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Why spooky spiders rained from the sky in Australia

A house is surrounded by spiderwebs next to flood waters in Wagga Wagga on March 6, 2012. Residents of nearby Goulburn saw a similar phenomenon this month, after millions of spiders reportedly descended on the Australian town. (Daniel Munoz/Reuters)

Residents of Goulburn, Australia, awoke this month to find their town shrouded in eerie, silken webs, while millions of tiny spiders rained down from above, local news reported.

“The whole place was covered in these little black spiderlings and when I looked up at the sun it was like this tunnel of webs going up for a couple of hundred meters into the sky,” resident Ian Watson told the Sydney Morning Herald. His house looked like it had been “abandoned and taken over by spiders,” he added.

Mystified by the phenomenon — and frustrated by the tiny arachnids getting caught in his beard — Watson did what anyone in his situation would do: He turned to the Internet.

“Anyone else experiencing … millions of spiders falling from the sky right now?” he wrote on Goulburn’s community Facebook page, according to the Morning Herald. “I’m 10 minutes out of town and you can clearly see hundreds of little spiders floating along with their webs and my home is covered in them. Someone call a scientist!”

It’s not clear if anyone did pick up their phone, but if they had, scientists could have assured the people of Goulburn that their predicament is not without precedent. Similar incidents have been documented recently in Texas and Brazil and nearby Wagga Wagga, another Australian town.

“Spider rain” happens when large groups of arachnids migrate all at once, using a technique called “ballooning.” According to a 2001 study in the Journal of Arachnology, the spiders will spin out dozens of silk strands at once so that they fan out and form a triangular parachute, allowing the clever critters to catch a breeze toward new ground.

Rick Vetter, an entomologist at the University of California at Riverside, told Live Science that many spiders use ballooning — usually just not all at once.

“This is going on all around us all the time. We just don’t notice it,” he said.

It’s a useful skill to have if you’re a tiny arachnid — far faster than walking on your own eight legs. According to Martyn Robinson, a naturalist at the Australian Museum, spiders can travel for miles this way.

“[Ballooning] is why every continent has spiders. Even in Antarctica they regularly turn up but just die,” he told the Sydney Morning Herald. “That’s also why the first land animals to arrive on new islands formed by volcanic activity are usually spiders.”

When the aerial arachnids land, their silk balloons wind up draped over the landscape. This effect, sometimes called “angel hair,” also happens after heavy rains or floods, Robinson said. Spiders that live in the ground will throw silk “snag lines” into the air and use them to haul themselves up out of the waterlogged earth. When huge numbers of spiders escape drowning this way, their criss-crossing “silk roads” weave a shroud over trees, grass and sometimes buildings.

The effect rarely lasts long, but it gives ordinary buildings and fields a distinctly haunted look. Which means that lots of people are ready to forgo the scientific explanation for an otherworldly one. People who believe in UFOs often cite “angel hair” incidents as evidence.

Last fall, Roberto Pinotti, the president of Italy’s National UFO Center, spoke to the BBC about his own angel hair sighting, a 1954 incident in Florence.

“I remember, in broad daylight, seeing the roofs of the houses in Florence covered in this white substance for one hour and, like snow, it just evaporated,” he said. The substance appeared at the same time that spectators at a local soccer game spotted several strange objects in the sky above the stadium, and Pinotti is not convinced that spiders were to blame.

“Of course I know about the migrating spiders hypothesis — it’s pure nonsense. It’s an old story and also a stupid story,” Pinotti told the BBC.

But astronomer James McGaha, who works at the Center for Inquiry’s Grassland Observatory and works to debunk paranormal theories, said much the same thing about Pinotti’s beliefs.

“It’s an absolutely silly idea. Science totally rejects this idea,” he said of the UFO explanation.

“This was actually caused by young spiders spinning webs, very, very thin webs,” he told the BBC. “As some of this stuff breaks off and falls to the ground, this all seems magical of course. … But I’m fairly confident that’s what happened that day.”