Two giant Australian stick insects turned out to be five, and one lays lidded eggs

Australia’s giant Anchiale stick insects, long treated as two species, are now recognized as five: Anchiale robusta, Anchiale mabiensis, Anchiale briareus, Anchiale albopunctata and Anchiale spinicollis. One of them, A. mabiensis, lays eggs with a structural lid not documented before in any stick insect.

The revision was led by Dr Braxton Jones at the University of Sydney and published in Austral Entomology 65(4), DOI 10.1111/aen.70096. Its title announces a revision of Australian Anchiale with two new species, and the arithmetic behind “two became five” takes a little unpacking, because the five are made up of different kinds of change.

The five Australian species, one by one

The University of Sydney’s release on the study, issued from the university’s insect research hub where Jones works as a postdoctoral research associate, describes A. robusta and A. mabiensis as the two newly described species. Coverage of the paper by Science News adds the physical contrast: A. mabiensis is small and fairly slender, with adult females about 11.5 centimetres long, while A. robusta is larger, with females reaching up to 16.2 centimetres.

The other three names come from the older literature. A. albopunctata has been restored to separate status on the basis of both anatomy and genetic evidence, after more than a century folded into A. briareus. Another outlet, Indian Defence Review, lists the five Australian members of the genus as albopunctata, briareus, mabiensis, robusta and spinicollis, and says the classification moved from two accepted species to five.

The German science outlet scinexx gives the fullest accounting of how the count gets there. By its reading, the name Anchiale austrotessulata, previously carried separately, is now assigned to A. briareus, and A. spinicollis remains as the fifth Australian species. The Wiley page for the paper itself returned an access error when read, so the fifth name rests on those two secondary accounts rather than on the paper’s text.

Mabi forest and the lidded egg

The lidded eggs belong to A. mabiensis, which is named for the Mabi forest of Queensland, the only place it has been found. The University of Sydney’s release says its eggs carry a structural lid unlike anything previously recorded in stick insects or their closest relatives, and Science News reports that the lid bears two to three rings, the first time such rings have been recorded in stick insects.

The detail matters because eggshell structure is a character they can compare across species, and a lid with no precedent in the group is a feature that tells species apart even when the adults look alike. Stick insect eggs are small, hard to find and rarely examined closely, which is part of why a structural lid went unrecorded for so long in a group that people have been naming since the nineteenth century.

The coastal species fill in the geography, and the range is wide. A. robusta occurs in coastal rainforest from Tully to Cooktown, according to Science News, and A. albopunctata in central Queensland. The study’s range runs through northern New South Wales, coastal Queensland and tropical northern Australia, per the ScienceDaily write-up of the university’s release.

A plague insect that turned out to be more than one species

One of the species at the centre of the revision is notorious. According to the University of Sydney, a stick insect known for forming plague-like outbreaks that can strip foliage from trees was found to consist of more than one species. A pest name that had covered a single species in the literature turns out to have covered several, which changes what a land manager means when reporting an outbreak.

Jones described the work as sleuthing. “Taxonomy is often a bit like detective work,” he said in the university’s account, and the clues here were anatomy, genetics and a reread of century-old naming decisions that had quietly merged one species into another.

His closing point was about conservation. In the release he said the findings demonstrate the importance of protecting threatened ecosystems and documenting Australia’s biodiversity before species are lost without having been discovered. A species known only from the Mabi forest is the kind of case he had in mind.

A possible sixth still waiting on specimens

The count is not necessarily final. The university’s release says the study also identified a likely additional undescribed species from Cape York, but that more specimens are needed before its identity can be confirmed. That animal is not among the five, and Science News places the whole group within a genus of 16 species living across most of the tropical Australasian regions, so the Australian five are a subset of a wider genus that still has gaps, and the Cape York animal is one of them.

For now the verified list is the one in the paper’s revision: two newly described species, one restored, one reassigned name and one long-standing species, with the Cape York animal waiting on more specimens, per the University of Sydney’s release as carried by ScienceDaily.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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