A region in Australia’s southeast has been cloaked in sheets of web after floodwaters forced thousands of spiders to find higher ground.

Residents in Victoria’s Gippsland region witnessed the spectacle after intense rain and heavy flooding rocked the area last week, damaging dozens of homes and leaving two people dead.

The waterlogged soil sent thousands, possibly millions of spiders scrambling for refuge on plants, signs and anything else above ground.

“We are constantly surrounded by spiders, but we don’t usually see them. They are hiding in the leaf litter and in the soil,” Lizzy Lowe, a postdoctoral researcher at Macquarie University, wrote in an explainer about the phenomenon for The Conversation.

“When these flood events happen, they need evacuate quickly up out of holes they live in underground. They come out en masse and use their silk to help them do that.”

Baby spiders use the same technique of letting out strands of their silk, known as ballooning, to catch the wind and disperse after emerging from egg sacs. 

Simultaneous ballooning by thousands of spiders results in the blanket silk effect, called gossamer.

The mass evacuation in Gippsland is likely to be a combination of many different adult spiders, Lowe wrote. This effect can be seen in other parts of Australia and the world after flood events.

Ken Walker, a senior curator of entomology at the Melbourne Museum, told The Guardian that the gossamer effect occurs semi-regularly in Victoria during the wet season in the winter.

“What’s happened is there’s been a massive flooding event pretty quickly … so they’re using the ballooning not to escape for hundreds of kilometres but to almost throw up a lasso on top of the vegetation. It hooks on to the tops of the vegetation because it’s lighter than air, and then they quickly climb up.”

Local council member Carolyn Crossley shared a video of the effect and asked for support for the Gippsland Emergency Relief Fund, which is providing assistance to areas hit hard by the floods.

Locals were advised to leave the spiders alone. The webbing will break up on its own, and the arachnids will likely soon disperse and head back to their underground homes, Walker said.