'Ballooning' spiders leave behind sea of silk after flood in Australia

Many residents of Victoria, Australia, evacuated their homes to avoid disastrous floods last week — and upon their return, they found the land, trees and road signs coated in thick veils of shimmering spider silk, according to news reports.

Heavy rains and strong winds triggered flash floods in the Australian state last week, leaving tens of thousands of residents without power, The Guardian reported; two people died when their vehicles became inundated by the floodwaters. The Victoria State Emergency Service had issued flood warnings beforehand, specifically urging residents to evacuate from the Traralgon Creek area, located in the rural Gippsland region of Victoria, according to tweets from Darren Chester, the member of Parliament representing Gippsland.

As the residents of Gippsland evacuated their homes, local arachnids also fled for higher ground. Using a behavior called "ballooning," spiders clambered atop vegetation and flung fine silk threads into the wind; as the threads caught air, the spiders got plucked from their perches and lifted to safety, CNN reported.   

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"When we get these types of very heavy rains and flooding, these animals who spend their lives cryptically on the ground can't live there anymore, and do exactly what we try to do — they move to the higher ground," Dieter Hochuli, an ecologist at the University of Sydney, told CNN affiliate 7News. "This is a surprisingly common phenomenon after floods," he said, adding that sheetweb spiders — a family of arachnids in the genus Stiphidiidae — likely spun the abundance of silk.

When thousands of spiders balloon at the same time, their many silk threads can merge to form a "remarkable carpet of silk, called gossamer, covering shrubs or fields," according to the Australian Museum. Given how much gossamer accumulated in Gippsland, it's possible that millions of spiders took to the air to escape the floods, Ken Walker, a senior insects curator at Museums Victoria, told The Age, a Victoria-based newspaper.  

"To me, it's absolutely beautiful. A silken blanket that undulates throughout vegetation," Walker said. "It also shows the literally tens of thousands, if not millions, of spiders at ground level. Without spiders, we'd have plagues of insects," he added.

Local councillor Carolyn Crossley told BBC News that she noticed the "beautiful" sheets of spider silk while assessing flood damage in the area on Monday night (June 14). "The fact that it didn't separate — it was like these spiders had coordinated to make this incredible landscape art installation or something," she said. Crossley had witnessed this ballooning phenomenon before but never to such a dramatic extent, she said.

The billowing mats of spider silk should disintegrate sometime this week, BBC News reported. Meanwhile, Gippsland continues to recover from the severe flash floods.

Originally published on Live Science.

Nicoletta Lanese
Channel Editor, Health

Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.