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 1920, 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 24 individuals living on the small islet of Ball's Pyramid.