Ask A Biologist: Why Are There No Big Spiders In Iceland?

Spiders in Iceland seem, anecdotally, few and small. We asked Dr. Gísli Már Gíslason, Professor of Biology at the University Of Iceland, why there are no large arachnids around.

This question is a bit misleading. All really big spiders (and many other terrestrial arthropods) are found in the tropics and warmer regions of the world, like Australia. Iceland, however, is an island in the lower Arctic or higher Boreal region, where very big spiders are not found naturally.

There are 91 species of spider in Iceland—none of which are poisonous to humans— plus the occasional visitor or migrant. This is a small number, compared with 44,000 species known worldwide. Iceland is an isolated island in the mid-North Atlantic, which has only been colonized by terrestrial invertebrates from the last Ice Age (11,000 years ago).

Occasional visitors like Tarantula spiders (among the biggest in the world) with a body size up to 20 cm have been found in Iceland. However, these big spiders are imported by goods or by humans as pets from warmer countries.

The biggest native spider species in Iceland is the Common Garden Spider (“Krosskönguló” in Icelandic, Araneus diadematus). The female body length can reach 20mm (males are smaller, up to 13mm). It is found on house walls and cliffs facing the sun in all of Iceland’s lowlands, with distribution around the North Pole and south to the Mediterranean and Mexico. This species is among the largest native species in Northern Europe.

It is therefore a wrong assumption that big spiders are not found in Iceland, if one keeps in mind its position and latitude.

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