Overview

Brief Summary

Biology

Although this species is widely known as the 'raft spider' in Britain, it does not make rafts. It is more appropriately called the fishing spider in Europe, as it hunts by sitting on vegetation next to pools of water, characteristically with the first two pairs of legs held together at an angle and resting on the surface of the water. This allows it to sense the presence of tadpoles, insects and even small fish, which it hauls out of the water. This species also hunts on land amongst vegetation, and on moss (3). The raft spider is able to crawl down water plants if threatened, and can remain below water for around an hour (3). During courtship, males signal to females by making regular surface waves on the water by jerking their abdomen up and down, and waving their legs in the air in a characteristic fashion. Females are very aggressive towards males, and in some cases they eat prospective mates (5). Female spiders belonging to this family make very large egg sacs, which they carry around beneath their body. When the time for the spiderlings to emerge approaches, the female deposits the egg sac on a leaf and spins a protective silk 'nursery web' around it. She then opens the egg sac slightly, and stands guard over it until the spiderlings emerge (3).
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Description

This large brown and white spider has long, sturdy legs and an oval-shaped abdomen. There are striking pale stripes along the sides of both the carapace and the abdomen (3). These stripes are due in part to a row of white hairs (2). Males are similar in appearance to females, although they have smaller abdomens (3).
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Distribution

Range

This spider has a wide but somewhat patchy range in Britain and is widespread in northern Europe (3).
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Ecology

Habitat

Found in damp, swampy habitats, with patches of water (3), and is especially associated with Sphagnum bogs (4).
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Dolomedes fimbriatus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 7
Species With Barcodes: 1
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Conservation

Conservation Status

Status

This widespread species is not threatened. It is not listed under any conservation designations (3).
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Threats

This species is not threatened.
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Management

Conservation

Conservation action has not been targeted at this widespread species.
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Wikipedia

Raft spider

The raft spider, Dolomedes fimbriatus, is a European spider of the family Pisauridae. The raft spider is one of the two largest spiders in the United Kingdom.

Like other Dolomedes spiders it hunts by running on the surface of water, and can submerge altogether to hide from predators.

It was described in chapter 5 of the book Svenska Spindlar by the Swedish arachnologist and entomologist Carl Alexander Clerck. It is th type species of its genus.

The female's body measures up to 22 millimetres (0.87 in) long with a leg span of about 70 mm (2.8 in); as with most spiders the male is considerably smaller.

Raft spiders are semi-aquatic and live around acidic bogs and in wet acidic grassland, especially where there are small pools of water. They are dark chocolate brown in colour (or sometimes greenish) with a conspicuous white or cream stripe along each side. The closely related great raft spider (Dolomedes plantarius) is similar in size, habits and appearance, but lives in fens.

Female raft spider carrying her egg sack

References[edit]

Further reading[edit]

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