Overview
The Lord Howe Island Stick Insect (Dryococelus australis), famously dubbed the ‘tree lobster,’ is one of the heaviest, most iconic, and remarkably resilient flightless phasmids on Earth. Measuring up to 15 centimeters in length with a heavy, glossy jet-black to mahogany armored exoskeleton and thick, thorny legs, this extraordinary insect was once common throughout Australia’s remote Lord Howe Island. In 1918, a supply shipwreck introduced black rats to the island, which eradicated the entire wild population within two years.
Believed globally extinct for over eight decades, one of the most legendary chapters in modern conservation biology unfolded in 2001 when a mountaineering scientific expedition scaled Ball’s Pyramid—a near-vertical 560-meter sea stack 23 kilometers south of Lord Howe—and discovered a tiny relict colony of 24 individuals clinging to a single tea-tree bush. A daring rescue mission retrieved four specimens to launch an internationally celebrated captive-breeding program at Melbourne Zoo, saving the species from oblivion.
Biology and Physical Characteristics
Dryococelus australis is characterized by a heavy, wingless body encased in an exceptionally thick, armored cuticle. Adult males are distinguished by greatly enlarged, curved femoral spines on their rear legs, which they wield as powerful pinching weapons to grapple rival males and deter predators. Uniquely for stick insects, they exhibit nocturnal social bonding, with bonded pairs roosting together in tree hollows during daylight hours, the male wrapping his protective legs around the female.
Behavior and Ecology
Lord Howe Island stick insects are strictly nocturnal. By day, they conceal themselves deep inside the dark, hollow trunks of mature Melaleuca bushes or within subterranean basalt fissures where moisture is conserved. At dusk, they climb into the canopy to browse on fresh leaves. Females reproduce both sexually and through facultative parthenogenesis, depositing up to 300 large, beautifully textured, capsule-like eggs into moist soil that take nine months to hatch into bright emerald-green nymphs.
Conservation and Threats
Classified as Critically Endangered by the IUCN, the Lord Howe Island Stick Insect has become a global triumph of captive conservation. Thousands of individuals have been bred across Melbourne Zoo, San Diego Zoo, and Bristol Zoo. Following the historic, multi-million-dollar rodent eradication program on Lord Howe Island that successfully removed every rat and mouse by 2019, planned reintroductions of captive-bred tree lobsters are restoring this ancient insect to its ancestral home.
Interesting Factoid
The entire surviving population of Lord Howe Island stick insects hung by a thread on a single windswept tea-tree bush perched 65 meters above the ocean on the sheer cliffs of Ball’s Pyramid.