Scientists discover a stick insect as heavy as a golf ball

A new stick insect from the Wet Tropics of Far North Queensland has stepped into the spotlight with unusual heft and length. The female measures about 15.75 inches and weighs roughly 1.55 ounces.

Scientists formally described the species, named Acrophylla alta, and noted that its distinctive eggs helped clinch the identification. Their peer reviewed paper sets out the traits that separate it from close relatives.

Acrophylla alta stands out

The field work and identification included Angus Emmott of James Cook University. His team focused on features that hold up under close examination, not quick impressions.

Stick insects belong to the order of phasmid insects, which are known for camouflage that mimics twigs and branches.

Many are long, but length alone does not equal mass, and this species tips the scales in a way others do not.

Acrophylla alta has limbs and body segments that flatten and align with bark and stems. That shape helps it avoid predators that hunt by sight, especially birds.

Where it hides

The species lives in high elevation rainforest, tucked in the upper tree layer that researchers call the canopy, the sunlit zone formed by interlocking treetops. That perch keeps the insect out of reach and out of view during most surveys.

“It’s restricted to a small area of high-altitude rainforest, and 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. From what we know to date, this is Australia’s heaviest insect,” said Emmott.

Field teams face steep slopes, slick ground, and thick foliage, so their windows for observing canopy insects are short.

Night work with headlamps helps, yet the odds of spotting a single well camouflaged individual remain low.

To ensure other scientists can study the species, two specimens entered the Queensland Museum collection. That move supports future taxonomic checks and comparisons.

How scientists knew it was new

“Every species of stick insect has their own distinct egg style,” said Emmott. Acrophylla alta stood out because of its eggs, which carry shapes and surface patterns that differ from related species. 

Taxonomists rely on multiple traits, but eggs are especially useful in this group because they remain intact and identifiable even when adults are scarce.

The formal description includes a key that lets researchers separate this insect from others in its genus.

The authors also recorded habitat features and food plants that help narrow where to look next. That guidance saves time and keeps field effort focused in the right places.

Size helps Acrophylla alta survive

“Their body mass likely helps them survive the colder conditions, and that’s why they’ve developed into this large insect over millions of years,” said Emmott. The comment fits what biologists expect in cool upland settings.

Bigger bodies lose heat more slowly than small ones because they have less surface area relative to volume.

Insects do not make their own body heat like mammals, so carrying extra mass can buffer temperature swings at night.

Extra mass is not free, since heavy bodies need more food and make flight harder. The balance of benefits and costs likely pushed this species toward a size that works in its home range.

What its discovery means for science

New species help fill gaps in family trees and distribution maps. Each addition sharpens our sense of how insects diversified across climate zones and elevations.

Acrophylla alta also updates the upper limit for insect mass in Australia, a value used in comparisons across regions. That benchmark matters when scientists study how body size tracks with temperature and moisture.

The museum specimens give future teams a reference point for DNA work and morphometrics. With verified material on hand, researchers can test new questions without waiting for a rare field encounter.

Why this finding matters

Species that occupy small, high elevation pockets can be vulnerable to shifts in temperature and humidity. If cool nights warm up or dry spells lengthen, the conditions that favor large body mass could change.

Forests that hold canopy specialists tend to host many other narrow range species. Protecting those patches, even if they look small on a map, safeguards a lot of hidden diversity at once.

Good data drives good protection plans, but you first need to know what lives where. This discovery underscores how much biodiversity remains tucked out of sight.

Next steps for Acrophylla alta

Researchers will try to map the full range of Acrophylla alta to confirm whether it is limited to a few mountaintops. That will inform how to rank its conservation priority.

The team will also work to document its full life cycle, including development times and seasonal patterns. Captive rearing from eggs could answer several of those questions without heavy field disturbance.

Finding males can clarify differences between sexes and refine identification keys. That information helps non specialists make accurate calls in the field.

Field biology often means long nights, wet boots, and more misses than hits. Patience counts, because one clean observation can unlock a series of findings.

When a species turns out to be both large and rare in sightings, it can challenge assumptions about how we search. Acrophylla alta shows that absence of records does not equal absence of life in the canopy.

The study is published in Zootaxa.

Image credits: David Midgley.

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