Dark Fishing Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae
Physical Description
Large, flattened spider with a robust cephalothorax and a tapering abdomen. The body is covered in fine, velvety hairs and short spines especially on the legs. Distinctive W-shaped or chevron patterns are often visible on the dorsal abdomen.
Size Estimate
Body length 15-26mm for females; leg span can reach 75-100mm (3-4 inches). This is a large adult female specimen.
Coloration & Markings
Mottled brown, grey, and black patterns providing excellent camouflage against tree bark. Legs are prominently banded with alternating dark and light rings. The carapace features a paler U-shaped central area.
Web Type
The Dark Fishing Spider does not build a web to catch prey; it is an active ambush hunter. However, females build 'nursery webs' to protect their spiderlings after the egg sac begins to hatch.
Eye Arrangement
Eight eyes arranged in two rows. The bottom row is slightly curved, and the posterior eyes are larger and positioned to provide a wide field of view for hunting.
Leg Characteristics
Long, thick, powerful legs held in a flattened, wide posture. Distinctive dark and light banding (annulations) and prominent black spines (macrosetae) used for gripping prey and climbing.
Venom & Safety Information
Venom Information
Possesses a complex venom used to paralyze prey. It is not considered medically significant to healthy humans, though it contains necrotizing enzymes in very low quantities.
Medical Significance
Low danger level. A bite may cause localized pain, redness, and swelling similar to a bee sting, but symptoms usually subside within hours. Seek medical attention only if an allergic reaction occurs.
Safety Recommendations
Relocate using the 'cup and paper' method if found indoors. They are fast but will not bite unless pinched or handled roughly. Wear gloves when moving woodpiles where they may be hiding.
Habitat & Behavior
Habitat & Range
Common across Eastern North America. Unlike other 'fishing spiders,' D. tenebrosus is often found far from water in wooded areas, on tree trunks, and occasionally inside basements or sheds.
Behavior & Temperament
A shy, nocturnal ambush hunter. They are incredibly fast and agile. While they are large and look intimidating, they are generally non-aggressive and prefer to flee or remain motionless to blend into their surroundings.
Diet & Prey
Generalist predators feeding on large insects, other spiders, and occasionally small vertebrates like tadpoles or tiny fish if near water. They hunt by sensing vibrations through their legs.
Seasonal Activity
Most active from late spring through late summer. Mating occurs in early summer, and large individuals are most frequently spotted by homeowners in the fall as they seek overwintering sites.
Description
An impressive and large arachnid, the Dark Fishing Spider is a master of camouflage. Often mistaken for a Wolf Spider due to its size, it is a key woodland predator that relies on speed rather than silk to secure its meals.
Key Features
Large size, heavily banded legs, W-shaped abdominal markings, and the absence of a capture web. Distinguished from Wolf Spiders by eye arrangement and the lack of a single large pair of anterior-facing eyes.
Similar Species
Dolomedes scriptus (usually found closer to water with more distinct white markings) and various Wolf Spiders (Lycosidae family, which have a different eye pattern and carry egg sacs on spinnerets).
Life Cycle
Females carry their large, spherical egg sacs in their chelicerae until the spiderlings are ready to emerge. They then construct a nursery web in foliage. Lifespan is approximately 1-2 years.
Ecological Importance
Significant apex invertebrate predator in woodland and riparian ecosystems. They provide natural pest control for large insects like crickets and cockroaches.
Conservation Status
Common and widespread; not currently listed on the IUCN Red List or under any specific conservation threat.
Interesting Facts
Despite their name, this specific species is frequently found in dry woods. They can run across the surface of water using surface tension and can even dive beneath the surface to escape predators.
Photography Tips
Focus on the eyes and the pattern on the cephalothorax for identification. Use a side-view or top-down macro shot to capture the banding on the legs and the abdominal chevrons.
Identified: 2026-07-15T13:11:14.499041