World's rarest insect returns after a century of absence

When the SS Makambo ran aground on Lord Howe Island in 1918, only one person was reported to have drowned. In the aftermath, however, a slow-moving disaster was set in motion that nearly destroyed a unique, flightless stick insect. 

Black rats escaped onto the Island from the grounded vessel, found no natural predators, and quickly attacked local fauna.

Several species vanished in a blink, including the now-famous Lord Howe Island stick insect (Dryococelus australis).

Reckoning with unseen consequences

Scientists thought the Lord Howe Island stick insect was wiped out by around 1920. No new sightings or specimens of this insect species turned up for decades.

After countless searches, the creature earned a grim reputation as just another island species lost to invasive rats. 

In 2001, two determined researchers, Dr. David Priddel and Dr. Nicholas Carlile from the NSW Government’s Office of Environment and Heritage, decided to settle the mystery once and for all.

They joined an expedition to Ball’s Pyramid, a tall sea stack about 14 miles from Lord Howe Island, where a few climbers had reported stumbling on suspicious insect remains.

Hidden haven of Lord Howe Island stick insects

Cautious climbs up the windy cliffs at Ball’s Pyramid revealed a stark, barren rock. Despite that, a cluster of tea tree bushes held an astonishing secret.

A tiny population of living Lord Howe Island stick insects had somehow persisted there. 

“We’d get requests from people saying they were going to find this stick insect,” says Carlile, “but then you’d look at the list of people and there wouldn’t be an entomologist on there!”

Not only did a few insects survive, but they also managed to multiply within a cramped, precarious habitat.

Size and surprises

Known as “tree lobsters,” these insects grow up to 5 inches (12.7 cm) in length, weigh up to 0.9 ounces (25 grams), and have a hard exoskeleton.

Reports from early island residents suggest they were so plentiful that some people used them as fishing bait. 

Researchers believe the survivors on Ball’s Pyramid likely benefited from the rugged environment, which had no rats.

Another factor that may have helped is a special trick called parthenogenesis, which lets female insects lay fertile eggs even without a mate. 

An October 2017 study in Current Biology confirmed the Ball’s Pyramid population is genetically the same species once found on Lord Howe Island.

A fragile comeback

Bringing the stick insect home involved careful planning. In 2003, biologists took two of the insects – nicknamed Adam and Eve – to Melbourne Zoo and launched a breeding program. 

Early attempts ran into problems, but patience paid off. The insects multiplied, and zoos worldwide – San Diego Zoo and Bristol Zoo among them – took part in safeguarding these large, slow-moving invertebrates. 

Researchers wanted to see if Lord Howe Island itself could ever host them again. That possibility hinged on ridding the island of rats and mice, a project that gained momentum in 2019.

Killing rats to save Lord Howe Island stick insects

Conservation teams used aerial and ground applications of rodent baits to get rid of every rat and mouse.

Locals worried about the impact on other animals would have on the stick insects, but the operation’s leaders stressed that rodents were the real threat. 

According to global studies, rats are a top cause of bird and insect extinctions on islands.

By late 2019, officials declared Lord Howe Island free of these invasive rodents. However, a stray rat was spotted in April 2021, which led to a fast response. 

The final check showed that a few persistent rats had descended from a tiny remnant that avoided the initial eradication. Authorities adjusted their monitoring methods, and the island’s rodent-free status is still a goal.

Looking forward

Today, thousands of stick insects have been bred in captivity and stand ready for eventual release. Researchers aim to make sure the island’s vegetation has recovered and that any lurking rodent threat is completely gone. The insects’ dependence on safe hideouts is clear. 

They once congregated by the dozens in tree hollows, a behavior that left them vulnerable to hungry rats. Without predators, the insects will have a better shot at thriving in their original home, completing a circle that has been nearly a century in the making.

Lord Howe Island stick insect conservation

Biologists agree that this return is more than an ecological curiosity. It reflects the importance of eradicating invasive species to protect fragile island habitats.

The Lord Howe Island stick insect’s recovery also highlights how a few survivors can carry a species forward. 

Although some questions linger about their survival on Ball’s Pyramid, one thing is certain: they’ve gone from presumed extinct to promising comeback.

Conservationists can’t wait for the day when these long-legged insects reclaim the trees and hollows of Lord Howe Island, undisturbed by rats and free to walk the night once more.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.