Is the dark fishing spider dangerous?

The dark fishing spider is harmless to people. Harmless. A bite from a large individual can hurt briefly, similar to a bee sting, with no lasting effect. It flees from people.

How do you identify a dark fishing spider?

Very large and distinctly flattened, with legs held out sideways. Dark W-shaped or chevron markings on the abdomen and strongly banded legs.

Where do dark fishing spiders live?

The dark fishing spider is found across most of the United States, in habitats including water, woods, indoors and basement.

Dark Fishing Spider

Harmless

Dolomedes tenebrosus · also called dock spider, wharf spider, raft spider

The dark fishing spider is the enormous flat spider found on tree trunks, dock pilings and — alarmingly for the householder — occasionally on a bathroom wall. It can walk on water and dive beneath the surface to catch small fish and tadpoles. Despite its size it is harmless, and unlike most fishing spiders it is often found well away from water.

Bite risk: Harmless. A bite from a large individual can hurt briefly, similar to a bee sting, with no lasting effect. It flees from people.
Size: Body 15–26 mm. One of the largest spiders in the eastern US — legspan can reach three inches or more.
Appearance: Large, flattened and mottled grey-brown with dark chevrons pointing forward on the abdomen and boldly banded legs. Legs are held out flat rather than tucked under.
Web: No catching web. Builds a nursery web for the young, hence the family name.
Found in: water, woods, indoors, basement
Family: Pisauridae
Range: Most of the United States

How to identify a dark fishing spider

Very large and distinctly flattened, with legs held out sideways.
Dark W-shaped or chevron markings on the abdomen and strongly banded legs.
No web.
Often on tree trunks, decking or dock structures near water.

How it behaves

Sits motionless on a vertical surface or at the water's edge with front legs resting on the surface film, detecting ripples. Runs on water and can submerge.

What the dark fishing spider is confused with

One observation settles each of these.

Wolf spider →

Wolf spiders are stockier with a domed body and two huge forward eyes. Fishing spiders are flat with legs held out sideways and eyes in two rows.

Nursery web spider →

Nursery web spiders are slimmer with a lengthwise stripe rather than chevrons.

If you think you were bitten

Most suspected spider bites are not spider bites. Studies of patients presenting with a “spider bite” repeatedly find that the large majority are bacterial skin infections — frequently MRSA — which need antibiotics rather than reassurance. A spreading, painful, pus-filled sore is far more likely to be an infection than a spider.
Wash it, ice it, and watch it. Clean the area with soap and water, apply a cold pack, and keep an eye on it.
Get medical care if the wound spreads or darkens, if you develop cramping, sweating, fever or severe abdominal pain, or if you are confident it was a widow or a recluse.
Bring the spider only if it is already dead and to hand. Do not go looking for it. Doctors treat symptoms, not species.

In the US, the Poison Help line is 1-800-222-1222. This site is a reference, not medical advice.

Not sure it was a dark fishing spider? Identify it step by step →