To become Australians, these spiders crossed an ocean


It’s easy to think that the globe’s vast oceans would be effective barriers to the movement of land animals. An elephant can’t swim across the Pacific, after all. But it turns out that plenty of plants and animals — and even people — have unintentionally floated across oceans from one continent to another. Now comes evidence that tiny, sedentary trapdoor spiders made such a journey millions of years ago. That voyage took them from Africa all the way across the Indian Ocean to Australia.

Moggridgea rainbowi spiders can be found on Kangaroo Island. It sits off the south coast of Australia. These trapdoor spiders build a silk-lined burrow in the ground with a secure-fitting lid, notes Sophie Harrison. She is a biologist in Australia at the University of Adelaide. The burrow and trapdoor provide these spiders with shelter and protection. It also offers them an out-of-sight spot from which to await approaching prey. And it means that the spiders don’t really need to travel more than a few meters (yards) over the course of a lifetime.

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