The project was led by Dr Braxton Jones, a Postdoctoral Research Associate in the Molecular Ecology, Evolution and Phylogenomics Laboratory and a member of the Aola Richards Sydney Insect Hub at the University of Sydney. Jones describes taxonomic work of this kind as a form of detective investigation, in which scattered clues gathered from museum drawers, field surveys, captive colonies and online photograph databases must be pieced together into a coherent evolutionary story. Even among some of Australia’s most photographed and most frequently reported insects, the team found species that had escaped formal scientific recognition. The fact that thousands of people have posted images of these very insects on citizen science platforms, without anyone realising that several different species were being conflated, underscores how easily biodiversity can slip past even an attentive public.

The methodological foundation of the revision was deliberately broad. Jones and colleagues combined DNA analysis with the examination of museum specimens, targeted field surveys, citizen science records submitted through iNaturalist and the Atlas of Living Australia, and studies of captive populations kept by insect enthusiasts. More than 1000 citizen science observations of stick insects were available to the researchers, a remarkable evidence base for any invertebrate group. By integrating genetic data with subtle differences in body shape, egg morphology and geographic distribution, the team was able to demonstrate that the two recognised Australian Anchiale species were in fact masks covering five separate evolutionary lineages. This kind of integrative taxonomy, in which no single line of evidence is treated as decisive on its own, has become the standard for resolving species boundaries in groups where external appearances are misleadingly similar.

One of the biggest surprises involved a large stick insect that has been familiar to scientists and amateur insect keepers for generations. After combining every available source of evidence, the researchers concluded that this well-known animal had been misidentified for decades. It is now formally described as Anchiale robusta, an entirely new species that had been living under the name of a relative. For a creature so large and so conspicuous, found in backyards and bushland within easy reach of entomologists, the discovery is a vivid illustration of the limits of traditional species inventories. Museum collections, the study suggests, are not static archives of what is known but reservoirs of unrecognised diversity waiting for the right analytical tools and the right questions.

The second new species, Anchiale mabiensis, carries an ecological warning with its name. It was discovered in Queensland’s Mabi rainforest on the Atherton Tablelands, an ecosystem officially listed as critically endangered and now reduced to small, fragmented patches. Perhaps the most remarkable feature of this insect is its eggs, which contain a structural lid unlike anything previously recorded in stick insects or their closest relatives. Egg morphology is a crucial diagnostic character in phasmid taxonomy, because eggs are often more distinctive than the insects themselves, and the lidded eggs of A. mabiensis represent a genuinely novel structure within the broader radiation of these insects. That such an anatomical novelty was found in a threatened habitat adds urgency to its documentation, since the species’ future is tied directly to the survival of the forest fragments it inhabits.

The revision also has immediate practical consequences beyond the cataloguing of new life. One of the species previously lumped under a single name is notorious for forming plague-like population outbreaks, sometimes in numbers large enough to strip foliage from trees, creating problems for forestry and agricultural operations. The study found that this outbreak-forming insect actually consists of more than one species, which means that past records of its biology, distribution and pest potential may have blended together the traits of several distinct organisms. Untangling those species relationships, the researchers argue, will be essential for improving future management of the impacts these insects have on commercial plantations and crops. Understanding which species is capable of what kind of outbreak, and where each one lives, is the first step toward targeted rather than blanket control measures.

The detective work is not even complete. The study identified a likely additional, still undescribed species from Cape York on the far northern tip of the continent, but the team concluded that more specimens are needed before its identity can be confirmed with confidence. This lingering question mark is itself telling. A single regional revision of one genus has yielded two new species, one reinstated species and one candidate species, suggesting that the true diversity of Australian Phasmatodea may be substantially underestimated. With roughly 130 described stick insect species in Australia and about 3609 worldwide, the country’s phasmid fauna is clearly only beginning to be mapped.

The broader message the researchers draw from the work is a cautionary one about the pace of discovery versus the pace of environmental change. Despite decades of scientific study and a citizen science infrastructure that now captures well over a thousand observations of these insects, Australia is, in their assessment, still only scratching the surface of its insect diversity. Jones emphasises that findings of this kind demonstrate the importance of protecting threatened ecosystems and documenting the country’s extraordinary biodiversity before species are lost without ever having been discovered. An insect like Anchiale mabiensis, confined to a critically endangered rainforest type, is a concrete example of a species that could have vanished entirely before anyone knew it existed.

For a group of animals built to be invisible, stick insects have a remarkable ability to surprise the people who study them. Their name-bearing order, Phasmatodea, derives from an ancient Greek word meaning phantom or ghost, a reference to camouflage so effective that the insects seem to vanish among the vegetation. Many species can reproduce without mating, females producing female-only clones through parthenogenesis; some can spray irritating chemicals at predators, flash brightly coloured wings, rustle their wings to startle attackers, or deliberately shed a grabbed leg and regrow it over successive moults. Australia’s longest stick insect reaches around 62 centimetres, just short of the world record of 64 centimetres. Baby Extatosoma tiaratum nymphs even hatch in association with ant nests, mimicking the ants’ appearance and behaviour long enough to scramble unnoticed into the treetops. The newly recognised Anchiale species now add a further layer of wonder to this catalogue of oddities, and they serve as a reminder that even the phantoms of the backyard have stories left to tell.

Subject of Research: Taxonomic revision of Australian Anchiale stick insects revealing two new species and a reinstated species

Article Title: New large stick insect species revealed in Australia’s backyards and rainforests

Article References: New large stick insect species revealed in Australia’s backyards and rainforests. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: stick insects, Anchiale, taxonomy, Australia, new species, Austral Entomology, Mabi rainforest, citizen science, entomology, biodiversity, Phasmatodea, University of Sydney

The research, published in The Science of Nature, took a two-pronged approach that combined living feeding trials with laboratory simulations of avian digestion. Led by Judith Burack, Eberhard Haase, Stanislav N. Gorb and Thies H. Büscher, the team selected eggs from seven phasmid species chosen specifically to represent the extraordinary morphological diversity of the order. Among them were the small capitulate eggs of Carausius morosus, the large capitulate eggs of Tirachoidea jianfenglingensis, lentil-shaped eggs of Dajaca napolovi, pinnate eggs of Phyllium mabantai, hairy eggs of Orestes draegeri, rough-surfaced eggs of Nuichua rabaeyae, and the eggs of Sungaya aeta, which females bury using a secondary ovipositor. By spanning this range of shapes, sizes and surface structures, the experimenters aimed to determine whether any egg morphology confers a survival advantage during a trip through a bird’s digestive tract.

The feeding experiments used domestic pigeons, Columba livia f. domestica, as the granivorous test subjects. For each trial, batches of 16 to 25 eggs from a single species were packed into a one-milliliter gelatin capsule that was placed deep into the bird’s throat to guarantee swallowing, sidestepping the possibility that pigeons might simply crush the eggs with their beaks. Each pigeon was then housed individually for 24 hours in a nest box fitted with a wire mesh grid above a paper sheet, allowing droppings to be collected and sieved for eggs and egg fragments. Every recovered intact egg was incubated on damp paper towels at room temperature and monitored daily for hatching. The stakes of this design were clear: any egg that survived the full digestive journey and later produced a nymph would constitute direct evidence of ornithochory, the bird-mediated dispersal conventionally associated with plants.

The results were unambiguous. Across all seven species, most eggs emerged from the pigeons ground into tiny fragments, and not a single egg that passed through the digestive system hatched afterward. The lone partial exception was Dajaca napolovi, the species with disc-shaped eggs: eight of the fifty eggs fed to pigeons were recovered structurally intact from the droppings, along with assorted eggshell pieces from other species. Interestingly, the fatty capitula of several species frequently emerged fully undamaged, a testament to the resilience of that lipid-rich structure, but capitula alone cannot hatch. The mechanical gizzard, with its grinding stones, had effectively destroyed the embryos of every species regardless of how convincingly their eggs resembled seeds. The finding echoes earlier work by Matan Shelomi, who in 2011 fed more than 900 phasmid eggs to quails and chickens and recovered only one unbroken egg.

Yet intactness alone does not guarantee viability, and this is where the study’s laboratory simulations proved decisive. The researchers dissected the digestive gauntlet into its three principal stressors: acidity, heat and mechanical abrasion. They subjected batches of 50 eggs each of Carausius morosus and Dajaca napolovi to distilled water at 38 to 42 degrees Celsius to mimic avian body temperature, to hydrochloric acid diluted to a pH of 1.9 to 2.2 matching the avian proventriculus, and to vigorous stirring with two-to-three-millimeter stones replicating gizzard action. A fourth treatment combined all three stressors, and untreated control groups allowed baseline hatching rates to be established. Eggs were then incubated for months, because phasmid embryos are famously patient, sometimes taking more than half a year to emerge.

Acidity emerged as the silent killer. In the control groups, 70 percent of Carausius morosus eggs and 72 percent of Dajaca napolovi eggs hatched, but after acid exposure the hatching rate for both species was zero. Scanning electron microscopy revealed why: the acid attacked the chorion, the outer eggshell, dissolving its mineralized layers and leaving holes, structural damage and crystalline precipitates that likely represent calcium salts leached from the shell. Phasmid eggshells are known to incorporate biomineralized material, including calcium oxalate, which lends rigidity against physical threats but turns out to be chemically vulnerable in strong acid. The findings align with prior research showing that acid exposure dissolves the calcium oxalate-rich middle layer of the chorion and degrades its mechanical properties, and with studies on mayflies and mosquitoes demonstrating that low pH disrupts embryonic development in other insects as well.

Heat and mechanical stress produced species-specific effects. For Carausius morosus, a species native to India where pre-monsoon temperatures routinely climb above 35 degrees Celsius, the heat treatment was surprisingly benign: 60 percent of heated eggs still hatched, albeit after a longer incubation of about 112 days compared to roughly 80 days in controls. Dajaca napolovi, which inhabits cooler mountainous regions of northern Vietnam, fared poorly under the same thermal challenge, with only two of 50 eggs hatching after incubation periods exceeding 200 days. Mechanical stirring with stones crushed most Carausius eggs, but a larger share of the slippery, disc-shaped Dajaca eggs survived, and ten of those hatched. Friction experiments on a motorized tilting stage explained the disparity: Dajaca napolovi eggs slid at angles as low as roughly 5 degrees on smooth substrates, compared with more than 22 degrees for Carausius morosus, meaning the Vietnamese species’ low-friction eggs may simply slip between gizzard stones rather than being crushed between them.

Synthesizing the feeding trials and the simulations, the authors conclude that successful bird-mediated dispersal of a single phasmid egg through a granivorous bird would require a trifecta of preadaptations: mechanical toughness or slipperiness to survive the gizzard, chemical resistance to withstand gastric acid, and thermal tolerance to endure body temperatures around 40 degrees Celsius. No species tested possessed all three. Even the eight structurally intact Dajaca eggs recovered from pigeon droppings failed to hatch, most likely because the acidic phase of digestion, not the mechanical phase, had already doomed their embryos. For the investigated phasmatodean species, long-distance dispersal via granivorous birds therefore appears highly unlikely, and the visual mimicry of seeds seems to serve other purposes, such as defense against egg parasites, rather than a ticket through a pigeon’s gut.

The story may not be over, however, because not all birds digest seeds the same way. Previous work by Kenji Suetsugu and colleagues showed that when eggs excised from gravid females of three phasmid species were fed to insectivorous brown-eared bulbuls, five to twenty percent remained intact depending on species, and two eggs of the flightless Japanese stick insect Ramulus mikado actually hatched. Phylogeographic analysis of Ramulus mikado has since provided evidence consistent with historical long-distance dispersal, and the facultative parthenogenesis of many phasmids means that viable eggs inside a gravid female could potentially survive her predation and be dispersed when the female herself is eaten. Because insectivorous birds lack the stone-filled gizzards of seed-eaters and process prey differently, the digestive conditions their eggs encounter may be far gentler. The Kiel team suggests that future research should examine the digestive physiology of frugivorous and insectivorous birds and the protective role of the maternal body, to determine whether rare dispersal events through predators, rather than through seed-mimicry, could explain how flightless stick insects colonize distant habitats. For now, the seed disguise remains a marvel of convergent evolution, but as a dispersal strategy aimed at granivorous birds, it appears to be a costume without a function.

Beyond the immediate question of bird digestion, the findings carry weight for a broader puzzle in phasmid biology: how flightless, slow-moving insects achieve the geographic isolation that drives speciation. With wings reduced or absent in many species and even functional wings rarely used, adult stick and leaf insects have few options for crossing inhospitable terrain. Passive transport of the egg stage has therefore long been considered the most plausible route to new habitats, making the fate of eggs inside potential animal vectors a matter of evolutionary consequence rather than mere curiosity.

The study also highlights how little is known about the chemical ecology of phasmid eggshells. The biomineralized layers that give the eggs their rigidity appear to be a double-edged adaptation, hardening the shell against physical hazards while creating a chemical vulnerability to the low pH of a bird’s proventriculus. Understanding how different species vary the composition and thickness of these layers could reveal whether any lineage has evolved genuine resistance to gastric conditions.

There is an ecological irony in the results as well. The capitulum, the lipid-rich appendage atop many phasmid eggs, chemically and visually mirrors the elaiosome of myrmecochorous seeds, and ants respond to it similarly, carrying eggs into their nests and gnawing off the capitulum without harming the embryo. Ant-mediated dispersal, unlike bird-mediated dispersal, involves no grinding gizzard and no strong acid, suggesting that the seed-mimicry of phasmid eggs may be aimed at a much smaller and far more forgiving partner than the birds the resemblance superficially invokes.

Subject of Research: Experimental testing of whether stick and leaf insect (Phasmatodea) eggs can survive digestion and dispersal by granivorous birds.

Article Title: Can granivorous birds disperse stick and leaf insect eggs? Integrating in vivo digestion trials and in vitro functional experiments

Article References: Burack, J., Haase, E., Gorb, S. N., & Büscher, T. H. (2026). Can granivorous birds disperse stick and leaf insect eggs? Integrating in vivo digestion trials and in vitro functional experiments. The Science of Nature, 113(5), Article 106. https://doi.org/10.1007/s00114-026-02157-5

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02157-5

Keywords: Phasmatodea, stick insects, egg dispersal, ornithochory, granivorous birds, pigeons, seed mimicry, gizzard, gastric acid, eggshell biomineralization, friction, zoology