Tag Archives: the biggest spider in Britain

Fen Raft Spider breeding project

Spider expert Helen Smith has been raising thousands of Fen Raft Spiders in her kitchen, feeding them flies in their test tube nurseries.  But now the surrogate mother has broken the bond and the spiderlings have to go it alone, after being set free in a Suffolk nature reserve.  The Fen Raft spider is a seriously endangered species, one of only two protected spiders in Britain, living in isolated enclaves.  The parents of this new generation of spiderlings were picked from separate populations to enhance their genetic diversity.

The Raft Spider – Britain’s largest spider

In fact two spiders qualify for this title, but they are so similar that only experts can tell them apart: Dolomedes plantarius and Dolomedes frimbiatus – the Raft Spiders. The females can span an impressive 7 cm, from leg-tip to leg-tip, with a body of up to 22mm. The males, as usual in spiders, are notably smaller, with a body of 10 -13mm.

Chocolate brown, with creamy white stripes, Raft Spiders live in watery habitats, typically fens and marshes.  They are found at the water’s edge, resting their legs on the surface. Vibrations in surface tension inform them about what’s happening in their vicinity. Continue reading The Raft Spider – Britain’s largest spider