Dryococelus australis
Encyclopedia
Dryococelus australis, commonly known as the Lord Howe Island stick insect or tree lobster, is a species
of stick insect which lives on the Lord Howe Island Group. It was thought to be extinct by 1930, only to be rediscovered in 2001 (this phenomenon is known as the Lazarus effect
). It is extinct in its largest habitat, Lord Howe Island
, and has been called "the rarest insect in the world", as the rediscovered population consisted of fewer than 30 individuals living on the small islet of Ball's Pyramid
.
s bigger than male
s. They are oblong in shape and have sturdy legs. Males have thicker thighs than females. Unlike most phasmids they have no wings, but are able to run quickly.
The behaviour of this stick insect is highly unusual for an insect species. The males and females form a bond; the males follow the females and their activities depend on what the female is doing.
The females lay eggs while hanging from branches. Hatching can happen up to nine months later. The nymphs
are first bright green and active during the day, but as they mature they turn black and become nocturnal.
, where they were used as bait in fishing. They became extinct there soon after black rats were introduced to the island in 1918 when the supply ship S.S. Makambo
ran aground. The last one was seen on the island in 1920, and after that the species was thought to be extinct.
In the 1960s a team of climbers visited Ball's Pyramid
, a rocky sea stack 23 kilometres (14.3 mi) south-east of Lord Howe Island
. Ball's Pyramid is the world's tallest sea stack. The islet is treeless and extremely steep, with a peak 562 metres (1,843.8 ft) from the sea surface. The climbers discovered a dead Lord Howe Island stick insect. During subsequent years, a few more dead insects were discovered, but expeditions to find live specimens failed.
In 2001, a team of entomologists and conservationist
s landed on Ball's Pyramid to chart its flora
and fauna
. To their surprise they rediscovered a population
of stick insects living under a single Melaleuca
shrub. The population was extremely small, only 20–30 individuals.
In 2003 a research team from New South Wales
National Parks and Wildlife Service returned to Ball's Pyramid
and collected two breeding pair
s, one pair going to a private breeder in Sydney
and the other to Melbourne Zoo
. After severe initial difficulties they successfully bred in captivity. The ultimate goal is to produce a large population for re-introduction to Lord Howe Island
if the project to eradicate the invasive
rats is successful. In 2006 the captive population was about 50 individuals and thousands of eggs waiting to hatch. As of 2008 the population had grown to about 450 insects and 20 had been returned to a special habitat on Lord Howe Island.
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...
of stick insect which lives on the Lord Howe Island Group. It was thought to be extinct by 1930, only to be rediscovered in 2001 (this phenomenon is known as the Lazarus effect
Lazarus taxon
In paleontology, a Lazarus taxon is a taxon that disappears from one or more periods of the fossil record, only to appear again later. The term refers to the account in the Gospel of John, in which Jesus raised Lazarus from the dead...
). It is extinct in its largest habitat, Lord Howe Island
Lord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
, and has been called "the rarest insect in the world", as the rediscovered population consisted of fewer than 30 individuals living on the small islet of Ball's Pyramid
Ball's Pyramid
Ball's Pyramid is an erosional remnant of a shield volcano and caldera that formed about 7 million years ago. Ball's Pyramid is southeast of Lord Howe Island in the Pacific Ocean. It is high, while measuring only in length and across, making it the tallest volcanic stack in the world...
.
Anatomy and behaviour
Adult Lord Howe Island stick insects can measure up to 15 centimetres (5.9 in) in length and weigh 25 gram (0.881849052627799 oz) with femaleFemale
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
s bigger than male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
s. They are oblong in shape and have sturdy legs. Males have thicker thighs than females. Unlike most phasmids they have no wings, but are able to run quickly.
The behaviour of this stick insect is highly unusual for an insect species. The males and females form a bond; the males follow the females and their activities depend on what the female is doing.
The females lay eggs while hanging from branches. Hatching can happen up to nine months later. The nymphs
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
are first bright green and active during the day, but as they mature they turn black and become nocturnal.
History and conservation
The stick insects were once very common on Lord Howe IslandLord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
, where they were used as bait in fishing. They became extinct there soon after black rats were introduced to the island in 1918 when the supply ship S.S. Makambo
SS Makambo
The SS Makambo was a steamship first owned by Burns Philp & Co. Ltd. She was built in Port Glasgow and named after an island in the Solomon Islands. She carried both passengers and cargo and was principally used on routes between eastern Australia and islands in Melanesia and the Tasman Sea...
ran aground. The last one was seen on the island in 1920, and after that the species was thought to be extinct.
In the 1960s a team of climbers visited Ball's Pyramid
Ball's Pyramid
Ball's Pyramid is an erosional remnant of a shield volcano and caldera that formed about 7 million years ago. Ball's Pyramid is southeast of Lord Howe Island in the Pacific Ocean. It is high, while measuring only in length and across, making it the tallest volcanic stack in the world...
, a rocky sea stack 23 kilometres (14.3 mi) south-east of Lord Howe Island
Lord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
. Ball's Pyramid is the world's tallest sea stack. The islet is treeless and extremely steep, with a peak 562 metres (1,843.8 ft) from the sea surface. The climbers discovered a dead Lord Howe Island stick insect. During subsequent years, a few more dead insects were discovered, but expeditions to find live specimens failed.
In 2001, a team of entomologists and conservationist
Conservationist
Conservationists are proponents or advocates of conservation. They advocate for the protection of all the species in an ecosystem with a strong focus on the natural environment...
s landed on Ball's Pyramid to chart its flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...
and fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
. To their surprise they rediscovered a population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
of stick insects living under a single Melaleuca
Melaleuca howeana
Melaleuca howeana is a shrub or bush to 3 m tall in the myrtle family. It grows at the Lord Howe Island group. Common in exposed areas, on cliffs and ridges, occasionally forming pure stands....
shrub. The population was extremely small, only 20–30 individuals.
In 2003 a research team from New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
National Parks and Wildlife Service returned to Ball's Pyramid
Ball's Pyramid
Ball's Pyramid is an erosional remnant of a shield volcano and caldera that formed about 7 million years ago. Ball's Pyramid is southeast of Lord Howe Island in the Pacific Ocean. It is high, while measuring only in length and across, making it the tallest volcanic stack in the world...
and collected two breeding pair
Breeding pair
Breeding pair is a pair of animals which cooperate over time to produce offspring with some form of a bond between the individuals. For example, many birds mate for a breeding season or sometimes for life. They may share some or all of the tasks involved: building a nest, incubating the eggs and...
s, one pair going to a private breeder in Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...
and the other to Melbourne Zoo
Melbourne Zoo
The Royal Melbourne Zoological Gardens, commonly known as the Melbourne Zoo, contains more than 320 animal species from Australia and around the world. The zoo is north of the centre of Melbourne. It is accessible via Royal Park station on the Upfield railway line, and is also accessible via tram...
. After severe initial difficulties they successfully bred in captivity. The ultimate goal is to produce a large population for re-introduction to Lord Howe Island
Lord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
if the project to eradicate the invasive
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
rats is successful. In 2006 the captive population was about 50 individuals and thousands of eggs waiting to hatch. As of 2008 the population had grown to about 450 insects and 20 had been returned to a special habitat on Lord Howe Island.