A newly discovered stick insect which weighs slightly less than a golf ball may be the heaviest insect in Australia, scientists say.
The 40cm-long new species, named Acrophylla alta, was found in the high altitudes of the Atherton tablelands in north Queensland – and scientists said the habitat could be part of the reason for its large size.
A peer-reviewed study documenting the discovery, published in Zootaxa journal, noted the stick insect was likely heavier than the giant burrowing cockroach, which is endemic to Queensland and is at present the heaviest insect in Australia.
James Cook University researcher Prof Angus Emmott said a social media post helped with the discovery.
Sign up: AU Breaking News email
Emmott said his co-author on the study, Ross Coupland, was sent a photo of a stick insect and “immediately thought that it might be something new”.
After many nights of searching, Emmott and Coupland found a big female between Millaa Millaa and Mount Hypipamee. The insect was so high up that they had to use a long stick to get it down.
As soon as Coupland saw the female up close, he was positive it was a new species of stick insect. The pair took it to Emmott’s Atherton tablelands home for further study.
They kept the female in a cage, fed it and then collected its eggs.
“With stick insects, the eggs are very diagnostic, and so every different species has slightly different eggs,” Emmott said.
Emmott said he believed the species had not been discovered earlier as its habitat was too hard to access.
“It lives high in the canopy. So, unless you get a cyclone or a bird bringing one down, very few people get to see them,” Emmott said in a statement.
But the habitat could also explain why the stick insect is larger, he said, saying the body mass could help them survive the cold conditions in the “cool, wet environment where they live”.
The next step in identifying more about the species is finding a male, which is proving difficult, and not just because they are as thin as a stick.
Male stick insects tend to be significantly smaller and visually distinct from females, so much so that in other cases pairs have been described not only as different species, but from a different genus altogether.
“You really need to find the male copulating with the female,” Emmott said.
“You know what it is then, and you collect the eggs and you can actually ascertain that they’re one of the same thing.”
Queensland Museum’s entomology expert Nicole Gunter said the discovery filled a gap in knowledge about Australia’s biodiversity.
It also highlighted that there was much to learn about some of Australia’s largest insect species, she said. “Australia is home to an immense amount of biodiversity that has yet to be classified and given a scientific name.”
She estimated up to 70% of Australian insect species are currently undescribed.
“Recognising this species as distinct is also important for its conservation. We can’t conserve a species if we don’t know it exists or where it occurs.”
She said this species of stick insect had so far only been recorded in a small number of forest localities in the wet tropics region of Queensland.
Future surveys could help improve the scientific understanding of the insect’s distribution and any potential threats the species faces.
– with AAP
