Fen Raft Spider Dolomedes plantarius

The Fen Raft Spider (Dolomedes plantarius) is one of Britain’s largest and rarest spiders, and Suffolk’s Waveney Valley is one of only three sites in the UK where it is known to breed – making the county central to its national survival. A semi-aquatic predator, it hunts across the water surface of base-rich, unpolluted ditches and grazing marsh in open fen, detecting vibrations to locate invertebrate prey and occasionally small fish or tadpoles. Females construct a distinctive nursery web in emergent vegetation to protect their egg sac and young. An intensive conservation programme – involving habitat management, captive breeding, and reintroduction – has helped to stabilise and expand the Waveney Valley population, and the species has become a symbol of fen conservation in Suffolk. Image: © Neil Rolph, Flickr.

Find out more: iNaturalist, British Arachnological Society, Suffolk Wildlife Trust, Suffolk LNRS information page