Fen raft spider Dolomedes plantarius

The fen raft spider is a large, dark brown spider that lives around the edge of ponds and ditches. Adults sit at the edge of the water, or on floating vegetation, with their front legs resting on the water's surface in order to feel for the vibrations of potential prey. Using the surface tension of the water, they chase out on to the water to catch their prey, which are mainly invertebrates, but will also include vertebrates, such as tadpoles or small fish. Fen raft spiders will also go underwater, either to hunt or when threatened.

Conservation status

Very rare. UK Biodiversity Action Plan priority species. Protected under Schedule 5 of the Wildlife and Countryside Act 1981. Classed as ‘vulnerable’ on IUCN’s species Red List.

Details

Did you know? Juvenile fen raft spiders are able to regenerate lost limbs, which are often shed when individuals are grabbed by a predator. This ability disappears once they become adults, though this does not prevent their ability to function – remarkably, adult females with only 3 legs have been seen effectively guarding their nursery webs.

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