When spiders fall from the sky

In southern Australia, it’s raining spiders. Spiders can ride the wind using an ingenious migration technique known as ballooning. Residents of Goulburn, Australia, received a startling demonstration of the phenomenon last week, when hundreds of thousands of tiny spiders descended from the sky on gossamer parachutes. “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,” says Goulburn resident Ian Watson.

In order to balloon, spiders find an elevated launching point on a plant or a fence, stick their spinnerets into the air, and release a fine silk line called gossamer, forming a triangular balloon or parachute. Once the balloon is picked up by the wind, the spiders are lifted up and dispersed to new locations across many miles. This impressive technique explains why spiders are scattered all over the world, including Antarctica. What triggers spiders to go aloft, however, remains unclear, and it’s unusual for millions of spiders to land in the same place. Scientists say changes in weather or wind patterns may have resulted in Goulburn’s spider downpour.