Fen raft spider

Big and beautiful! The Fen raft spider is a large and beautiful spider. Females can reach up to 7cm across (including legs!), the body is a rich brown or black colour with white or cream stripes along the sides of the cephalothorax and abdomen.

Fast Facts

Latin name: Dolomedes plantarius

Notable feature: The body is a rich brown or black colour with white or cream stripes along the sides of the cephalothorax and abdomen

Hairy Legs

Fen raft spiders live in fens and other wetlands in southern England and Wales. They are able to sit on the surface of the water and move across it thanks to their hairy legs. These hairs are also very sensitive and are used to detect the movement of their prey. Fen raft spider diet is mostly made up of other invertebrates such as small spiders, dragonfly larvae and pond skaters, however the spiders have been known to catch small vertebrates such as fish and tadpoles!

Caring Parents

Female Fen raft spiders are very caring mothers. After mating the females build an eggs sac which they carry for approximately three weeks, dipping the egg sac in the water every few hours to keep the eggs moist. When it is time for the eggs to hatch the female builds a nursery web – a silken tent of up to 25cm across which is suspended above the water attached to plants. The mother spider will guard her nursery for the first week of the young spiders lives after which they will disperse into the surrounding vegetation.

Conserving the Fen raft spider

Only three populations of the Fen raft spider are known in the UK: Redgrave and Lopham Fen in Suffolk, the Pevensey levels in East Sussex, and Pant-y-Sais Fen and Crymlyn Bog near Swansea.

Due to its rarity, the risk of extinction of this spider is high, it is therefore a protected species under the Wildlife and Countryside Act, and is a priority species for conservation action under the UK Biodiversity Action Plan.

Fen raft spider art project!

Buglife are partners on an exciting project to bring together spiders and art – an art exhibition will open at Redgrave and Lopham Fen in late October. Please click here for more details.