Dryococelus australis

Dryococelus australis
Conservation status
Critically Endangered (IUCN 3.1) [1]
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Phasmatodea
Family:	Phasmatidae
Genus:	Dryococelus
Species:	D. australis
Binomial name
Dryococelus australis (Montrouzier, 1885)

Dryococelus australis, commonly known as the Lord Howe Island stick insect or tree lobster,^[2] 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.

Anatomy and behaviour

Adult Lord Howe Island stick insects can measure up to 15 centimetres (5.9 in) in length and weigh 25 grams (0.88 oz) with females bigger than males. 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.

History and conservation

The stick insects were once very common on Lord Howe Island, 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 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 (1,844 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 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. 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.

See also

• Threatened fauna of Australia
• Island gigantism

References

1. ^ "Dryococelus australis". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. 2002. http://www.iucnredlist.org/apps/redlist/details/6852. Retrieved 3 April 2010. 
2. ^ Stohr, Stephanie. "Tree lobster came from ancient sunken island". Cosmos Magazine. 

• 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, 15 July 2006
• ABC news report, with video
• Phylogenetic study on Dryococelus australis