Spider Swarm.

In an arachnophobe's worst nightmare, swarms of spiders spin webs in a bush in flood-ravaged Wagga Wagga (map), Australia, Tuesday.

After a week of record rain, floodwaters across eastern Australia have forced the ground-dwelling spiders—and at least 13,000 people—to flee their homes, according to Reuters.

The rampant webs blanketing vast stretches of Wagga Wagga are likely "a dispersal mechanism that allows [spiders] to move out of places where they'd surely be drowned," said Robert Matthews, a professor emeritus of entomology at the University of Georgia.

Producing large quantities of silk creates a sort of "vast trampoline" that supports the spiders as they're fleeing the water, he noted.

Matthews added he he has never seen such a "striking phenomenon."

Spiders spin thick webs as floods force them to move to higher ground in Wagga Wagga, Australia, on Tuesday.

The wet year may have has led to a boom in insects in this region of Australia—an abundant food source that's also likely inflated spider numbers, Matthews said.

River-Spanning Spider Web

A river-spanning spider web dwarfs a park ranger in Madagascar in 2008. Made of the world's strongest known biological material, the web is the product of a new species, the Darwin's bark spider, which makes the world's largest webs of any single spider, new studies say.

Zoologist Ingi Agnarsson and colleagues have found Darwin's bark spider webs as wide as 82 feet (25 meters)—about as long as two city buses.

In Andasibe-Mantadia National Park (pictured), "the park rangers knew about them, and I think they've shown them to tourists for a while," said Agnarsson, of the University of Puerto Rico.

But the Darwin's bark spider and its record-breaking webs were unknown to science until they were documented by the team, whose findings appear this week..............