Dark Fishing Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae
Physical Description
A large, robust spider with a flattened body profile and densely hairy legs. The cephalothorax is broad with a distinct central groove, and the abdomen is elongated and slightly tapered at the rear. This specimen appears to be an adult or sub-adult based on its heavy build.
Size Estimate
Body length typically 15-26mm (females), with a total leg span reaching 75-100mm (3-4 inches). This individual appears large and mature.
Coloration & Markings
Mottled brown and grey camouflage pattern. The abdomen features prominent dark, W-shaped or chevron markings. The legs are marked with distinct dark and light banding, which is visible in the provided image.
Web Type
The Dark Fishing Spider is a hunting spider and does not build a web to catch prey. However, females construct a 'nursery web' of silk around their egg sac once the spiderlings begin to hatch.
Eye Arrangement
Eight eyes in two rows: the posterior row is slightly curved with larger eyes, and the anterior row is straight. This provides excellent motion detection for active hunting.
Leg Characteristics
Long, thick legs covered in sensory hairs and spines. The legs are held in a wide, sprawling posture, allowing the spider to distribute its weight across surfaces, including water.
Venom & Safety Information
Venom Information
Possesses a complex venom primarily containing neurotoxins designed to paralyze insects. It is not considered dangerous to humans or pets.
Medical Significance
Low medical significance. The bite is often compared to a bee sting, causing localized pain, redness, and minor swelling. It only bites if handled roughly or pinned against the skin.
Safety Recommendations
If found indoors, use the 'cup and cardboard' method to relocate the spider outside to a tree or wooded area. Do not handle with bare hands to avoid a defensive bite.
Habitat & Behavior
Habitat & Range
Common throughout the Eastern and Central United States and Southeastern Canada. Unlike other fishing spiders, 'D. tenebrosus' is often found far from water in wooded areas, on tree trunks, or inside basements and sheds.
Behavior & Temperament
A fast, nocturnal ambush hunter. They are generally timid and flee from humans, but can move with startling speed. They primarily hunt on vertical surfaces like tree trunks.
Diet & Prey
Opportunistic hunters of large insects (crickets, moths, beetles). While they can catch small fish or tadpoles if near water, their diet is primarily terrestrial insects.
Seasonal Activity
Most active from late spring through late summer. Adults are commonly found indoors or on porches in the autumn as they seek shelter.
Description
The Dark Fishing Spider is one of the largest spiders in North America. Its impressive size and leg span often cause alarm, but it is a beneficial predator and a master of camouflage, blending perfectly against weathered wood and tree bark.
Key Features
Distinguished by its massive size, banded legs, and the W-shaped chevron patterns on the abdomen. Unlike wolf spiders, fishing spiders tend to be more sprawling and have different eye arrangements.
Similar Species
Often confused with Wolf Spiders (Lycosidae), but can be distinguished by the eye pattern and the lack of a single large pair of posterior median eyes. It also resembles the smaller Dolomedes scriptus.
Life Cycle
Females carry their large, spherical egg sacs in their chelicerae until the eggs are ready to hatch. They then build a nursery web in vegetation, guard the sac, and stay with the spiderlings for several days.
Ecological Importance
Crucial nocturnal predator that helps control populations of large forest insects. They serve as a food source for birds, lizards, and larger mammals.
Conservation Status
Not evaluated by IUCN, but currently widespread and common across its range with no significant threats noted.
Interesting Facts
Despite their name, Dark Fishing Spiders are the most terrestrial of the fishing spiders. They can run across the surface of water by utilizing surface tension and can even dive beneath the surface if threatened.
Photography Tips
Focus on the dorsal (top) pattern of the abdomen and the banding on the legs. Using a diffused flash helps bring out the subtle brown and grey gradients of their camouflage.
Identified: 2026-07-08T22:30:16.444967