What is "raft spider"

Water spider \Wa"ter spi"der\ (Zo["o]l.)

1. An aquatic European spider ( Argyoneta aquatica) which constructs its web beneath the surface of the water on water plants. It lives in a bell-shaped structure of silk, open beneath like a diving bell, and filled with air which the spider carries down in the form of small bubbles attached one at a time to the spinnerets and hind feet. Called also diving spider.

2. A water mite.

3. Any spider that habitually lives on or about the water, especially the large American species ( Dolomedes lanceolatus) which runs rapidly on the surface of water; -- called also raft spider.

The raft spider, also known as the Jesus 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, and derives its name from its ability to walk on water.

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 the type species of its genus.

The female's body measures up to long with a leg span of about ; 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.