A newly discovered stick insect measuring 40 centimetres in length and weighing slightly less than a golf ball may be the heaviest insect in Australia, scientists have said. The species, named Acrophylla alta, was found in the high altitudes of the Atherton Tablelands in north Queensland.
The discovery, documented in the journal Zootaxa, began with a social media post. Professor Angus Emmott of James Cook University said his co-author Ross Coupland was sent a photo of a stick insect and immediately suspected it might be new. After many nights of searching, the pair found a large female between Millaa Millaa and Mount Hypipamee, so high in the trees that they had to use a long stick to bring it down.
Professor Emmott believes the species had not been discovered earlier because its habitat is difficult 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,” he said. The cool, wet environment may also explain the insect’s large size, as greater body mass helps survive the cold conditions.
Finding a male has proven challenging. Male stick insects are significantly smaller and visually distinct from females, so much so that in other cases pairs have been described as different species or even genera. Professor Emmott noted that finding a male copulating with a female is essential to confirm the pairing and collect eggs for study.
Queensland Museum entomologist Nicole Gunter said the discovery fills a gap in knowledge about Australia’s biodiversity. “Australia is home to an immense amount of biodiversity that has yet to be classified and given a scientific name,” she said, estimating that up to 70% of Australian insect species are currently undescribed. She emphasised that recognising this species is vital for conservation efforts.
So far, the stick insect has only been recorded in a small number of forest localities in the wet tropics region of Queensland. Future surveys will help improve understanding of its distribution and any potential threats it faces.
