It’s something out of an arachnophobe’s worst nightmares. Earlier this month, residents from the Southern Tablelands region in southeast Australia reported seeing millions of spiders falling from the sky and blanketing the area in webs.
“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,”
local resident Ian Watson said, describing the scene to the Sydney Morning Herald.
Martyn Robinson is a naturalist at the Australian Museum in Sydney. He explains that the phenomenon is likely a result of two unique spider adaptations.
The first is a migration technique known as “ballooning”: spiders (usually babies but sometimes adults as well) will climb to the top of a tree and release strands of silk that catch in the wind, lifting them aloft. The spiders can reach altitudes of nearly 2 miles using this technique.
“They can literally travel for kilometres … which is why every continent has spiders. Even in Antarctica they regularly turn up but just die,” Robinson said, adding, “That’s also why the first land animals to arrive on new islands formed by volcanic activity are usually spiders.”
The other adaptation is a survival technique in which spiders will use vegetation to find higher ground during floods. It often occurs at the same time as ballooning, according to Robinson.
“When the ground gets waterlogged, the spiders that live either on the surface of the ground or in burrows in the ground, come up into the foliage to avoid drowning,” Robinson explains.
To get to the top of the vegetation, ground spiders throw up silk “snag lines” (not unlike the lines used in ballooning), and then haul themselves to safety once the lines catch on something. During severe floods, the effect of all this web-throwing is particularly pronounced:
“Everywhere a spider goes it leaves a trail of silk … so if they use somebody else’s silk line, they put their silk line over that. You end up with thick silk roads … criss-crossing finer silk lines to produce this interwoven shroud,”
According to The Daily Mail, the spiders’ webs covered entire houses and fields in the Southern Tablelands, but disappeared overnight amid cold temperatures.