Stick insect as large as a branch and as heavy as a golf ball has been discovered in Australia

A giant walking stick insect has stepped out of the treetops in north Queensland, and it is creating a stir for its size. It reaches about 15.75 inches (40 centimeters) in length, and weighs around 1.6 ounces (45 gra,s).

Scientists have now given it a formal name, Acrophylla alta. The species was described in the taxonomic journal Zootaxa, in a peer-reviewed study that detailed its features and habitat.

Why Acrophylla alta stands out

The study’s co-author Angus Emmott of James Cook University (JCU) led fieldwork that brought the insect out of obscurity. His team focuses on large, camouflaged insects that are easy to overlook yet important to local ecosystems.

Stick insects belong to the Phasmatodea, an order of insects known for their twig-like bodies and leaf-shaped limbs. This group relies on camouflage rather than speed or stingers to avoid predators.

Acrophylla alta is notable for mass rather than sheer length. It has the same weight as a typical golf ball. That difference matters because weight influences energy use, egg production, and how an animal copes with cool nights.

Finding Acrophylla alta

Researchers followed a tipoff from a social media photo and searched misty uplands for nights on end.

Their work paid off when they found a female at an altitude of roughly 2,950 feet (900 meters) in the ancient rainforest of the Wet Tropics.

“We looked at its eggs after it laid some eggs and we were absolutely certain it was a new species,” said Emmott. They confirmed the identity by studying the eggs, which carry species-specific patterns and structures. 

“With stick insects, the eggs are very diagnostic, and so every different species has slightly different eggs,” said Emmott. Egg shape and texture often separate close relatives when color and size overlap. 

Two more females have been documented since the first find. The male remains uncollected and is expected to be smaller and slimmer.

This species lives in the canopy, the upper layer of forest where leaves form a dense roof. That height keeps it hidden from people and protects it from many predators on the ground.

The habitat is cool and wet compared with lower slopes. Researchers say its large body mass may reflect those conditions.

“I think you could spend a long time looking for one and not find one,” said Emmott. Finding any individual is hard in this habitat because the insects rarely come down.

Why size could help stick insects

Biologists continue to test how insect body sizes relate to ambient temperature. Some groups grow larger in cooler places, while others show the reverse pattern, as an open access analysis on bumblebees explains.

Mass can reduce heat loss by lowering the surface-to-volume ratio. Heavier bodies also store more energy, which can be significant during long, rainy stretches when food is scarce.

High elevations often mean slower growth because temperatures limit feeding and metabolism. Larger size in adults may reflect selection for individuals that endure those constraints.

No one has described the male yet, which limits what scientists can say about the full life cycle. The team expects the male to differ in color and shape, which is common in stick insects.

Distribution is still a big question, too. Known sites cluster in the highlands of the Wet Tropics, but the true range may be broader or patchier, in pockets of suitable forest.

Australia’s insect community

Australia hosts many endemic species, meaning they live in that country or region and nowhere else. That uniqueness makes documentation urgent when habitats face invasive species and climate pressures.

The rainforest canopy is still under-sampled because it is tough to reach and survey. Ropes, cranes, and drones help, but time in the treetops remains limited for most field teams.

New finds like Acrophylla alta highlight hidden diversity in a country that is already famous for unusual fauna. Each species carries its own role in pollination, nutrient cycling, and food webs.

Acrophylla alta reshapes field priorities

This new stick insect, Acrophylla alta, shows the value of looking up, not just along trails and streams. Canopy searches can reveal animals that decades of ground surveys missed.

Focusing on life history, from egg to adult, can sharpen identification in groups that are hard to tell apart. The egg-centric approach used here is a practical example of that method.

Local communities and hikers can help by sharing clear photos and locations with researchers. Good records lead to better maps, smarter surveys, and faster protection when needed.

The study is published in Zootaxa.

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