A University of Sydney research team reexamined Australian members of the stick insect genus Anchiale and discovered two new species. One produces unusual eggs with a distinctive lidlike structure. The researchers also restored a third species that had gone unrecognized for decades.

Their work shows that insects previously classified as just two species actually represent five separate species. Together, they occur from northern NSW along coastal Queensland and into tropical northern Australia.

Hidden Diversity Among Familiar Insects

Scientists reached these conclusions despite a large amount of existing information about Australian stick insects. More than 1000 citizen science observations have been submitted through iNaturalist and the Atlas of Living Australia, and the insects have also been studied scientifically for decades.

Even so, the researchers say much of Australia’s insect diversity remains undocumented.

Lead author Dr. Braxton Jones of the Aola Richards Sydney Insect Hub at the University of Sydney said the discoveries demonstrate how much scientists still have to learn about insect biodiversity.

“Taxonomy is often a bit like detective work. Even among some of Australia’s most photographed and frequently reported insects, we’re still finding species that have escaped scientific recognition,” said Dr. Jones, a Postdoctoral Research Associate in the Molecular Ecology, Evolution and Phylogenomics Laboratory.

Fun Facts About Stick Insects

• Many stick insects can reproduce without mating with a male. The process is known as parthenogenesis, in which a female produces eggs that develop into female-only offspring that are clones of herself.
• Some stick insects defend themselves by spraying chemicals at predators. The spray can irritate the eyes and mouth of an attacker.
• Australia’s longest stick insect measures around 62cm (the world record is 64cm). Australia has 130 known species, while 3609 species are known worldwide.
• Stick insects belong to a group called Phasmatodea, a name derived from an ancient Greek word meaning “phantom” or “ghost.” Their remarkable camouflage allows them to blend so effectively into vegetation that they can appear to vanish among leaves and branches.
• Some species can slowly change color to better match their surroundings. Their appearance can range from green to brown, and some can even resemble lichen as they blend into leaves, bark, and branches.
• Baby Extatosoma tiaratum stick insects use an especially unusual survival strategy. After hatching, the tiny nymphs have been observed emerging from ant nests while looking and behaving like ants. Their eggs can be carried into ant nests, where they remain dormant for months and receive protection from wasps. After hatching, the young insects use their ant-like color, shape, and behavior to move unnoticed toward the top of a eucalyptus tree.
• Some stick insects respond to threats by suddenly displaying brightly colored wings, which can startle predators. Certain species can also create a rustling noise with their wings, adding another defensive element to their wing morphology.
• If a predator catches a stick insect by the leg, some species can deliberately detach the limb and escape. This process is known as autotomy. Young stick insects can regenerate the missing leg during later molts, gradually restoring what was lost.

A Stick Insect Misidentified for Decades

One of the study’s biggest surprises involved a large stick insect that had long been familiar to both scientists and insect enthusiasts.

Researchers combined DNA analysis with museum specimens, field surveys, citizen science observations, and studies of insects raised in captivity. The evidence showed that the insect had been incorrectly identified for decades.

It is now recognized as a separate species called Anchiale robusta.

The findings are published in Austral Entomology.

The researchers also formally described Anchiale mabiensis, a new species found in Queensland’s critically endangered Mabi rainforest on the Atherton Tablelands.

Its eggs contain an unusual structural lid that has not previously been documented in any stick insect or its closest relatives.

Discovery Could Help Forestry and Agriculture

The revised classification may also have practical value.

One stick insect known for occasionally reaching plague-like population levels and stripping leaves from trees was found to represent more than one species. Distinguishing between those species could help researchers and land managers better understand and manage future impacts on forestry and agriculture.

The study also points to another possible new species from Cape York. Researchers believe it may be undescribed, but they need additional specimens before they can confirm its identity.

Dr. Jones said: “These findings demonstrate the importance of protecting threatened ecosystems and documenting Australia’s extraordinary biodiversity before we lose species without us having even discovered them.”

Funding for the research came from the Australian Biological Resources Study, through the National Taxonomy Research Grant of the Commonwealth Department of Climate Change, Energy, the Environment and Water, as well as a CSIRO postgraduate scholarship.