When a University of Sydney biology student lifted a rock under a huge banyan fig tree on Lord Howe Island, he could hardly believe what he saw.
It was a wingless wood-eating cockroach, unique to the World Heritage-listed island, and believed to be extinct. It was last seen more than 80 years ago.
"For the first 10 seconds or so, I thought, 'No, it can't be,'" honours student Maxim Adams said.
"We were doing a brief survey of Lord Howe basically to confirm its extinction there … and lo and behold the first rock we looked under there it was. It was really unbelievable."
Research takes unexpected turn
Mr Adams is a student under evolutionary biologist at the University of Sydney, Nathan Lo.
Professor Lo has been leading a research team examining the population distribution of the unique Lord Howe Island cockroach, Panesthia lata, across the Lord Howe Island archipelago, which lies off the mid-north coast of New South Wales.
The native cockroach was once widespread across the Lord Howe islands, but was thought to have become extinct on the main island after the arrival of rats in 1918.
Professor Lo said following the major and successful rodent eradication program on Lord Howe Island in 2019, they were examining the possibility of reintroducing the wood-feeding cockroach from the outer islands back to the main island.
Mr Adams and Department of Planning and Environment scientist Nicholas Carlile had gone to Lord Howe Island ahead of Professor Lo to make a start, when their research took a very unexpected turn.
"They were due to go out to Blackburn Island to start studying the cockroaches there, the weather was really bad, so they were forced to stay on Lord Howe Island," Professor Lo said.
"They went for a walk to the north end to look at some of the habitat where Panesthia lata cockroaches might have been happy to stay.
"The very first rock they looked under they found cockroaches, which is very strange, as entomologists have been looking on the island for many decades and haven't seen any at all."
The researchers ended up finding families of the cockroaches, all under one banyan tree.
A genetically distinct species
Professor Lo said DNA work had confirmed the importance of the discovery.
"We sequenced their DNA and compared it with the DNA of cockroaches from Blackburn and so far, they seem different. The same species probably, but they seem to be a distinct population," he said.
"It does seem this little population in the north end of the island has hung on over many decades. It's exciting, they might be able to re-establish across the island over time."
Lord Howe Island board chair Atticus Fleming said it was an exciting find.
"Lord Howe Island really is a spectacular place. It's older than the Galápagos Islands and is home to 1,600 native invertebrate species, half of which are found nowhere else in the world," he said.
"These cockroaches are almost like our very own version of Darwin's finches, separated on little islands over thousands or millions of years developing their own unique genetics."
'Charismatic' cockroach ecologically important
Professor Lo said the native wood-eating cockroaches played an important environmental role.
"They are incredibly important nutrient recyclers, ecosystem engineers and as a food source for other species," Professor Lo said.
He said the species also deserved a better rap than "common street roaches".
"It doesn't smell, it doesn't run really quickly, it's not scary. It's actually quite charismatic, you can hold it in your hand," he said.
"It just hangs out in the forest. It does not go into people's houses. It's just out in the forest recycling the wood and leaf litter, to keep the forest healthy.
"That's why we are interested in it, because it was so abundant before the rats wiped it out. We figure it was probably playing a pretty important ecological role on the island, also acting as food for a number of the bird and reptile species out there."
Professor Lo said there was still much to learn.
"This species lives for a long time, about seven or eight years, but doesn't breed anywhere as quickly as your common street roaches," he said.
"We are hoping to study their habitat, behaviours and genetics to learn more about how they managed to survive."
