Dark Fishing Spider
Dolomedes tenebrosus (likely candidate based on markings, proportion, and leg banding)
Pisauridae (Nursery Web Spiders), Order Araneae
Physical Description
Flattened, robust body shape typical of semi-aquatic or tree-dwelling ambush hunters. The carapace features a central dark area bordered by lighter gray-brown bands. The abdomen is oval with faint light and dark mottling and subtle chevron pattern traits. Legs are relatively long, stout, and densely covered in fine setae.
Size Estimate
Estimated body length around 15-25 mm for females (smaller for males), with a leg span potentially reaching 50-75 mm (2-3 inches). The specimen appears curl-legged or stressed, making exact measurement approximate.
Coloration & Markings
Mottled brown, gray, and black camouflage pattern. Distinct dark transverse bands/stripes run across all eight legs. The carapace shows dark brown to black longitudinal markings surrounded by tan/gray highlights, designed for blending against tree bark or rocks.
Web Type
Does not spin a web for prey capture. Females spin silken egg sacs which they carry in their chelicerae, later constructing a nursery web among foliage to protect newly hatched spiderlings.
Eye Arrangement
8 eyes arranged in two curved rows (a lower row of four small eyes and an upper row of four larger, prominent eyes forming a slight W or curved pattern), providing wide field of vision for active hunting.
Leg Characteristics
Long, thick, power-packed legs with prominent dark and light brown/gray ringed bands. Equipped with dense scopulae (hairs) allowing them to walk easily on textured vertical surfaces or skim across water film.
Venom & Safety Information
Venom Information
Contains mild cytotoxic/neurotoxic venom intended for paralyzing small insect prey. Venom is low potency for humans and not considered medically dangerous.
Medical Significance
Not medically significant. Bites are extremely rare and usually only occur if trapped tightly against skin. Symptoms resemble a mild bee or wasp sting (localized swelling, mild pain, and redness).
Safety Recommendations
No extermination needed. If found indoors, safely relocate outside using a glass cup and piece of cardboard sliding underneath.
Habitat & Behavior
Habitat & Range
Widespread across Eastern North America (USA and Southern Canada). Commonly found near water sources (streams, ponds, swamps), but frequently wanders into wooded areas, basements, sheds, and homes.
Behavior & Temperament
Nocturnal ambush hunter. Generally shy, fast-moving, and skittish. When threatened, it usually flees rapidly or flattens itself against surfaces to blend into its background. Highly non-aggressive towards humans.
Diet & Prey
Generalist predator feeding on aquatic and terrestrial insects, moths, beetles, cockroaches, and occasionally small aquatic vertebrates such as tadpoles or tiny fish.
Seasonal Activity
Most frequently encountered from late spring through autumn, with mature adults being most active during mid-summer mating periods.
Description
The Dark Fishing Spider (Dolomedes tenebrosus) is one of the largest native spiders in eastern North America. Despite their intimidating size and mottled camouflage, they are beneficial, harmless wanderers that feed on household and garden pests.
Key Features
Distinct heavy banding/annulations on legs, dark W-shaped chevrons on abdomen, flattened body posture, wide dark carapace pattern with lighter margins, lack of web-weaving for prey capture.
Similar Species
Wolf Spiders (Lycosidae family, which have two much larger central eyes and distinct eye layout), Huntsman Spiders (Heteropoda venatoria, with longer, crab-like lateral leg orientation), and other Dolomedes species like D. scriptus.
Life Cycle
Females produce a large globe-shaped egg sac carried under their jaws. Before eggs hatch, the female constructs a protective nursery web in vegetation. Spiderlings disperse via ballooning or walking. Lifespan is around 1-2 years.
Ecological Importance
Acts as a vital natural pest control manager, regulating populations of insects like crickets, beetles, mosquitoes, and roaches.
Conservation Status
Not evaluated (NE) by IUCN. Population is abundant and secure throughout its native range.
Interesting Facts
Despite being called 'fishing spiders', Dolomedes tenebrosus is often found far from open water in forests and homes. They can run across the surface of water by leveraging surface tension and trapped air bubbles on their body hairs.
Photography Tips
Use a diffuse flash or soft top lighting to capture the fine surface textures, distinct leg bands, and eye layout without washing out the subtle camouflage patterns.
Identified: 2026-07-26T17:00:36.574406