Scientists in Australia have found two new species of giant stick insects, including one whose lidlike eggs have never been documented in the group before. The discovery also showed that a well-known stick insect had been incorrectly identified for decades, highlighting how much biodiversity may remain hidden in plain sight.
The University of Sydney’s research group went back to Australian members of the stick insect genus Anchiale and found two new species. One of those has eggs that carry an unusual lidlike structure. The team also brought back into recognition a third species that had slipped unnoticed for decades.
The researchers found that insects previously grouped as two species are actually five distinct species. They range from northern New South Wales up along the coast of Queensland and into tropical northern Australia.
Hidden Diversity Among Familiar Insects
The scientists arrived at their conclusions even though there is already a great deal of knowledge about Australian stick insects. The insects have been studied scientifically for decades, and more than 1000 citizen science observations have been submitted through iNaturalist and the Atlas of Living Australia.
The researchers still maintain that a great deal of Australia’s insect variety has yet to be recorded.
Dr. Braxton Jones, lead author from the Aola Richards Sydney Insect Hub at the University of Sydney, said the findings show just how much there is left to discover about insect life on Earth.
Fun Facts About Stick Insects
Some species of stick insect reproduce without the need for a male partner at all. In these cases, a female creates eggs through a method called parthenogenesis, wherein those eggs grow into female-only young that are exact copies of their mother.
Predators who try to eat certain stick insects may find themselves sprayed with chemicals. Those chemicals can irritate the eyes and mouth of the creature doing the attacking.
The longest stick insect ever recorded in Australia measures around 62cm, with the world record standing at 64cm. The country is home to roughly 130 known species, which makes up a significant portion of the roughly 3609 species that exist across the globe.
These insects come from a group known as Phasmatodea, whose name is drawn from an ancient Greek term meaning “phantom” or “ghost.” Their camouflage is so effective that they can disappear entirely among leaves and branches.
A few kinds of creatures can gradually shift their hue to suit their setting. Their look can move from green to brown, and certain ones can come to resemble lichen as they settle into leaves, bark, and branches.
The young of the stick insect Extatosoma tiaratum employ a most singular method of preservation. Upon leaving the egg, the small nymphs have been seen departing from ant nests while appearing and acting much like ants themselves. The eggs may be conveyed into ant nests, where they lie dormant for months, gaining shelter from wasps. Once hatched, these young insects rely on their ant-like hue, form, and manner to pass without notice up the trunk of a eucalyptus tree.
When threatened, some stick insects reveal brightly colored wings, startling predators through sudden display. Some species go further, producing a rustling noise with their wings, thus incorporating sound into their defensive wing design.
When a predator grabs a stick insect by its leg, certain species can break off the limb on purpose to get away. The act of cutting it off is called autotomy. Juvenile stick insects can grow back the missing leg through later shedding of their skin, slowly replacing what was lost.
A Stick Insect Misidentified for Decades
Among the study’s most unexpected findings was a large stick insect that has long been known to both scientists and insect enthusiasts.
Museum specimens, field surveys, citizen science observations, and studies of insects raised in captivity all fed into a research effort that also drew on DNA analysis. That combined body of evidence revealed that the insect had been misidentified for decades.
It is now recognized as a separate species called Anchiale robusta.
The findings are published in Austral Entomology.
A New Species From the Mabi Rainforest
A new species was formally described by the researchers, and it comes from the critically endangered Mabi rainforest of Queensland’s Atherton Tablelands. The species is named Anchiale mabiensis.
The eggs of this species carry a distinctive lid-like structure that has never before been recorded in stick insects or their nearest kin.
Discovery Could Help Forestry and Agriculture
The revised classification may also have practical value.
A stick insect that is sometimes seen in numbers so large it strips trees bare has now been discovered to include more than one distinct species. Sorting these species apart may give researchers and land managers a clearer picture of how they will affect forestry and farming down the line.
Researchers are pointing toward a possible new species from Cape York, one they think has not yet been described. Before they can confirm its identity, however, they say they need more specimens.
Jones made the statement “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.”, according to Dr. Jones.
The Commonwealth Department of Climate’s National Taxonomy Research Grant provided the money behind the project, with support coming through the Australian Biological Resources Study.
What We Know So Far
| Species | Location | Key Feature |
|---|---|---|
| Anchiale robusta | Northern NSW, coastal Queensland, tropical northern Australia | Misidentified for decades |
| Anchiale mabiensis | Mabi rainforest, Atherton Tablelands | Lidlike egg structure |
| New Cape York species | Possible | Undescribed |
New species continue to turn up even in places that researchers have examined closely for years, and a single discovery can make all the effort worthwhile. That stick insect with lidlike eggs provides a perfect example.
For years, researchers were tricked by a large stick insect, and there is little reason to believe that it will remain the sole instance of its kind deceiving science.
Source material: “This giant stick insect fooled scientists for decades,” ScienceDaily.
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