Diagnostic characters
- Female carries the egg sac in her chelicerae, held beneath the body
- Nursery tent of silk built in vegetation shortly before eggs hatch
- Dolomedes have pale lateral bands along the carapace and banded legs
- Rests at the water margin with front legs on the surface film
- Can run across water and submerge for extended periods, carrying an air film
Habitat and seasonality
Pond and stream margins, docks, emergent vegetation, wet woodland, and occasionally dry meadow in Pisaurina.
Adults conspicuous late spring through late summer; nursery tents are most visible in midsummer.
Medical significance
Low. Large size makes a defensive bite painful, but there are no systemic or necrotic effects.
Surface-film predation
Dolomedes detects prey by reading ripples in the water surface with the tarsal organs of the front legs, then runs across the film to strike. Documented prey includes aquatic insects, tadpoles, and small fish up to several times the spider's mass. When threatened the spider descends a plant stem below the surface, held down by its grip and insulated by a film of trapped air.
Nursery construction
Shortly before eggs hatch the female fixes the sac among leaves, spins a dense tent of silk around it, and stands guard on the outside until the spiderlings disperse. This behavior is the source of the family's common name and is the clearest field character separating Pisauridae from Lycosidae.
Families most often confused with Pisauridae
| Family | How to separate it |
|---|---|
| Lycosidae | Wolf spiders attach the egg sac to the spinnerets and have two enlarged posterior median eyes |
| Sparassidae | Huntsman spiders hold legs laterigrade and lack the aquatic association |
References
- [1]World Spider Catalog, version 26 - Natural History Museum Bern. Accessed 2026-06-14.
- [2]Spiders of North America: An Identification Manual, 2nd ed. - American Arachnological Society. Accessed 2026-06-14.
- [3]Common Spiders of North America - University of California Press. Accessed 2026-06-14.