic to New Zealand and is found over most of the North Island, except for the Wellington re ...

'', is widely distributed in the northern two-thirds of the

. It has been suggested that ''H thoracica'' competitively excludes ''H. crassidens'' from warmer northern regions of the

. On

Mt Taranaki Mount Taranaki (), also known as Mount Egmont, is a dormant stratovolcano in the Taranaki region on the west coast of New Zealand's North Island. It is the second highest point in the North Island, after Mount Ruapehu. The mountain has a secon ...

, ''H. crassidens'' is found only at elevations above ~700 m asl, and ''H. thoracica'' is found lower down the slopes where temperatures are slightly warmer. ''Hemideina crassidens'' is a

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

and arboreal. This species uses holes in tree branches to hide during the day. They usually live in tree holes, suggesting a reliance on forest. However, many extant

populations occupy scrub habitats or even use rock refuges when trees are not available.

Climate change

In the central North Island populations of ''H. crassidens'' have become isolated within areas mostly populated by ''H. thoracica'' suggesting previous range contraction due to interactions with competitors and the environment. This contraction is likely to continue southwards during global warming, resulting in the displacement of ''H. crassidens'' from many lowland areas of central and southern

Diet

Being a

, ''H. crassidens'' spend most of their time foraging arboreally. They are generally

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

, feeding on the leaves, fruit and flowers of a wide range of trees and shrubs. However,

polyphagy Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, or -vorous from Latin ''vorare'', meaning "to devour", or -phage, -phagy, or -phagous from Greek φαγε ...

is common among

species and it is likely that ''H. crassidens'' supplement their

diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...

with animal matter. Individuals have been documented feeding on living or recently dead

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

Morphology

''Hemideina crassidens'' are relatively large at maturity ''(> 6.5 cm body length).'' Their bodies are smooth and shiny, the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

is ringed with contrasting bands of dark brownish to black and yellow, with a pale underside. This colouration is reminiscent of uniform of the Wellington rugby team,

the Hurricanes The Fabulous Hurricanes (formerly The Hurricanes) are a Rhythm and blues, rhythm & blues group originally from Edinburgh, now based in London. The band, currently a four-piece consists of a drummer, James Adam; bassist, Triss Duncan, guitarist ...

, and can be used to distinguish it from the Auckland tree wētā ''(

)''. They have heavily spined hind

tibiae The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

that are used in defence postures.Ordish, R.G. (1992) Aggregation and communication of the Wellington weta Hemideina crassidens (Blanchard) (Orthoptera: Stenopelmatidae). New Zealand Entomologist 15: 1–8. The antennae are long and mobile to help with sensing and navigation, particularly in the dark. The Wellington tree wētā and the Hawkes Bay tree wētā ('' Hemideina trewicki'') look the same but have different numbers of chromosomes. In South Island ''H. crassidens'' have 19 (male) or 20 (female) chromosomes and in North Island this species has 15 or 16 chromosomes. The Hawkes Bay tree wētā has 17 (male) or 18 (female) chromosomes.

Sexual dimorphism

Males display highly exaggerated, positively

allometric Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932. Overview Allom ...

mandibles In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

. Accelerated maturation of males gives rise to three different head sizes that correlate their maturation on either the 8th, 9th or 10th

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...

. 8th

males have small heads, 10th

males have particularly elongated

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

s and a large

vertex Vertex, vertices or vertexes may refer to: Science and technology Mathematics and computer science *Vertex (geometry), a point where two or more curves, lines, or edges meet *Vertex (computer graphics), a data structure that describes the position ...

and 9th

males have an intermediate from. Females only reach maturity at the 10th instar. In this wētā species, females can be identified by their small head and long

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

Galleries

Rather than bore their own tree holes, ''H. crassidens'' inhabit natural crevices and cavities, or pre-existing tunnels that have been excavated by large wood-boring

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

such as '' Aenetus virescens'' (Lepidoptera: Hepoalidae). They prefer tree holes in living timber and avoid fallen or rotten logs.Field, L.H.; Sandlant, G.R. (2001) The gallery-related ecology of New Zealand tree wetas, Hemideina femorata and Hemideina crassidens (Orthoptera, Anostostomatidae). Pp. 243–258 in Field, L.H. (Ed.): The biology of wetas, king crickets and their allies. CABI Publishing, Oxon. Native trees and shrubs such manuka ''(

Leptospermum scoparium ''Leptospermum scoparium'', commonly called mānuka, () mānuka myrtle, New Zealand teatree, broom tea-tree, or just tea tree, is a species of flowering plant in the myrtle family Myrtaceae, native to New Zealand (including the Chatham Islands ...

)'', kanuka ''(

Kunzea ericoides ''Kunzea ericoides'', commonly known as kānuka, kanuka, white tea-tree or burgan, is a tree or shrub in the myrtle family, Myrtaceae and is endemic to New Zealand. It has white or pink flowers similar to those of ''Leptospermum'' and from its ...

)'', ngaio ''(

Myoporum laetum ''Myoporum laetum'', commonly known as ngaio or mousehole tree is a plant in the family Scrophulariaceae endemic to New Zealand, including the Chatham Islands. It is a fast growing shrub, readily distinguished from others in the genus by the tra ...

),''

kohekohe Kohekohe (''Dysoxylum spectabile'') is a medium-sized tree in the Meliaceae family, native to New Zealand. It is found in lowland and coastal forests throughout most of the North Island and also occurs in the Marlborough Sounds in the north ...

''(

Dysoxylum spectabile Kohekohe (''Dysoxylum spectabile'') is a medium-sized tree in the Meliaceae family, native to New Zealand. It is found in lowland and coastal forests throughout most of the North Island and also occurs in the Marlborough Sounds in the north ...

)'' and mahoe ''(

Melicytus ramiflorus ''Melicytus ramiflorus'' (māhoe or whiteywood) is a small tree of the family Violaceae endemic to New Zealand. It grows up to 10 metres high with a trunk up to 60 cm in diameter, it has smooth, whitish bark and brittle twigs. The dark- ...

)'' are favoured by ''H. crassidens''. Suitable galleries have a narrow entrance hole ''(~20mm in diameter)'' in order to provide protection from predators such as

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s. The holes are entered head first and exited in reverse so that the spines on their hind tibiae point outwards to defend from intruders. Inhabited galleries can often be identified by the neatly nibbled entrance which is kept clean. Individuals often occupy the same gallery for an extended period of time. Galleries buffer against environmental variation, especially

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

.Field, L.H.; Sandlant, G.R. (1983) Aggression and mating behaviour in the Stenopelmatidae (Orthoptera; Ensifera), with reference to New Zealand wetas. Pp. 120–146 in Gwynne, D.T.; Morris, G.K. (Eds): Orthopteran mating systems. Sexual competition in a diverse group of insects. Westview Press, Boulder, Colorado, USA.

Breeding

''Hemideina crassidens'' is a

polygynous Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women. Incidence Polygyny is more widespread in Africa than in any ...

insect in which males guard females that reside in tree cavities termed 'galleries'. Galleries are used for breeding and males compete for control of them and access to the females within. Male head size is an indicator of combative ability as the head is used as weaponry in combat for dominance and control of a harem. In cases where the gallery is sufficiently large, multiple males can occupy a single gallery, suggesting that a dominant male defends a harem rather than a gallery per se. Males can avoid combat by facing off, opening their jaws and assessing the gape of their opponent's

. In a non-violent contest the male whose mandibles span the furthest is considered dominant. Small headed males can mate by wandering nocturnally and copulating with females outside of a gallery, or by sneaking into a gallery occupied by a dominant male and copulating with females within. A small headed male is able to control a harem within a gallery if the entrance is too small for large headed males to fit through. Most matings and ovipositions occur over the

summer Summer is the hottest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, the earliest sunrise and latest sunset occurs, daylight hours are longest and dark hours are shortest, wit ...

and

autumn Autumn, also known as fall in American English and Canadian English, is one of the four temperate seasons on Earth. Outside the tropics, autumn marks the transition from summer to winter, in September ( Northern Hemisphere) or March ( Sou ...

. Females lay their eggs vertically in the soil approximately 10mm under the surface. Hatching occurs in

spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a ...

and individuals take about 18 months to become mature, reaching sexual maturity in the following summer. ''Hemideina crassidens'' do not show any parental care. Their normal lifespan is about 3 years, with about 18 months as immatures.

Conservation

The number of suitable galleries in an area is considered to be a major limiting resource of ''H. crassidens.'' The construction and distribution of artificial refuges has been suggested as a possible conservation strategy to try and increase populations of ''H. crassidens'' and ''H. thoracica''.Bleakley C, Stringer I, Robertson A, Hedderley D (2006) Design and use of artificial refuges for monitoring adult tree weta, ''Hemideina crassidens'' and ''H. thoracica.'' Doc Research & Development series 233. Published by Science & Technical Publishing Department of Conservation PO Box 10–420 Wellington, New Zealand. The conservation status of ''H. crassidens'' is "not threatened".Trewick S, Morris S, Johns P, Hitchmough R, Stringer I (2012). The conservation status of New Zealand Orthoptera. New Zealand Entomologist. 35. 10.1080/00779962.2012.686318.

References

External links

{{Taxonbar, from=Q11843923 Weta Insects described in 1851 Anostostomatidae Taxa named by Émile Blanchard