Dark Fishing Spider, Dock Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae. Key family characteristics include similar-sized eyes, strong legs suited for running on water or vegetation, and carrying egg sacs in the chelicerae until near hatching.
Physical Description
Robust, large-bodied spider with a broad cephalothorax and elongated oval abdomen. The body is covered in fine, velvety hairs, giving it a muted, matte texture. Females are noticeably larger than males, a typical trait for the species.
Size Estimate
Body length ranges from 15 to 26 mm for females, with a leg span that can reach up to 70 to 90 mm, making it one of the largest spiders in its range. This specimen appears to be a mature or near-adult individual.
Coloration & Markings
Mottled grey, dark brown, and black coloration providing excellent camouflage against tree bark and rocky surfaces. The legs feature distinct dark bands and rings, and the abdomen often displays irregular chevron or W-shaped markings.
Web Type
Fishing spiders do not build webs to capture prey. Instead, they are active roaming hunters that wander across vertical surfaces, rocks, and vegetation near water sources.
Eye Arrangement
Eight eyes arranged in two distinct, slightly curved rows of four. The eyes are roughly equal in size and are positioned to give a broad field of vision for detecting movement from above and ahead.
Leg Characteristics
Long, powerful legs held out radially to the sides in a sprawling posture, similar to huntsman spiders. The legs feature prominent spines and dark banding, equipped with claws and scopulae for gripping smooth or wet surfaces.
Venom & Safety Information
Venom Information
Contains neurotoxic venom used primarily to subdue active invertebrate prey. The venom is specialized for arthropods and is generally not potent or dangerous to humans.
Medical Significance
Not medically significant. A bite from a dark fishing spider is rare and typically no more painful than a bee or wasp sting, usually resulting in localized swelling and redness that subsides quickly.
Safety Recommendations
Best admired from a distance. If found indoors, gently capture it using a container and a stiff card, then release it outdoors in a wooded area or near a garden. Avoid handling them bare-handed to prevent defensive bites.
Habitat & Behavior
Habitat & Range
Found throughout eastern North America, inhabiting wooded areas near streams, rivers, ponds, and lakes. Frequently found resting on tree trunks, wooden fences, and dock pilings, often some distance away from actual water.
Behavior & Temperament
Active nocturnal hunter, though occasionally seen basking during the day. Generally docile and non-aggressive towards humans, preferring to flee rapidly or drop to the ground when disturbed rather than bite.
Diet & Prey
Generalist predator feeding on large insects, other spiders, and occasionally small aquatic vertebrates such as small fish or tadpoles by detecting vibrations on the water surface.
Seasonal Activity
Most active from late spring through early autumn. Mating typically occurs in the warmer summer months, and adults overwinter in protected crevices under loose bark or in woodpiles.
Description
The dark fishing spider is a magnificent and formidable-looking arachnid often encountered on tree trunks or wooden structures near wooded wetlands. Despite its intimidating size and stealthy hunting prowess, it is a shy creature that plays a vital role in balancing riparian ecosystems.
Key Features
Large size, sprawling leg posture, distinctive dark banding on the legs, mottled grey-brown coloration with chevron markings, and lack of a traditional web.
Similar Species
Can be confused with wolf spiders (Lycosidae) or rabid wolf spiders (Rabidosa rabida). Fishing spiders can be distinguished by their sprawling leg posture and preference for elevated vertical surfaces like tree trunks rather than running directly on the ground.
Life Cycle
Females construct a spherical silken egg sac which they carry in their jaws until just before hatching, at which point they build a nursery web in vegetation and guard the spiderlings through their first molts.
Ecological Importance
Serves as an effective predator of various insect populations and small aquatic organisms, acting as an important link in the food web of riparian and forest habitats.
Conservation Status
Secure and widespread across its natural geographic range. Not currently evaluated by the IUCN, with stable populations benefiting from wetland and forest conservation efforts.
Interesting Facts
Despite their common name, dark fishing spiders are frequently found considerable distances away from water in dry upland forests. They are capable of walking on the water's surface and can even dive beneath the surface to escape predators or capture prey.
Photography Tips
Use a macro lens with a fast shutter speed to capture leg banding and eye arrangement details. Early morning or overcast conditions provide soft, even lighting without harsh shadows on their textured bodies.
Identified: 2026-08-07T17:57:07.716388