Dolomedes is a large species of nursery web spiders known as fishing spiders, raft spiders, dock spiders or wharf spiders. There are more than 100 currently recognized species worldwide, 8 species in North America north of Mexico. Four species have been recorded in Minnesota.
Fishing spiders have a worldwide distribution, occurring on every continent except Antarctica. They are usually found near permanent bodies of water, or on floating vegetation in a body of water. Some are found in grassy meadows. One, dark fishing spider, wanders well away from water. One, white-banded fishing spider, lives in trees. The remainder are semiaquatic, spending part of their time in or on water.
Some fishing spiders sit quietly at the edge of a lake or pond or on floating vegetation. They rest their front three pairs of legs on the water surface to detect ripples or vibrations of prey. Others stalk prey on land. They eat mostly aquatic insects but also small fish. None hunt from webs, but all make nursery webs for their young.
All fishing spiders are covered with water repelling (hydrophobic) hairs. They are able to run across the surface of the water and even to “climb” under the surface to subdue prey. When they submerge, air is trapped on the underside of their abdomen, and they are able to breath underwater.