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, when she builds a nursery web.
Physical Description
Large, robust body with a flattened carapace and an elongate oval abdomen. The texture is velvety due to a dense covering of fine, short setae. They exhibit noticeable sexual dimorphism, 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 formidable leg span that can reach up to 70 to 90 mm or more. This specimen appears to be a mature or nearly mature adult.
Coloration & Markings
Mottled patterns of gray, brown, black, and white providing exceptional camouflage against tree bark. The abdomen typically features distinct dark chevron markings pointing backwards, while the cephalothorax has lighter margins and complex geometric patterns.
Web Type
Does not build a web to catch prey. Instead, they are active wandering hunters that rely on stealth, speed, and vibrations to capture prey.
Eye Arrangement
Eight eyes arranged in two distinct rows of four. The eyes are all dark and roughly similar in size, distinguishing them from wolf spiders which have a prominent pair of larger posterior median eyes.
Leg Characteristics
Long, powerful legs spread outward in a sprawling, crab-like stance that maximizes surface contact and vibration detection on bark or water surfaces. The legs are strongly banded with dark rings and equipped with prominent spines and scopulate hairs.
Venom & Safety Information
Venom Information
Contains neurotoxic and proteolytic components tailored for subduing invertebrate prey. Their venom is generally not considered medically significant to humans.
Medical Significance
Harmless to humans. A bite may cause localized pain, redness, and swelling similar to a bee or wasp sting, but they are reluctant biters and prefer to escape.
Safety Recommendations
No special safety measures are required. If found inside a home, they can be easily relocated outdoors using a container and a piece of cardboard. Avoid handling them bare-handed to prevent accidental defensive bites.
Habitat & Behavior
Habitat & Range
Found throughout eastern North America, ranging from Canada down to Florida and west to Texas. Despite being called fishing spiders, they are frequently found far from water on tree trunks, wooden fences, and stone walls in wooded environments.
Behavior & Temperament
Nocturnal or crepuscular hunters that spend daylight hours flattened against tree trunks or vertical surfaces where their camouflage renders them nearly invisible. They are generally docile and will flee rapidly when disturbed, though females guarding a nursery web may display defensive postures.
Diet & Prey
Generalist predators consuming a wide variety of insects, other spiders, and occasionally small aquatic vertebrates such as tadpoles and small fish by sensing ripples on the water's surface.
Seasonal Activity
Most active from late spring through autumn. They overwinter as juveniles or sub-adults hidden beneath loose tree bark, in rotting logs, or in sheltered crevices.
Description
The Dark Fishing Spider is a magnificent master of camouflage, frequently encountered spread-eagled against the rough bark of a tree. As one of the largest spiders in its range, its sprawling stance and intricate patterned markings command attention while providing near-perfect concealment from predators and prey alike.
Key Features
Large size, sprawling leg posture, distinctive dark chevron markings on the abdomen, mottled gray and brown coloration, and eight similarly sized eyes arranged in two rows.
Similar Species
Wolf spiders (Family Lycosidae) and other fishing spider species like Dolomedes albineus. Wolf spiders can be distinguished by their prominent large pair of eyes on the upper face, while other Dolomedes species often inhabit different microhabitats or possess subtly different carapace markings.
Life Cycle
Females construct large spherical silk egg sacs which they carry in their jaws. Near hatching time, they attach the sac to vegetation and spin a protective nursery web around it, standing guard until the spiderlings disperse after their first molt. Lifespan typically spans up to two years.
Ecological Importance
Acts as an important apex invertebrate predator in both terrestrial and semi-aquatic ecosystems, helping to regulate insect populations and serving as a food source for birds, amphibians, and small mammals.
Conservation Status
Not evaluated by the IUCN, but populations are generally stable and widespread throughout their native geographic range.
Interesting Facts
Despite their common name, many individuals live entirely terrestrial lives far away from any water source. They are capable of walking across the surface of the water and can even dive beneath the surface to escape predators or hunt.
Photography Tips
Photograph from a parallel angle to the tree trunk to keep the entire spider within the focal plane. Use natural side lighting or a diffused flash to highlight the intricate textures and chevron patterns without creating harsh shadows.
Identified: 2026-08-18T00:10:30.207525