Why It's Not Actually Raining Spiders in Australia

Web Masters: Silk covering paddocks outside of Goulburn, Australia. Keith Basterfield

The town of Goulburn, in southeast Australia, got a charming little surprise this month when millions of spiders decided to blanket the countryside in their webs and float about in the air, buoyed by little parachute-like extensions of silk.

Breathless reports from around the interwebs took this information and spun a good yarn about how, horrifyingly, it has been "raining spiders."

But this actually goes on all the time in nature. Thousands of species of spiders regularly spin a little bit of silk when they are young and release it into the air to try and get a lift from the breeze, a process called ballooning. They do this to disperse, to find new territory and to distance themselves from their often cannibalistic kin. Usually, however, there aren't enough spiders for it to be noticeable.

Web Cast: Spider silk surrounding the landscape in Wagga Wagga, Australia. Daniel Munoz / Reuters

In this case, however, the exact right atmospheric conditions came together to induce million of spiders to balloon all at once. Specifically, there was rain followed by warmer weather. "It has been raining a lot down here, but not spiders," says Lizzy Lowe, an arachnology doctoral student at the University of Sydney. Lowe explains that the water-logged land led to spiders producing strands of silk to try and hitch a ride in the wind. "All of the tiny little spiders that we don't normally notice are just trying to get away from the flooded areas," she says. The warm weather produces updrafts that spiders can catch and float away.

Although this tactic usually only transports them a small distance, it can sometimes take them quite far. Scientists have found spiders as high as 15,000 feet up in the air and as far as 200 miles off the coast, says Rick Vetter, a retired arachnologist at the University of California at Riverside.

Web Sight: A dog walking through spider silk in Wagga Wagga in 2012. Daniel Munoz / Reuters