Dryococelus australis
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| Lord Howe Island stick insect | ||||||||||||||
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| Dryococelus australis (Montrouzier, 1885) |
The Lord Howe Island stick insect (Dryococelus australis) 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.
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[edit] Anatomy and behaviour
Adult Lord Howe Island stick insects can measure up to 15 cm in length and weigh 25 g with females bigger than males, and for their size are sometimes called land lobsters or walking sausages. They are oblong in shape and have sturdy legs. Males have unusually thick thighs. Unlike most phasmids they have no wings, but are able to run quickly.
The behavior of this stick insect is highly unusual for an insect species. The males and females form some kind of a bond. The males follow the females and their activities depend on what the female is doing. During the night the couple sleeps together with three of the male's legs wrapped around the female.
The females lay eggs while hanging from branches. The males wait below to bury the eggs into soil. 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.
[edit] History and conservation
The stick insects were once very common on Lord Howe Island, where they were once used as bait in fishing. They became extinct there soon after Black rats were introduced to the island in 1918 when the supply ship 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 km south-east of Lord Howe Island. Ball’s Pyramid is the world's tallest and most isolated sea stack. The islet is treeless and extremely steep, with a peak 562 m 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 conservationists 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 pairs, 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. As of 2006, the captive population is about 50 individuals and thousands of eggs waiting to hatch.
[edit] See also
[edit] References
- ANZECC Endangered Fauna Network (2002). 'Dryococelus australis'. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is critically endangered
- The Lord Howe Island Phasmid: an extinct species reborn by David Priddel, at the Foundation for National Parks & Wildlife
- Preparing Lord Howe for the reintroduction of the Phasmid by Carmen Welss, at the Foundation for National Parks & Wildlife
- Sticks and stones article, Sydney Morning Herald, 18 October 2003 (with picture)
- Giant stick insect rediscovered, science news 14 February 2001 at the Australian Broadcasting Corporation
- New Scientist, July 15, 2006
