Until now, the crown for Australia’s heaviest insect belonged to the giant burrowing cockroach, which weighs around 35 grams. However, high in the misty rainforests of northern Queensland, scientists recently stumbled upon a surprising supersized ‘twig’ that is way heavier.

Named Acrophylla alta, this rare stick insect can stretch up to 40 centimeters (about 15.75 inches) and weighs around 44 grams, just under the weight of a golf ball. The longest stick insects in the world can grow more than 50 centimeters, but even they are not as heavy as A. alta. 

“They weighed it and photographed the weighing of it, and it was 44 grams. We believe it’s the heaviest insect in Australia to date that’s been scientifically described,” Angus Emmot, one of the researchers and an adjunct professor at James Cook University, said. 

This new discovery doesn’t just add an impressive species to the record books, it highlights how much of our planet’s biodiversity is still hiding in plain sight, often in places humans rarely look.

Tracking the “supersized” sticky insect 

The hunt for A. alta began with a simple photograph. Wildlife expert Ross Coupland found an image of a stick insect on a social media platform (iNaturalist) that helps people share observations of plants, animals, and other organisms. Ross and Emmot instantly suspected it might be something scientists had never seen before. 

“The iNaturalist app/platform gives specific location details for observations. Therefore, I knew where they had been found. I knew they were a new species, given the morphology of the insects, so I went to look for them and subsequently found an individual that became the Holotype for the species,” Coupland told ZME Science.

They decided to investigate further. Their research led them to the insect’s home, the high-altitude rainforest canopy (900 meters above sea level) of the Atherton Tablelands, between Millaa Millaa and Mount Hypipamee, a region that’s both hard to reach and hard to search. Unless a storm, cyclone, or bird brings one down, spotting such insects was almost impossible. 

The two researchers spent several nights searching in the forest. Eventually, they spotted a large female clinging to a branch far overhead. Using a long stick, they carefully brought her down and transported her to Emmott’s home for closer study. They fed the insect and waited for her to lay eggs, because in the world of stick insects, eggs are as distinctive as fingerprints. Each species has its unique egg shape and texture, making them a reliable way to confirm identity.

“With stick insects, the eggs are very diagnostic, and so every different species has slightly different eggs,” Emmott said.

When the eggs were examined, the team knew for sure they had found a new species. Later, another female was discovered in a friend’s garden, and this one weighed 44 grams.

Currently, “the two females are lodged in the entomology collection at the Queensland Museum in Brisbane. We noticed that there is nothing unusual about their diet or behavior when compared to similar species of stick-insect.” Ross added.

The study authors suggest that this insect’s large body mass may be an adaptation to the cool, wet highland climate, helping it survive in conditions that smaller species might find challenging. However, so far, no male has been identified. Males in this family are usually smaller and look so different from females that they can easily be mistaken for a separate species or even a different genus. The only sure way to link them is to find a pair mating, then match their eggs.

You can only save what you know 

An interesting point to note here is that neither Ross nor Emmot is a professional scientist or entomologist. All of the work undertaken is done so out of their own passion and interest in the subject.

However, finding Acrophylla alta is more than just a curiosity for insect enthusiasts. It’s a reminder of how much remains undiscovered in the rainforest canopy. Many scientists suspect there could be countless species living high above the forest floor, completely unknown to us. 

For instance, according to an estimate, in Australia alone, as many as 70 percent of insect species are still undescribed. It is very crucial to find these organisms because there is no way we can protect a species if we don’t know it exists or where it lives. 

“Canopies are not well studied, so there’s a chance there are many more species in the canopy than we can even imagine,” Peter Valentine, an expert on environmental science, told the Australian Broadcasting Corporation. Peter wasn’t a part of the research.

Coupland and Emmot hope to soon locate a male A. alta, learn more about its population size, and understand its role in the ecosystem. However, they are also worried because it looks like time is not on their side. The rainforest ecosystems are under threat from invasive species, habitat loss, and climate change. Without long-term research and protection, there is a high chance that many species could vanish before they are found.

“The scary thing is we may be losing species before we even know they exist,” Emmot concluded.

The study is published in the journal Zootaxa.