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 the abdomen is elongated-oval, covered in fine hairs giving it a velvety texture. They have distinct lateral posture adjustments when resting on vertical surfaces.
Size Estimate
Body length ranges from 15 to 26 mm for females, with a massive leg span reaching up to 70 to 90 mm. This specimen appears to be a subadult or adult female.
Coloration & Markings
Mottled pattern of grayish-brown, dark brown, and black, interspersed with lighter patches and distinct dark, W-shaped chevrons along the dorsal abdomen. Legs are strongly banded with alternating light and dark rings.
Web Type
None. These are wandering hunters that do not spin webs to catch prey, though females construct silken nursery webs for their egg sacs.
Eye Arrangement
Eight eyes arranged in two rows of four, typical of Pisauridae, with eyes being relatively equal in size compared to the distinct anterior median enlargement in Lycosidae.
Leg Characteristics
Long, powerful legs featuring prominent spines and distinct dark banding. They are typically held sprawling outward against a surface to maximize tactile detection of vibrations.
Venom & Safety Information
Venom Information
Contains neurotoxic components typical of large wandering spiders, but the venom is generally weak regarding human physiology and primarily specialized for subduing vertebrate and invertebrate prey.
Medical Significance
Not medically significant. Bites are rare, typically only occurring if trapped against the skin. Symptoms are usually mild, comparable to a bee sting, involving localized pain and swelling.
Safety Recommendations
Keep calm if encountered indoors. To relocate, place a clear container over the spider, slide a stiff piece of card underneath, and release it outdoors near a wooded or damp area. No pest control is necessary.
Habitat & Behavior
Habitat & Range
Found across eastern North America. Prefers wooded areas near bodies of water such as streams, ponds, and lakes, but frequently wanders onto vertical walls of buildings, tree trunks, and docks.
Behavior & Temperament
Nocturnal and crepuscular active hunter. Highly agile and fast-moving. Timid toward humans, preferring to flee or hide, but females guarding egg sacs can display defensive postures.
Diet & Prey
Primarily feeds on large insects, aquatic insects, small fish, tadpoles, and occasionally small amphibians by detecting surface water vibrations or ambushing on land.
Seasonal Activity
Most active from late spring through autumn. Overwinters as juveniles or subadults beneath loose bark, under logs, or occasionally inside outbuildings.
Description
The Dark Fishing Spider is one of North America's largest and most impressive wandering spiders. Often startling homeowners when found on the sides of houses far from water, this velvety giant is an expert camouflage artist, blending seamlessly into tree bark and weathered wood. Despite its intimidating size and hunting prowess on both land and water surface film, it poses virtually no threat to humans and plays an important role in controlling aquatic and terrestrial insect populations.
Key Features
Large size, sprawling leg posture, mottled grey-brown coloration with W-shaped abdominal chevrons, heavily banded legs, and habitat often associated with vertical wooden or stone surfaces near water.
Similar Species
Wolf spiders (Lycosidae) and other Dolomedes species such as Dolomedes scriptus. Distinguished from wolf spiders by not carrying egg sacs attached to spinnerets and possessing a different eye arrangement.
Life Cycle
Females carry their round egg sacs in their jaws until just before hatching, then construct a silken nursery web in vegetation where spiderlings molt before dispersing.
Ecological Importance
Acts as an apex invertebrate predator linking aquatic and terrestrial food webs, providing natural biocontrol for mosquitoes, aquatic insects, and various garden pests.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and common throughout their native North American range.
Interesting Facts
Despite being called fishing spiders, they are capable of walking on water and can even dive beneath the surface for short periods to escape predators or hunt small fish and tadpoles.
Photography Tips
Photograph from a safe distance using a macro or telephoto lens. Capture dorsal shots to clearly show the abdominal chevrons and lateral leg banding under natural diffused lighting.
Identified: 2026-10-09T15:07:59.840035