IN FOCUS: THE AUSTRALIAN BOTANIC GARDEN
A BEAUTIFUL
NOISE
DON’T KNOW YOUR RAZOR GRINDER FROM YOUR FENCE BUZZER? THE GARDENS’ CELEBRATED
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reek poets have written odes to them. French sculptors have crafted them. And Chinese artists have embraced them as motifs since the Shang Dynasty. So why does the cicada seem so quintessentially Australian? The answer is that while plenty of cultures might worship these boisterous bugs, Australia is the undisputed cicada capital of the world. Of the 3,000 or so cicada species spread across every continent other than Antarctica, more than 800 of them are found only in Australia. And among our endemic collection are the two intriguing specimens that entirely make up one of the two cicada families – the Tettigarctidae, also known as the hairy cicadas. Botanic gardens are often great places to encounter cicadas and at the Australian Botanic Garden Mount Annan visitors might also, if they’re lucky, spot one of the country’s leading experts on the creatures, Restoration Biology Officer Dr Nathan Emery. Nathan became an aficionado as a child, when his father took him and his siblings on cicada-spotting field trips around Sydney’s national parks. It’s a passion that father and son still share today. In fact, over the past eight years, the pair have identified around a dozen new species in New South Wales and Western Australia, the most recent being the Dharug Squeaker (Haemopsalta eximia), which they discovered in northwest Sydney.
24 THE GARDENS SUMMER 2021–2022
Given cicadas are the loudest insects in the world, they are of course virtually impossible to ignore during an Australian summer. But what might surprise people, says Nathan, is just how little we know about them. “We have more cicadas than any other country, yet around half of them have yet to be scientifically described,” he says. “Australia has such diverse species due to our distinct vegetation communities and our long isolation. Our cicadas are also more unpredictable than those in other parts of the world – we don’t know what triggers their emergence, whereas in America, for instance, they can pinpoint down to the
Dr Nathan Emery with a Dharug Squeaker
week when some species will emerge.” What we do know about the cicada lifecycle is that after mating, adult females lay their eggs in plant stems. The eggs hatch and small wingless nymphs fall to the ground and burrow below the surface where they live – sometimes for many years – and feed on the sap from plant roots. When a nymph reaches full size, it digs its way to the surface (usually emerging at night in late spring or early summer) and climbs on to a tree trunk or other object to moult (shed its skin). One of the things we are unclear about, says Nathan, is whether different cicada species prefer specific trees. “We know there are plants some cicada species favour. For instance, the Green Grocer prefers leafy trees that offer good canopy cover for protection from predators. Another green coloured species, the Bladder Cicada, prefers plants that have dense green leaves or thick shrubs and hedges, which offer camouflage. “What we are also starting to see through my citizen science project, the Great Cicada Blitz, is a greater preference for native species, such as eucalypts, callistemons and melaleuca. Because nymphs live so many years underground, it could be they want to ensure their brood is associated with plants that are more likely to survive for that time. But it could also be about the nutrient levels in the tree sap or camouflage. The fact is we still have a
Photos: Dr Nathan Emery
CICADA EXPERT DR NATHAN EMERY IS HERE TO HELP. DAVID CARROLL REPORTS.
