Dark Fishing Spider, Vol. 8, No. 25
Dolomedes tenebrosus
Order: Araneae
Family: Pisauridae
“We had this big, gray spider sitting on the brick wall, just under the eaves of our house. This was the biggest spider I’ve ever seen! Its legs spanned across one brick and both mortar joints. What kind of spider is this and are they dangerous?”
Dark fishing spiders are some of the largest spiders in the state. A large female can be an inch long with a 3+-inch leg span. As the photo shows, they are also well camouflaged, with markings and hairy bodies that allow them to blend with tree bark. The camouflage helps protect them from birds and other predators while they rest during the day, usually on the trunk of a tree with their head facing down. These spiders hunt mostly at night. Color varies from grey to dark brown, but this is also true for tree bark.
Despite their name, dark fishing spiders are more often found in wooded areas that may be well away from water, where they prey on a variety of large insects and other prey. They do not build webs but catch their meals by stalking or ambushing them. Dark fishing spiders sometimes occur around building exteriors, such as decks and patios, and occasionally they make their way indoors, where they usually cause “significant consternation” because of their size.
Their bite is not seriously venomous, but it is painful; folks who have been bitten compare it to the pain of a bee or wasp sting. Bites are rare; it is difficult to find someone who has been bitten by a fishing spider. This is not true for male fishing spiders, which are often cannibalized by females after mating, sometimes even before mating. In fact, this tendency to eat their partners and potential partners seems to be more common in fishing spiders than in black widow spiders, though males of both species also sometimes survive mating encounters.
Why are they called fishing spiders if they don’t live around water? When they live around water, dark fishing spiders do catch small fish, but this name is more applicable to other members of the genus. Striped fishing spiders, Dolomedes scriptus, are the same size and look very similar to dark fishing spiders but are more often found in aquatic habitats, where adult spiders prey on minnows and other small vertebrates, such as frogs, tadpoles, and young lizards. Dolomedes okefinokensis, which occurs where you might think it does, has even been observed eating small snakes. Fishing spiders also prey on insects, and other aquatic invertebrates, including crawfish. Despite their notoriety for feeding on vertebrates, insects comprise the largest part of their diet because young spiders can only handle small prey.
Six-spotted fishing spiders, Dolomedes triton, are the real fishermen of the group. Though a bit smaller than the other species, adults are more specialized in preying on tiny minnows and tadpoles. These amazing spiders can walk on water, dive under water, breathe under water and hunt under water. This is also true of the other species, but six-spotted fishing spiders hunt by day and are easier to observe. They also feed on insects and other invertebrates, especially when young.
See Bug’s Eye View No. 7 of 2021, for a brief article on Trapdoor spiders , which are the largest, and one of the most unusual, spiders in the state.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service. The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled. Mississippi State University is an equal opportunity institution.
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