Dark Fishing Spider, Dock Spider, Fishing Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae. Key family characteristics include strong, spiny legs, large sizes, and the unique habit of carrying their egg sacs in their jaws until they are ready to hatch, after which they construct a specialized nursery web.
Physical Description
Robust, large-bodied spider with a slightly flattened cephalothorax and an oval-shaped abdomen. The body is covered in fine, velvety hairs, giving it a muted matte texture. A prominent feature on this specific individual is the heavy load of hundreds of tiny spiderlings riding on her back.
Size Estimate
Body length ranges from 15 to 26 mm for females, with a massive leg span that can reach up to 70 to 90 mm (approx. 3 inches). This specimen is a large adult female, made visually even bulkier by the cluster of offspring she is carrying.
Coloration & Markings
Mottled shades of brown, gray, and tan, providing excellent camouflage against tree bark and damp ground. The cephalothorax features distinct light and dark longitudinal stripes. The legs show faint darker banding.
Web Type
These spiders do not spin webs to catch prey. Instead, they are active nocturnal hunters. Females construct temporary nursery webs of silk woven into leaves or debris only when their eggs are ready to hatch.
Eye Arrangement
Arranged in two rows of four eyes each, forming a slightly curved layout typical of nursery web spiders. The eyes are relatively equal in size compared to the dramatically enlarged anterior median eyes found in wolf spiders.
Leg Characteristics
Long, robust, and powerful legs equipped with prominent spines and scopulae (dense pads of hair) that enable them to walk across water surfaces and climb vertical structures with ease.
Venom & Safety Information
Venom Information
Contains neurotoxic components typical of large spiders, but the venom is relatively weak and non-lethal to humans. It is primarily adapted for subduing small vertebrate and invertebrate prey.
Medical Significance
Not medically significant. A bite from a fishing spider is rare and usually only occurs if the spider is directly trapped against human skin. Symptoms are typically mild, comparable to a wasp or bee sting, featuring localized pain, redness, and swelling.
Safety Recommendations
No special pest control measures are required. If found indoors or on a boat dock, simply use a container and a piece of paper to gently scoop the spider up and relocate it safely to a nearby outdoor water source or brush pile.
Habitat & Behavior
Habitat & Range
Found throughout eastern and central North America. Prefer damp habitats near streams, ponds, swamps, and lakes, but frequently venture onto wooden docks, boathouses, and occasionally the exterior walls of houses near water sources.
Behavior & Temperament
Generally non-aggressive and shy, preferring to flee or dive underwater when disturbed. However, brooding females carrying egg sacs or spiderlings may stand their ground and display a defensive posture if cornered.
Diet & Prey
Primarily carnivorous, feeding on large insects, tadpoles, small fish, and occasionally aquatic insects. They hunt by waiting at the water's edge, detecting vibrations on the water's surface, and rapidly running across the water to grab prey.
Seasonal Activity
Most active during the spring and summer months. Mating typically occurs in late spring, and brooding females with spiderlings are most commonly observed during mid to late summer.
Description
The Dark Fishing Spider is one of North America's most impressive arachnids, celebrated for its sheer size and remarkable aquatic hunting skills. Unlike web-spinning spiders, these giants patrol the margins of ponds and streams, capable of walking on water and subduing small fish. Seeing a massive female carrying hundreds of tiny spiderlings on her back, as captured here, is a breathtaking display of maternal investment in the wild.
Key Features
Large size, distinctive longitudinal stripes on the cephalothorax, sprawling leg posture, habitat near water, and the unique sight of females carrying egg sacs or masses of spiderlings.
Similar Species
Often confused with Wolf Spiders (Lycosidae). Wolf spiders carry their egg sacs attached to their spinnerets and have a distinctly different eye arrangement featuring two very large anterior median eyes. Fishing spiders carry egg sacs in their jaws.
Life Cycle
Females carry their spherical egg sacs in their chelicerae (jaws) until just before hatching, then build a tent-like nursery web. The mother guards the web until the spiderlings disperse. The spiderlings often hitch a ride on the mother's back for a short period before venturing out on their own.
Ecological Importance
Act as apex predators in micro-aquatic and riparian food webs, helping regulate insect and small amphibian populations while serving as an important food source for birds, fish, and small mammals.
Conservation Status
Not evaluated by the IUCN, but populations are generally stable and widespread throughout their native range.
Interesting Facts
Fishing spiders can remain submerged underwater for up to thirty minutes to evade predators. Despite their formidable size and appearance, they are completely harmless to humans and play a crucial role in controlling aquatic and terrestrial insect populations.
Photography Tips
Use a macro lens or a smartphone macro setting. Shoot from a slightly elevated angle to clearly capture the spider's pattern and the mass of spiderlings. Maintain a safe, calm distance to avoid startling a brooding female into fleeing.
Identified: 2026-09-18T21:48:56.467012