Dark Fishing Spider, Dock Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae
Physical Description
Large, robust body with a somewhat flattened appearance. The cephalothorax is broad and rounded, while the abdomen is elongated oval-shaped. Covered in fine velvety hair with a somewhat rugged texture, typical of large hunting spiders.
Size Estimate
Body length ranges from 15 to 26 mm for females and slightly smaller for males, with a formidable leg span reaching up to 70 to 90 mm. This specimen appears to be a mature or nearly mature adult.
Coloration & Markings
Predominantly dark brown to charcoal grey, featuring distinct dark, W-shaped or chevron-like bands across the legs and alternating dark and light markings along the sides of the carapace and abdomen.
Web Type
Does not build a web to capture prey. Uses silk only for safety lines, wrapping egg sacs, and constructing temporary nursery webs for their young.
Eye Arrangement
Eight eyes arranged in two distinct rows of four, set in a compact, slightly curved configuration typical of the Pisauridae family, with the anterior median eyes often smaller.
Leg Characteristics
Long, powerful legs with prominent dark banding and robust spination. They are held sprawled out flat against surfaces to help distribute weight, enabling the spider to run across water surfaces.
Venom & Safety Information
Venom Information
Neurotoxic and proteolytic venom designed to immobilize small vertebrate and invertebrate prey. Potency to humans is very low and generally poses no serious health risk.
Medical Significance
Not medically significant. A bite may cause localized pain, swelling, and redness similar to a bee sting, but they rarely bite humans unless firmly pressed against the skin.
Safety Recommendations
Avoid handling them bare-handed near water docks or woodpiles. If found indoors, gently guide them into a container using a piece of cardstock and release them safely outdoors near a water source.
Habitat & Behavior
Habitat & Range
Found across eastern North America, typically inhabiting wooded areas near streams, ponds, lakes, and swamps, often resting on tree trunks, rocks, or docks near water.
Behavior & Temperament
Active nocturnal hunter that actively stalks or ambushes prey. They are generally timid and prefer to flee or run across the water when disturbed, though females guarding nurseries may show defensive postures.
Diet & Prey
Consists primarily of aquatic insects, small fish, tadpoles, and terrestrial invertebrates caught near the water's edge using rapid bursts of speed and strong chelicerae.
Seasonal Activity
Most active from late spring through early autumn, with mating occurring in the summer months. They overwinter as juveniles or sub-adults under loose tree bark or in sheltered crevices.
Description
The Dark Fishing Spider is a magnificent, robust arachnid often found near bodies of water in eastern North America. Despite its intimidating size and resemblance to a wolf spider, it is a shy creature that prefers to bolt across water or hide beneath loose bark rather than confront humans. Their remarkable hunting abilities allow them to capture not only large insects but occasionally small aquatic vertebrates.
Key Features
Large size, dark brownish-grey coloration with prominent chevron banding on the legs, distinct facial eye arrangement, and an association with aquatic or heavily wooded shoreline habitats.
Similar Species
Wolf spiders (Family Lycosidae) and nursery web spiders like Pisaurina mira. Wolf spiders carry egg sacs attached to their spinnerets instead of holding them in their jaws, and fishing spiders often rest with their front legs paired together.
Life Cycle
Females carry their round egg sacs in their jaws until they are ready to hatch, at which point they construct a silken nursery web in vegetation and guard it until the spiderlings disperse after their first molts.
Ecological Importance
Acts as an important apex predator in riparian and wetland microhabitats, helping to control insect populations and serving as a food source for larger birds, amphibians, and mammals.
Conservation Status
Not evaluated by the IUCN, but populations are generally stable and widespread throughout their natural eastern North American range.
Interesting Facts
Dark fishing spiders possess the rare ability to walk and run rapidly across the surface tension of water. Some larger individuals have been observed successfully subduing small fish and tadpoles by dragging them to the shore.
Photography Tips
Photograph from a low angle to capture their natural posture and leg span. Use a macro lens in natural or diffused lighting, maintaining a respectful distance to avoid startling them into rapid flight.
Identified: 2026-09-06T20:20:31.212605