Weta
Encyclopedia
Weta is the name given to about 70 insect
species
endemic
to New Zealand
. There are many similar species around the world, though most are in the southern hemisphere. The name comes from the Māori
word 'wētā' and is the same in the plural (like 'sheep'). The Māori word for the Giant Weta is 'wētā punga' (lumpy or jointed weta).
, but the hind legs
are enlarged and usually very spiny. Many are wingless. Because they can cope with variations in temperature, weta are found in a variety of environments including alpine, forests, grasslands, caves, shrub lands and urban gardens. They are nocturnal and all New Zealand species are flightless. Different species have different diets. Most weta are predators or omnivores preying on other invertebrates, but the tree and giant weta eat mostly lichens, leaves, flowers, seed-heads and fruit.
Weta can bite with powerful mandibles. Tree weta bites are painful but not particularly common. Weta can inflict painful scratches, with the potential of infection
, but their defence displays consist of looking large and spiky, and they will retreat if given a chance. Tree weta arc their hind legs into the air in warning to foes and then strike downwards so that the spines could scratch the eyes of a predator. Pegs or ridges at the base of the abdomen are struck by a patch of fine pegs at the base (inner surface) of the legs and this action makes a distinctive sound. These actions are also used in defence of a gallery by competing males. The female weta looks as if she has a stinger, but it is an ovipositor, which enables her to lay eggs inside rotting wood or soil. Some species of Hemiandrus have very short ovipositors, related perhaps to their burrowing into soil and laying their eggs in a special chamber at the end of the burrow.
New Zealand had no land mammals (apart from native bats) before humans arrived, and ecological niches occupied by mammals in other parts of the world were taken by non-mammals. The weta’s place in the ecosystem
is comparable to that held by mice and other rodent
s elsewhere in the world. For example, they are hunted by an owl, the morepork
, New Zealand’s only surviving native owl
. Weta pass seeds of some plant species through their digestive tracts unharmed, thus acting as effective seed dispersers. It is yet to be seen how decreases in weta populations are affecting native plant species that may rely on the weta's help.
The weta's lifestyle and habitat, where it may choose to remain concealed in suburban environments until unexpectedly confronted, combined with its notoriously unfriendly appearance, make it a frequent victim of irrational human aggression.
Giant, tree, ground, and tusked weta are all members of the family
Anostostomatidae
(formerly in the Stenopelmatidae, but recently separated (Johns, 1997)). Cave weta are members of the family Rhaphidophoridae
called cave crickets or camel crickets elsewhere, in a different Ensifera
n superfamily.
There are 11 species of giant weta (Deinacrida spp.), most significantly larger than other weta, which are themselves large by insect standards. They are heavy insects with a body length of up to 100 mm (4 in) not inclusive of their lengthy legs and antennae
, and weigh about 20–30 g. A captive giant weta (Deinacrida heteracantha) filled with eggs reached a record 70 g, making it one of the heaviest documented insects in the world and heavier than a sparrow
. The largest species of giant weta is the Little Barrier Island weta, also known as the wetapunga. Giant weta tend to be less social and more passive than other weta. They are classified in the genus
Deinacrida, which is Greek for terrible grasshopper. They are found primarily on small islands off the coast of the main islands, and are examples of island gigantism
.
There are seven species of tree weta:
Mountain stone weta can survive being frozen for months in a state of suspended animation down to temperatures of -10°C. This is because their haemolymph (the insect equivalent of blood) contains special proteins that prevent ice from forming in their cells. It also has the behaviour of "playing dead", by lying still for a short time on its back with legs splayed and claws exposed and jaws wide open ready to scratch and bite.
When the territories of species overlap, as with the related species H. femorata and H. ricta on Banks Peninsula, they may interbreed, although offspring are sterile.
monstrosus, now named Anisoura nicobarica; the Middle Island tusked weta Motuweta isolata; and a newly-discovered Raukumara tusked weta, Motuweta riparia. The Northland tusked weta lives in tree holes similar to tree weta. The Middle Island tusked weta, also called the Mercury Island
tusked weta after the islands on which it lives, was discovered in 1970. It is a ground-dwelling weta, covering its shallow burrows with leaves. The Middle Island weta is the most endangered weta species and a Department of Conservation breeding programme is establishing new colonies on other islands of the Mercury Island group. The Raukumara was discovered in 1996, in the Raukumara Range
near the Bay of Plenty
. There are probably more species still to be identified.
. There are about 40 species of ground weta in New Zealand and several very similar ones in Australia. There are also very like the Californian Cnemotettix—a similarity perhaps due to their very similar habits and habitat. Most of the Hemiandrus have not been described. They hide in burrows in the ground during the day and those that live in open ground (e.g., H. focalis) conceal the exit hole with a specially made perforated door. During the night ground weta hunt invertebrate prey and eat fruit.
and organs on the antennae are also sensitive to low frequency vibrations in the air. Cave weta may be active within the confines of their caves during the daytime, and those individuals close to cave entrances venture outside at night. But most species are forest dwellers and a few are to be found in the high alpine screes living among the broken rock that are covered with snow up to six months of the year. New Zealand species are classified in several genera in subfamily Macropathinae of family Rhaphidophoridae
, and are very distant cousins of the other types of weta.
and kiwi
), reptiles and bats before the arrival of humans, introduced species such as cats, hedgehogs, rats (including kiore) and mustelids
have caused a sharp increase in the rate of predation. They are also vulnerable to habitat destruction caused by humans and modification of their habitat caused by introduced browsers. New Zealand’s Department of Conservation considers that 16 of the 70 species of weta are now at risk. Programmes to prevent extinctions have been implemented since the 1970s.
Some examples of especially endangered species are even tracked by radio beacons.
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. There are many similar species around the world, though most are in the southern hemisphere. The name comes from the Māori
Maori language
Māori or te reo Māori , commonly te reo , is the language of the indigenous population of New Zealand, the Māori. It has the status of an official language in New Zealand...
word 'wētā' and is the same in the plural (like 'sheep'). The Māori word for the Giant Weta is 'wētā punga' (lumpy or jointed weta).
General characteristics
Many weta are large by insect standards and some species are among the largest and heaviest in the world. Their physical appearance is like a katydid or long-horned grasshopper or a cricketCricket (insect)
Crickets, family Gryllidae , are insects somewhat related to grasshoppers, and more closely related to katydids or bush crickets . They have somewhat flattened bodies and long antennae. There are about 900 species of crickets...
, but the hind legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
are enlarged and usually very spiny. Many are wingless. Because they can cope with variations in temperature, weta are found in a variety of environments including alpine, forests, grasslands, caves, shrub lands and urban gardens. They are nocturnal and all New Zealand species are flightless. Different species have different diets. Most weta are predators or omnivores preying on other invertebrates, but the tree and giant weta eat mostly lichens, leaves, flowers, seed-heads and fruit.
Weta can bite with powerful mandibles. Tree weta bites are painful but not particularly common. Weta can inflict painful scratches, with the potential of infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
, but their defence displays consist of looking large and spiky, and they will retreat if given a chance. Tree weta arc their hind legs into the air in warning to foes and then strike downwards so that the spines could scratch the eyes of a predator. Pegs or ridges at the base of the abdomen are struck by a patch of fine pegs at the base (inner surface) of the legs and this action makes a distinctive sound. These actions are also used in defence of a gallery by competing males. The female weta looks as if she has a stinger, but it is an ovipositor, which enables her to lay eggs inside rotting wood or soil. Some species of Hemiandrus have very short ovipositors, related perhaps to their burrowing into soil and laying their eggs in a special chamber at the end of the burrow.
New Zealand had no land mammals (apart from native bats) before humans arrived, and ecological niches occupied by mammals in other parts of the world were taken by non-mammals. The weta’s place in the ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
is comparable to that held by mice and other rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s elsewhere in the world. For example, they are hunted by an owl, the morepork
Southern Boobook
The Southern Boobook , also called the Mopoke, Morepork, Ruru or Tasmanian Spotted Owl, is a small brown owl found throughout New Zealand, Tasmania, across most of mainland Australia and in Timor, southern New Guinea and nearby islands.The bird has almost 20 alternative common names, most of which...
, New Zealand’s only surviving native owl
Owl
Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...
. Weta pass seeds of some plant species through their digestive tracts unharmed, thus acting as effective seed dispersers. It is yet to be seen how decreases in weta populations are affecting native plant species that may rely on the weta's help.
The weta's lifestyle and habitat, where it may choose to remain concealed in suburban environments until unexpectedly confronted, combined with its notoriously unfriendly appearance, make it a frequent victim of irrational human aggression.
Taxonomy and evolution
Fossilized orthoptera have been found in Russia, China, South Africa, Australia and New Zealand, but the relationships are very open to different interpretations. Certainly most weta of both families are in the southern hemisphere lands. Pratt, Morgan-Richards and Trewick think that weta were present in ancient Gondwanaland before New Zealand separated from it although it is also possible they dispersed as they must have done so to colonise New Caledonia and the Chatham Islands. Although they are of an ancient lineage the present species are quite young which conflicts with those earlier ideas about dispersal of weta forebears around the southern hemisphere (Wallis et al. 2000).Giant, tree, ground, and tusked weta are all members of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Anostostomatidae
Anostostomatidae
Anostostomatidae is a family in the order Orthoptera. It is sometimes referred to as Mimnermidae or Henicidae in some taxonomies, and common names include King crickets in South Africa, and wetas in New Zealand. They are believed to be most closely related to the Jerusalem crickets of North America...
(formerly in the Stenopelmatidae, but recently separated (Johns, 1997)). Cave weta are members of the family Rhaphidophoridae
Rhaphidophoridae
The orthopteran family Rhaphidophoridae includes the cave wetas, cave crickets, camelback crickets, camel crickets, spider crickets and sand treaders, of the suborder Ensifera; in some regions, such as Missouri and Virginia, these crickets are referred to as "Cricket Spiders"...
called cave crickets or camel crickets elsewhere, in a different Ensifera
Ensifera
Ensifera is a suborder of the order Orthoptera, comprising insects commonly known as crickets, katydids and bush crickets. "Ensifer" means "sword bearer" in Latin, and refers to the typically elongated and blade-like ovipositor of the females...
n superfamily.
Giant weta
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
, and weigh about 20–30 g. A captive giant weta (Deinacrida heteracantha) filled with eggs reached a record 70 g, making it one of the heaviest documented insects in the world and heavier than a sparrow
Sparrow
The sparrows are a family of small passerine birds, Passeridae. They are also known as true sparrows, or Old World sparrows, names also used for a genus of the family, Passer...
. The largest species of giant weta is the Little Barrier Island weta, also known as the wetapunga. Giant weta tend to be less social and more passive than other weta. They are classified in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Deinacrida, which is Greek for terrible grasshopper. They are found primarily on small islands off the coast of the main islands, and are examples of island gigantism
Island gigantism
Island gigantism or insular giantism is a biological phenomenon in which the size of animals isolated on an island increases dramatically in comparison to their mainland relatives....
.
Tree weta
Tree weta (Hemideina) are those most commonly encountered in suburban settings in the North Island. They are up to 40 mm long and most commonly live in holes in trees formed by beetle and moth larvae or where rot has set in after a twig has broken off. The hole, called a gallery, is maintained by the weta and any growth of the bark surrounding the opening is chewed away. They readily occupy a preformed gallery in a piece of wood (a weta motel) and can be kept in a suburban garden as pets. A gallery might house a harem of up to ten juveniles of both sexes, females and one male. Tree weta are nocturnal. Their diet consists of plants and small insects. The males, which usually have much larger jaws than the females, hiss and bite when threatened.There are seven species of tree weta:
- The Auckland tree weta Hemideina thoracica (also called tokoriro) can be found throughout the North IslandNorth IslandThe North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
apart from the WellingtonWellingtonWellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...
-WairarapaWairarapaWairarapa is a geographical region of New Zealand. It occupies the south-eastern corner of the North Island, east of metropolitan Wellington and south-west of the Hawke's Bay region. It is lightly populated, having several rural service towns, with Masterton being the largest...
region. - The Wellington tree weta H. crassidens occupies Wellington, the Wairarapa, the northern parts of South IslandSouth IslandThe South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
, and the West CoastWest Coast, New ZealandThe West Coast is one of the administrative regions of New Zealand, located on the west coast of the South Island, and is one of the more remote and most sparsely populated areas of the country. It is made up of three districts: Buller, Grey and Westland...
.- H. crassidens crassicruris was described from Stephens Island but is now recognized as H. crassidens.
- H. trewicki in Hawke's BayHawke's BayHawke's Bay is a region of New Zealand. Hawke's Bay is recognised on the world stage for its award-winning wines. The regional council sits in both the cities of Napier and Hastings.-Geography:...
. - H. femorata in Marlborough and CanterburyCanterbury, New ZealandThe New Zealand region of Canterbury is mainly composed of the Canterbury Plains and the surrounding mountains. Its main city, Christchurch, hosts the main office of the Christchurch City Council, the Canterbury Regional Council - called Environment Canterbury - and the University of Canterbury.-...
. - A rare H. ricta species in Banks PeninsulaBanks PeninsulaBanks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately and encompasses two large harbours and many smaller bays and coves...
. - The West Coast bush weta H. broughi largely overlaps with the Wellington tree weta in Nelson and the northern portion of the West Coast.
- H. maori, the mountain stone weta, lives in the drier areas of the South Island high country from the Kaikoura Ranges south to Rock and Pillar Range near Dunedin. At most sites it lives on the ground, under stones or in crevices but in at least two island (within lakes) sites which have not been modified greatly it happily lives both in trees and on the ground.
Mountain stone weta can survive being frozen for months in a state of suspended animation down to temperatures of -10°C. This is because their haemolymph (the insect equivalent of blood) contains special proteins that prevent ice from forming in their cells. It also has the behaviour of "playing dead", by lying still for a short time on its back with legs splayed and claws exposed and jaws wide open ready to scratch and bite.
When the territories of species overlap, as with the related species H. femorata and H. ricta on Banks Peninsula, they may interbreed, although offspring are sterile.
Tusked weta
Tusked weta are distinctive because of the males having long curved tusks projecting forward from their jaws. The tusks are used to push an opponent; they are not used for biting. The females are similar to ground weta. Tusked weta are mainly carnivorous, eating worms and insects. They consist of three species: the Northland tusked weta HemiandrusHemiandrus
Hemiandrus is a genus of weta in the family Anostostomatidae. They are endemic to New Zealand and are known as ground wetas.-Species:* Hemiandrus bilobatus Ander, 1938* Hemiandrus fiordensis...
monstrosus, now named Anisoura nicobarica; the Middle Island tusked weta Motuweta isolata; and a newly-discovered Raukumara tusked weta, Motuweta riparia. The Northland tusked weta lives in tree holes similar to tree weta. The Middle Island tusked weta, also called the Mercury Island
Mercury Islands
The Mercury Islands lie off the northeast coast of New Zealand's North Island. They are located off the coast of the Coromandel Peninsula, and northeast of the town of Whitianga....
tusked weta after the islands on which it lives, was discovered in 1970. It is a ground-dwelling weta, covering its shallow burrows with leaves. The Middle Island weta is the most endangered weta species and a Department of Conservation breeding programme is establishing new colonies on other islands of the Mercury Island group. The Raukumara was discovered in 1996, in the Raukumara Range
Raukumara Range
The Raukumara Range lies north of Gisborne, near East Cape in New Zealand's North Island. It forms part of the North Island's main mountain chain, which runs north-northeast from Wellington to East Cape, and is composed primarily of greywacke, argillites, siltstones and sandstones. The North...
near the Bay of Plenty
Bay of Plenty
The Bay of Plenty , often abbreviated to BOP, is a region in the North Island of New Zealand situated around the body of water of the same name...
. There are probably more species still to be identified.
Ground weta
Ground weta are classified in the genus HemiandrusHemiandrus
Hemiandrus is a genus of weta in the family Anostostomatidae. They are endemic to New Zealand and are known as ground wetas.-Species:* Hemiandrus bilobatus Ander, 1938* Hemiandrus fiordensis...
. There are about 40 species of ground weta in New Zealand and several very similar ones in Australia. There are also very like the Californian Cnemotettix—a similarity perhaps due to their very similar habits and habitat. Most of the Hemiandrus have not been described. They hide in burrows in the ground during the day and those that live in open ground (e.g., H. focalis) conceal the exit hole with a specially made perforated door. During the night ground weta hunt invertebrate prey and eat fruit.
Cave weta
The 60 species of cave weta have extra-long antennae, and may have long, slender legs and a passive demeanour. Although they have no hearing organs on their front legs like species of Hemideina and Deinacrida some (e.g., Talitropsis spp.) are very sensitive to ground vibrations sensed through pads on their feet. Specialised hairs on the cerciCercus
Cerci are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans. Cerci often serve as sensory organs, but they may also be used as weapons or copulation aids, or they may simply be vestigial structures.Typical cerci may appear to be...
and organs on the antennae are also sensitive to low frequency vibrations in the air. Cave weta may be active within the confines of their caves during the daytime, and those individuals close to cave entrances venture outside at night. But most species are forest dwellers and a few are to be found in the high alpine screes living among the broken rock that are covered with snow up to six months of the year. New Zealand species are classified in several genera in subfamily Macropathinae of family Rhaphidophoridae
Rhaphidophoridae
The orthopteran family Rhaphidophoridae includes the cave wetas, cave crickets, camelback crickets, camel crickets, spider crickets and sand treaders, of the suborder Ensifera; in some regions, such as Missouri and Virginia, these crickets are referred to as "Cricket Spiders"...
, and are very distant cousins of the other types of weta.
Conservation
Although the weta had native predators in the form of birds (especially the wekaWeka
The Weka or woodhen is a flightless bird species of the rail family. It is endemic to New Zealand, where four subspecies are recognized. Weka are sturdy brown birds, about the size of a chicken. As omnivores, they feed mainly on invertebrates and fruit...
and kiwi
Kiwi
Kiwi are flightless birds endemic to New Zealand, in the genus Apteryx and family Apterygidae.At around the size of a domestic chicken, kiwi are by far the smallest living ratites and lay the largest egg in relation to their body size of any species of bird in the world...
), reptiles and bats before the arrival of humans, introduced species such as cats, hedgehogs, rats (including kiore) and mustelids
Mustelidae
Mustelidae , commonly referred to as the weasel family, are a family of carnivorous mammals. Mustelids are diverse and the largest family in the order Carnivora, at least partly because in the past it has been a catch-all category for many early or poorly differentiated taxa...
have caused a sharp increase in the rate of predation. They are also vulnerable to habitat destruction caused by humans and modification of their habitat caused by introduced browsers. New Zealand’s Department of Conservation considers that 16 of the 70 species of weta are now at risk. Programmes to prevent extinctions have been implemented since the 1970s.
Some examples of especially endangered species are even tracked by radio beacons.
External links
- New Zealand Department of Conservation’s page on weta
- Weta from New Zealand
- Bug identification - Orthoptera
- Kiwi Conservation Club
- Sexual selection research on weta
- Wētā in Te Ara - the Encyclopedia of New Zealand
- A Key to the Tree and Ground Wetas of New Zealand in Tuatara: Volume 6, Issue 1, January 1956 - New Zealand Electronic Text Centre
- The Secret Life of Wetas - with insect expert George Gibbs
- Design and use of artificial refuges for monitoring adult tree weta