Raft spider
Dolomedes fimbriatus
The raft spider (Dolomedes fimbriatus) lives along the banks of standing or slowly flowing waters. It is perfectly adapted to life in the peatland. It can run across the water surface and also dive. Raft spiders do not build webs. Instead, they lie in wait for prey on the water surface. Sheltered by plants, they hunt insects, tadpoles and even small fish and frogs.
1 – Body Length
With a body length of 1 to 2.2 cm, the raft spider is one of the largest spiders in Central Europe.
2 – On the Water, In the Water
Despite its relatively heavy body, the raft spider can run on water. Its dense hairs help it do so. When threatened or hunting, it dives below the surface. Underwater, it rows with two pairs of legs.
3 – Distinctive Markings
The raft spider takes its name from the white to yellowish longitudinal stripes along its body.
4 – 1,000 Eggs in a Cocoon
A female raft spider lays up to 1,000 eggs twice a year and wraps them in a cocoon. At first, she carries it in her chelicerae. Shortly before the young hatch, she attaches it to plants on the bank with silk and guards it.
5 – True size
From leg tip to leg tip, the raft spider measures 5 cm.
Family
Pisauridae, nursery web spiders
Genus
Dolomedes, fishing spiders
Species
102
Worldwide
2
Central Europe
Of the 102 species worldwide, two occur in Central Europe: the raft spider (Dolomedes fimbriatus) and the great raft spider (Dolomedes plantarius). The peatlands at Piller Saddle, at more than 1,500 metres above sea level, are among the highest-altitude sites where the species occurs in Austria.
Distribution
Raft spiders occur almost worldwide. Their main distribution areas are Europe and Asia.
Threats and Conservation
Raft spiders are widespread in many regions, but they are nowhere common. Because their habitats have often been destroyed or drained, the species has become rarer. In Austria, however, it is currently considered not endangered.