Lord Howe Island Stick Insect

Like its name suggests, Lord Howe Island Stick Insects (Dryococelus australis) is a species of stick insect that (used to) live on Lord Howe Island. That island is an irregularly shaped volcanic remnant (about ten kilometers long and between 0.3 and 2.0 kilometers wide). It lies in the Tasman Sea between Australia and New Zealand.

Lord Howe Island Stick Insects can measure up to 20 centimetres in length and weigh 25 grams, with males some 25% smaller than females. They are oblong in shape and have sturdy legs. The insects have no wings, but are able to run quickly.

The behaviour of this stick insect is highly unusual for an insect species: the females lay eggs while hanging from branches. The nymphs are first bright green and active during the day, but as they mature, they turn black and become nocturnal.

Reproduction can happen without the presence of males, a natural form of asexual reproduction called parthenogenesis. This has allowed the species to survive when they are low in numbers.

The Lord Howe Island Stick Insect used to be abundant on Lord Howe Island. In 1918, a ship ran aground on Lord Howe Island. In addition to its crew, the ship contained a horde of black rats (Rattus rattus) that quickly invaded the island. With no larger mammals to predate on the rats, their population exploded and they ate everything that moved. The stick insect was eventually classified as extinct in 1983, along with 12 other insect species and five bird species.

[Ball's Pyramid]

Yup, the species was thought to be extinct, until some freshly dead remains were found on Balls Pyramid during the 1960s. Ball's Pyramid is an erosional remnant of a shield volcano lying 20 kilometers south-east of Lord Howe Island in the Pacific Ocean. It is 562 meters high, while measuring only 1,100 metres in length and 300 metres across, making it the tallest volcanic stack in the world.

In February 2001, a survey of Balls Pyramid led to the discovery of a small population of Lord Howe Island Stick Insects on a precipitous terrace. Two adults and one nymph (all females) were located feeding on an endemic tea tree (Melaleuca howeana). All evidence indicated that the species was confined to this single small terrace. A second survey, in March 2002, located a total of 24 Lord Howe Island Stick Insects. Twelve individuals were in the same shrub as that occupied the previous year, and 12 were dispersed among five nearby, smaller shrubs.