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Dark Fishing Spider (Dolomedes tenebrosus)

Dolomedes tenebrosus

The Dolomedes tenebrosus, the massive 'Dark Fishing Spider'. It is one of the most imposing spiders in the United States (reaches 3.9 inches legspan). Unlike its strictly aquatic cousins (D. triton), the tenebrosus is an arboreal and terrestrial hunter that inhabits damp woods, although it can walk and dive in the water if necessary. It is a very fast wandering spider, with a flattened and camouflaged body (gray, brown, mottled), morphologically similar to a giant wolf spider. Devoid of webs to hunt, it physically pursues prey. Absolutely harmless and fearful, it is a fantastic display for those who love large active spiders that do not require complicated water tanks.

Taxonomy
Class:Arachnida
Order:Araneae
Family:Dolomedidae
Genus:Dolomedes
Species:Dolomedes tenebrosus

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Environment

Terrestrial

Humidity

60 - 80 %

Day temperature

21 - 26 °C

Night temperature

18 - 21 °C

UVB

None

Species description

Geographic Origin and Habitat: University of Minnesota Extension reports Dolomedes tenebrosus associated with ponds, swamps, and slow-moving streams; it also reports occurrence at a distance from water sources. The page records activity in spring and summer.
Taxonomy and Genetics: The cited University Extension page identifies the fishing spider as Dolomedes tenebrosus. It provides no genetic result, synonymy, or additional taxonomic treatment; none is inferred here.
Behaviour and Habits: The source describes predation on insects and occasionally small vertebrates, including tadpoles and small fish. This describes natural history, not a captive feeding recommendation.
Morphology and Sexual Dimorphism: The page describes a length of 1 1/4 inches and up to 3 1/2 inches including the legs. It reports varying shades of brown, usually three chevron markings on the abdomen, and banded legs. It supplies no sex-specific comparison.

Care, breeding and tankmates

Terrarium Setup: University of Minnesota Extension reports that Dolomedes tenebrosus is associated with ponds, swamps, and slow-moving streams, but can also occur at a distance from water sources. This natural-history record does not specify enclosure dimensions, substrate, furnishings, or a captive setup protocol.
Lighting and Heating: The cited source reports activity in spring and summer but gives no captive photoperiod or temperature target; none is inferred here.
Humidity and Hydration: The cited source describes associations with water and records away-from-water occurrence, but gives no captive humidity target or hydration protocol; none is inferred here.
Feeding and Supplementation: The source describes predation on insects and occasionally small vertebrates, including tadpoles and small fish. This natural-history observation does not establish captive prey size, frequency, portions, or supplementation.
Compatibility and Coexistence: The cited source provides no cohabitation or handling guidance; none is inferred here.
Health and Common Diseases: The page states that, despite its size, the species does not harm people. It provides no disease, treatment, or veterinary-management guidance.

Geographic Origin and Distribution

This species originates from: Nord America (Foreste umide, corsi d'acqua e tronchi in decomposizione del Nord America orientale).

Origin

Selective breeding and cultivarsNorth America

Terrestrial invertebrate profile

Diet
No verified data available
Life expectancy
No verified data available
Adult size
3.18 cm
The catalog's scalar value is 3.18 cm. The University of Minnesota Extension — Dark Fishing Spider source reports a maximum adult measurement of 3.18 cm for this species, recorded as body length. The taxonomic record consulted is Dolomedes tenebrosus. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
Lifestyle/Microhabitat
No verified data available
Activity cycle
No verified data available
Sociality
No verified data available
Reproduction
No verified data available
Venom level
No verified data available
Handling tolerance
No verified data available
Brumation
No verified data available
Molting
No verified data available

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

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Last updated: 08/10/2026
Dark Fishing Spider (Dolomedes tenebrosus) Care Guide & Terrarium Setup | Atlarium