Brownish-Gray Fishing Spider

Brownish-Gray Fishing Spider ( Dolomedes tenebrosus )

The brownish-gray fishing spider, Dolomedes tenebrosus, is often found near or in water, but they also hunt in forests.  Dolomedes do not build webs to capture prey.  They roam freely and consume a variety of animals in and on water and on land.  They can run across the surface of a pool or stream and actually dive and remain submerged for several minutes while they hunt and capture small fish and tadpoles using sharp claws and powerful fangs.  The brown fishing spider is able to deliver a memorable bite.  The abdomen has a series of black ‘W’-shaped markings on posterior half and unique pattern on the front half that somewhat resembles the face of an ant.


Unlike wolf spiders, which they resemble in their giant size, they typically live near water.  They run freely over water in pursuit of prey, including small fish and aquatic insects.  When frightened, they may dive beneath the surface.  Dolomedes tenebrosus are opportunistic, generalist feeders.  Usual habitats for D. tenebrosus are swamp, pond, and lake margins, where it may be found on tree trunks, rocks, logs, and similar situations.

I photographed this spider on a white oak tree in an area of mature, steep slope forested hardwoods and swamp along Western Run, in Upper Marlboro, Prince George’s County, MD.  The spider was quite large, with a spread about the size of a peanut butter or mayonnaise jar lid.