Dark Fishing Spider, Dock Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae. Key family characteristics include similar-sized eyes in two rows and the female's habit of carrying her egg sac in her chelicerae until just before hatching.
Physical Description
Large, robust body with a somewhat flattened appearance. The cephalothorax is broad and rounded, while the abdomen is elongated and oval. The texture appears velvety due to a dense covering of fine, short hairs. Sexual dimorphism is pronounced, with females being significantly larger than males.
Size Estimate
Body length ranges from 15 to 26 mm for females and 7 to 13 mm for males, with a substantial leg span that can reach up to 70 to 90 mm or more, making it one of the largest spiders in its range.
Coloration & Markings
Mottled patterns of brown, gray, and black, providing excellent camouflage against tree bark and wooden structures. The legs display distinct dark banding. Some individuals may feature lighter W-shaped markings on the abdomen.
Web Type
Does not build a web to catch prey. They are active hunters that wander freely, though females construct a temporary silk nursery web for their egg sacs when ready to hatch.
Eye Arrangement
Eight small, dark eyes arranged in two distinct, slightly curved rows of four. The anterior and posterior rows are roughly equal in width, typical of the family Pisauridae.
Leg Characteristics
Long, powerful legs held out laterally in a sprawling crab-like or wolf spider-like posture. The legs are covered in fine spines and feature clear dark bands. They are specialized for rapid movement across surfaces and water.
Venom & Safety Information
Venom Information
Neurotoxic and cytotoxic venom designed primarily to immobilize invertebrate prey. It is not considered dangerous or medically significant to humans.
Medical Significance
Harmless to humans. A bite may cause minor local pain, swelling, and redness similar to a bee or wasp sting, but envenomations are rare as they prefer to escape when cornered.
Safety Recommendations
No special safety measures are necessary. If found indoors, they can be safely gently guided into a container and relocated outside. Wear gloves if handling.
Habitat & Behavior
Habitat & Range
Found throughout eastern and central North America. Prefers wooded areas near streams, ponds, and swamps, but frequently ventures onto vertical surfaces like tree trunks, wooden fences, and the siding of rural buildings.
Behavior & Temperament
Nocturnal and crepuscular hunter. Rather than building webs, it relies on ambush or active stalking. When disturbed, it typically flees rapidly or drops to the ground rather than displaying aggression toward humans.
Diet & Prey
Primarily feeds on large insects, other spiders, and occasionally small aquatic organisms such as tadpoles and small fish, which it catches by sitting at the water's edge with its front legs resting on the surface.
Seasonal Activity
Most active from late spring through early autumn. They overwinter as juveniles or sub-adults under loose bark, in logs, or inside sheltered structures.
Description
The Dark Fishing Spider is an impressive giant of the woodlands and wetlands. With its long, banded legs and mottled camouflage, it blends seamlessly into tree bark or rustic wooden walls. Though large and intimidating, it is a shy, beneficial hunter that helps control insect populations.
Key Features
Large size, long banded legs, sprawling resting posture on vertical surfaces, mottled brown and gray coloration, and the absence of a prey-capturing web.
Similar Species
Wolf spiders (Family Lycosidae), which carry egg sacs attached to their spinnerets rather than in their jaws, and sometimes large funnel-web weavers.
Life Cycle
Mating occurs in spring or early summer. Females carry a spherical silk egg sac in their jaws. Before hatching, she attaches the sac to vegetation and builds a tent-like nursery web, guarding it until the spiderlings disperse after their first molt.
Ecological Importance
Acts as an effective predator of insects and other arthropods, playing an important role in balancing local food webs in both terrestrial and semi-aquatic habitats.
Conservation Status
Not threatened or endangered; populations are stable and widespread throughout their natural geographic range.
Interesting Facts
Despite the name 'fishing spider,' many individuals live far from water on forest trees and wooden structures. They can skate across the water surface and even submerge themselves briefly to escape predators.
Photography Tips
Approach slowly to avoid startling them into fleeing. Use a macro lens from a safe lateral angle, ensuring good natural lighting or a diffused flash to highlight the intricate leg banding and body textures.
Identified: 2026-08-07T17:55:18.080137