Raft Spiders

Raft Spider (Dolomedes Fimbriatus)

One of the UK’s largest Spider is the semi-aquatic, Raft Spider (Dolomedes Fimbriatus), also known as the Fishing Spider.  With a leg span of 7cm, Raft Spiders spend their lives in surrounding pond vegetation that’s close to the water’s edge.  They spend much of their time resting their front legs on the water surface. This is because their legs have sensory hairs that can detect vibrations in the water from visiting wildlife such as small Fish, Dragonfly and Damselfly larvae, Pond Skaters, and Tadpoles. These are are all on the menu for a Raft Spider, along with any unfortunate winged insect that happens to fall into the water.  

Raft Spiders are quite rare so you are unlikely to find them in your back garden pond.  Due to the loss of wetlands and pollution, they are now only found in scattered locations throughout the UK.  Raft Spiders favour acidic water and fresh water habitats such as natural ponds, fens and marshlands.

Life Cycle

Like many land Spiders, Raft Spiders live 2-3 years.  The females lay up to 100-200 eggs which she will carry around under her abdomen in a attached silk egg sack.  She  will regularly dip this sack into the water to prevent the sack from drying out and just before the eggs hatch out, she creates a webbed tent above the water margin in the surrounding pond vegetation to protect her young and to create a safe haven for them once they have hatched.  Like many other Spiders, she is fiercely protective of her young and will be on constant guard until the Spiderlings become independent.

The Fen Raft Spider (Dolomedes Plantarius)

Also known as the Great Raft Spider, this species is extremely rare and therefore, is highly protected.  This Spider is only found in three small locations in the UK and in 2010, over 1500 Spiderlings were re-introduced to the Suffolk Wildlife Trust Nature Reserve..

Please visit my website www.lilieswatergardens.co.uk to read over 120 informative articles on aspects of water gardening and the numerous wildlife that fresh water attracts.