Dark Fishing Spider, Dock Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae. Key family characteristics include similar-sized claws, large eyes arranged in two rows, and carrying egg sacs with their chelicerae until just before hatching.
Physical Description
Robust, large body with a longer abdomen than cephalothorax, covered in fine velvety hairs. Females are significantly larger than males, showing pronounced sexual dimorphism typical of large fishing spiders.
Size Estimate
Body length ranges from 15 to 26 mm for females, with a massive leg span reaching up to 70 to 90 mm or more, making it one of the largest spiders in its range.
Coloration & Markings
Mottled grey, brown, and black coloration providing excellent camouflage against tree bark and wood. Features distinct dark W-shaped or chevron markings along the dorsal abdomen and alternating light and dark banding on the legs.
Web Type
Does not build a traditional web to catch prey. Instead, nursery web spiders roam freely or wait along vertical surfaces and water edges, though females construct a silken nursery web in vegetation for their egg sacs.
Eye Arrangement
Eight eyes arranged in two curved rows of four, set closely together on the upper part of the face, with the posterior row slightly wider.
Leg Characteristics
Long, powerful legs featuring prominent spination and distinct dark banding. They are held sprawled outward to maximize surface vibrations.
Venom & Safety Information
Venom Information
Contains neurotoxic and proteolytic components used primarily to subdue invertebrate prey. Not specialized for defense against large mammals.
Medical Significance
Harmless to humans. A bite may cause localized pain, redness, and minor swelling comparable to a bee sting, but it is not medically significant.
Safety Recommendations
Observe from a distance. If found indoors, gently guide the spider into a container using a piece of cardstock and release it outdoors in a suitable woodland habitat.
Habitat & Behavior
Habitat & Range
Found across eastern North America, typically inhabiting wooded areas near streams, ponds, swamps, and tree trunks, frequently venturing onto building siding and docks.
Behavior & Temperament
Active nocturnal or crepuscular hunters. They are generally non-aggressive toward humans, preferring to flee or hide, but brooding females defending nursery webs can be defensive.
Diet & Prey
Primarily feeds on large insects, other spiders, and occasionally small aquatic vertebrates such as tadpoles and small fish by sensing surface ripples on water.
Seasonal Activity
Most active from late spring through early autumn, mating in warmer months and overwintering under loose bark or in sheltered crevices.
Description
The Dark Fishing Spider is an impressive giant of the forest floor and tree trunks. With its velvety grey-brown coat and striking leg bands, it blends seamlessly into bark. Despite its formidable size and ability to walk on water, it is a shy creature that plays a vital role in wetland and woodland ecosystems.
Key Features
Large size, dark chevron markings on a mottled grey-brown abdomen, prominent leg banding, and a strong preference for vertical tree trunks or structures near water.
Similar Species
Wolf spiders (Lycosidae), which carry their egg sacs attached to their spinnerets rather than in their jaws, and other Dolomedes species like Dolomedes scriptus.
Life Cycle
Mating occurs in spring. Females produce a large spherical silk egg sac, carrying it in their jaws before constructing a tent-like nursery web in foliage. Spiderlings disperse via ballooning.
Ecological Importance
Serves as an effective top-tier invertebrate predator, helping regulate insect populations and acting as a food source for birds, amphibians, and small mammals.
Conservation Status
Common and widespread throughout its native range with stable populations; currently evaluated as Least Concern.
Interesting Facts
Despite being called fishing spiders, they are frequently found far from water on dry trees and house walls, using their vast leg span to detect airborne vibrations.
Photography Tips
Photograph in natural indirect light using a macro lens from a low angle to highlight the eye arrangement and detailed leg spination without startling the spider.
Identified: 2026-08-03T03:17:13.392347