New stick insect species have been identified across eastern Australia, underscoring how much biodiversity remains uncharted even in well-studied habitats.
A team at the University of Sydney reexamined Australian members of the stick insect genus Anchiale and confirmed two species new to science, including one that lays distinctive eggs topped with a lidlike structure. The researchers also reinstated a third species that had gone unrecognized for decades.
According to the team, what had been grouped as two insects is now understood to comprise five distinct species distributed from northern New South Wales along the Queensland coast and into tropical northern Australia.
New stick insect species highlight hidden diversity
The conclusions emerged despite extensive prior knowledge of Australian stick insects. More than 1,000 citizen science records have been logged through iNaturalist and the Atlas of Living Australia, and the group has been the subject of formal study for decades.
Even so, the researchers say a substantial share of the continent’s insect diversity is still undocumented.
Lead author Dr. Braxton Jones of the Aola Richards Sydney Insect Hub at the University of Sydney said the results show how much remains to be learned about insect biodiversity. “Taxonomy is often a bit like detective work,” he said, noting that even heavily photographed and frequently reported insects can conceal undescribed species.
Fun Facts About Stick Insects
- Many stick insects can reproduce without males through parthenogenesis, producing female-only offspring.
- Some species defend themselves by spraying chemicals that irritate predators’ eyes and mouths.
- Australia’s longest stick insect is about 62 cm long. Australia has 130 known species, out of 3,609 described worldwide.
- Stick insects belong to Phasmatodea, from a Greek word meaning phantom or ghost, a nod to their camouflage.
- Certain species can slowly shift color to match surroundings, from greens to browns, and even resemble lichen.
- Newly hatched Extatosoma tiaratum nymphs mimic ants. Their eggs are carried into ant nests where they are protected, and the nymphs later move toward eucalyptus canopies while still resembling ants.
- Some species deter threats by flashing bright wings or creating rustling sounds. Others can shed a leg to escape and, if young, regrow it during later molts.
A long-misidentified giant gets a name
One of the study’s most notable findings concerned a large, familiar stick insect that had been misidentified for decades. By combining DNA evidence with museum collections, field surveys, citizen science observations, and studies of captive-reared insects, researchers determined it represents a separate species now recognized as Anchiale robusta.
The findings are published in Austral Entomology. The team also formally described Anchiale mabiensis, discovered in Queensland’s critically endangered Mabi rainforest on the Atherton Tablelands, and reported that its eggs possess a lidlike structure not previously documented in any stick insect or close relatives.
Implications for forestry and agriculture
The revised taxonomy could have practical benefits. An insect known to occasionally reach outbreak levels and defoliate trees was revealed to represent more than one species.
Differentiating those species could help researchers and land managers better anticipate and mitigate impacts on forestry and agriculture, echoing broader findings on how tree diversity shapes resilience in mixed-species forests.
The study also flags a possible additional species from Cape York. Researchers believe it may be undescribed but say more specimens are required to confirm its status.
Dr. Jones said the results underscore the urgency of protecting threatened ecosystems and cataloging Australia’s biodiversity before species disappear undocumented.
The research was funded by the Australian Biological Resources Study through the National Taxonomy Research Grant of the Commonwealth Department of Climate Change, Energy, the Environment and Water, along with a CSIRO postgraduate scholarship.