Dark Fishing Spider, Dock Spider, Wharf Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae
Physical Description
Robust, elongated body with a slightly flattened cephalothorax and an oval-to-elongated abdomen. Covered in fine, velvety hair that provides camouflage against wood and bark.
Size Estimate
Body length ranges from 15 to 26 mm for females (males are smaller, around 7 to 13 mm) with a leg span reaching up to 70 to 90 mm. The specimen appears to be an adult or sub-adult.
Coloration & Markings
Mottled brown, gray, and dark olive coloration with distinctive dark, W-shaped or chevron markings across the legs and abdomen, blending seamlessly into textured wooden surfaces.
Web Type
Fishing spiders do not build webs to capture prey; instead, they are active nocturnal or crepuscular hunters that patrol surfaces or water edges.
Eye Arrangement
Eight small-to-medium eyes arranged in two distinct curved rows, typical of the Pisauridae family, providing good forward vision to detect movement.
Leg Characteristics
Long, powerful legs spread outward in a sprawling crab-like posture. They feature distinct dark and light banding, strong spines, and specialized claws for gripping surfaces and walking on water.
Venom & Safety Information
Venom Information
Neurotoxic and proteolytic venom used primarily to subdue active prey. While potent to insects, it is generally harmless to humans.
Medical Significance
Not medically significant. A bite is rare and typically results in minor, localized pain, swelling, and redness comparable to a bee sting, subsiding within a day.
Safety Recommendations
Admire from a safe distance. If found on a deck or home, it can be gently relocated using a container and a piece of card without needing pest control.
Habitat & Behavior
Habitat & Range
Found across eastern North America, inhabiting wooded areas near streams, ponds, lakes, and human structures such as wooden decks, docks, sheds, and tree trunks.
Behavior & Temperament
Active ambush and pursuit hunter. Generally timid, preferring to flee or hide when disturbed rather than bite, though females guarding nursery webs can show defensive postures.
Diet & Prey
Carnivorous; feeds on a variety of insects, aquatic invertebrates, small fish, and occasionally tadpoles by detecting surface ripples.
Seasonal Activity
Most active from late spring through early autumn, mating during the warmer summer months and overwintering under loose bark or in sheltered crevices.
Description
The Dark Fishing Spider is an impressive yet harmless giant often encountered on wooden docks, fences, and tree trunks near water. With its sprawling posture and mottled camouflage, it is an expert predator of both land and water.
Key Features
Large size, sprawling leg posture, distinctive chevron or W-shaped markings on the legs and abdomen, and a preference for vertical wooden surfaces near water.
Similar Species
Wolf spiders (Lycosidae) and other fishing spider species like Dolomedes scriptus. Wolf spiders often carry egg sacs attached to their spinnerets rather than in their jaws.
Life Cycle
Females construct a spherical silken egg sac carried in their jaws. Before hatching, she builds a nursery web in vegetation, guarding the spiderlings through their early molts.
Ecological Importance
Acts as an effective natural pest controller, keeping insect populations in check while serving as an important food source for birds, amphibians, and mammals.
Conservation Status
Secure and widespread throughout its native range with stable population trends, currently facing no major conservation threats.
Interesting Facts
Despite their name, dark fishing spiders can travel across the surface of the water using surface tension and can even submerge themselves briefly to escape predators.
Photography Tips
Approach slowly to avoid startling it. Use a macro lens from a low angle to capture the facial features and leg banding clearly, ideally in natural diffused lighting.
Identified: 2026-10-02T23:41:06.288738