Dark Fishing Spider
Dolomedes tenebrosus
Family Pisauridae (Nursery Web Spiders), Order Araneae
Physical Description
A large, robust spider with a flattened body profile adapted for hugging surfaces. The cephalothorax and abdomen are hairy with a mottled appearance. The abdomen is slightly tapered at the rear. Female specimens are significantly larger and bulkier than males.
Size Estimate
Body length typically 15-26mm for females; leg span can reach 3-4 inches (75-100mm). This appears to be a mature or near-mature individual.
Coloration & Markings
Primary colors are shades of grey, brown, and black. Distinguished by three or four prominent dark W-shaped or chevron-like markings on the dorsal side of the abdomen, followed by smaller chevrons toward the rear. The legs are notably banded with alternating light and dark rings.
Web Type
Non-web-building hunter. They do not use webs to catch prey but females build 'nursery webs' to protect their egg sacs just before the spiderlings hatch.
Eye Arrangement
Eight eyes arranged in two rows. The posterior row is slightly recurved (curving backward) and contains larger eyes than the anterior row, providing excellent vision for hunting.
Leg Characteristics
Long, thick, and powerful legs covered in fine hairs and prominent spines. The legs are held in a wide, sprawling posture, which helps distribute weight and facilitates rapid movement across vertical surfaces or water.
Venom & Safety Information
Venom Information
Contains complex proteins designed to immobilize insect prey. The venom is not considered medically significant to healthy humans, often compared to a bee or wasp sting in terms of potency.
Medical Significance
Low danger level. Bites are rare and usually result in localized pain, redness, and minor swelling. Symptoms typically subside within a few hours. No specific medical treatment is usually required unless an allergic reaction occurs.
Safety Recommendations
If found indoors, they can be easily relocated by placing a large container over them and sliding a stiff piece of cardboard underneath. They are harmless to the structure of the home and do not infest.
Habitat & Behavior
Habitat & Range
Native to North America, ranging from Southern Canada through the Eastern and Central United States. Unlike other fishing spiders, this species is often found far from water in wooded areas, on tree trunks, and frequently inside structures like sheds, basements, or garages.
Behavior & Temperament
An active nocturnal ambush hunter. They are generally shy and will vanish quickly when disturbed. While they appear intimidating due to their large size, they are not aggressive toward humans and typically only bite if handled roughly or pinned.
Diet & Prey
Feeds on various large insects, including crickets, moths, and cockroaches. When near water, they can occasionally take small fish or tadpoles, though they are more terrestrial than other Dolomedes species.
Seasonal Activity
Most active from late spring through late summer. Adults are frequently seen in June and July during the breeding season. They may overwinter in developmental stages under bark or in crevices.
Description
The Dark Fishing Spider is one of the largest spiders in its range, often startling homeowners with its size and 'hairy' appearance. It is a master of camouflage, blending perfectly against tree bark or weathered wood. Despite its name, it is a frequent visitor of dry, wooded habitats.
Key Features
Large size, distinct W-shaped abdominal patterns, and heavy dark-and-light banding on the legs. Spindly but powerful leg configuration.
Similar Species
Commonly confused with Wolf Spiders (Lycosidae), but identified by the W-shaped markings and eye arrangement. Also similar to other Dolomedes species like D. triton, which has white spots and stays closer to water.
Life Cycle
Females carry their large, globular egg sacs in their chelicerae (mouthparts). Before the spiders hatch, the mother builds a silk nursery in foliage and guards it. Spiderlings may disperse via ballooning. Lifespan is approximately 1-2 years.
Ecological Importance
Highly beneficial as a natural pest control agent. They consume a large volume of forest floor and household pests, and serve as a significant food source for birds, lizards, and larger mammals.
Conservation Status
Not evaluated (Stable). Generally common throughout its range with no major threats.
Interesting Facts
They can 'skate' across the surface of water using surface tension and can even dive beneath the surface to escape predators, breathing through a thin layer of air trapped in their body hairs.
Photography Tips
Use a side-angle to capture the sprawling leg posture and a top-down (dorsal) shot to clearly document the W-shaped markings and eye arrangement for positive identification.
Identified: 2026-05-27T03:31:29.361873