any member of a family of spiders (order Araneida) noted for the female spider's habit of making a protective nursery web for the young and standing guard over that web. Most species are medium to large in size, and many are found near the water. Members of the genus Dolomedes, the most common North American genus, sometimes have a leg spread of 7.5 cm (3 inches).

The female spider carries her egg sac, which contains a few hundred eggs, in her mouthparts until the young spiders are almost ready to emerge. She then attaches the sac to a plant, ties leaves around it with silk, and remains to guard the young from predators.