Fishing Spiders: Size, Bites and Why They Turn Up Indoors
Fishing spiders (genus Dolomedes) are large, shy, web-less hunting spiders that are harmless to people: they rarely bite, and a bite is usually compared to a bee or wasp sting. The one most often found in houses, the dark fishing spider, has a female body 15 to 26 mm long (about 0.6 to 1 inch) with legs spanning 3 inches or more. Despite the name, it lives mainly on trees in woodland, often well away from water, and wanders into basements, sheds and decks from spring to autumn.
A fishing spider is usually the biggest spider anyone in the eastern half of the US will ever see on a wall, which is why it causes so much alarm. The answers to the usual questions are reassuring, and the biology is stranger than most people expect: these spiders gallop across ponds, leap straight up off the water to dodge frogs, and the males die during their first mating.
Fishing spider or wolf spider?
Fishing spiders and wolf spiders are both large, brown, hairy hunters that run rather than sit in a web, and Penn State Extension notes the two are similar in size, shape and colouration. A few features separate them reliably.
| Feature | Fishing spider (Dolomedes) | Wolf spider (Lycosidae) |
|---|---|---|
| Front row of eyes | Four eyes, the outer two set higher than the inner two | Four small eyes in a straight line, facing forward, below two very large eyes |
| Egg sac | Carried in the jaws, under the body | Attached to the spinnerets at the rear |
| Young | Guarded in a “nursery” of silk and folded leaves | Ride on the mother’s back |
| Where it rests | Vertical surfaces: tree trunks, walls, decks, often head down | On the ground, in leaf litter, mulch or a burrow |
| Legs | Very long, banded, held splayed flat | Stout, often banded, visibly spined |
| Typical body length | Dark fishing spider female 15 to 26 mm | Carolina wolf spider female 22 to 35 mm |
| Bite | Rare; compared to a bee or wasp sting | Rare; symptoms usually gone within 24 hours |
NC State Extension gives the eye test: with a hand lens, the front four eyes of a fishing spider curve so that the outer two sit higher than the inner two, while a wolf spider’s front four form a straight line. In practice, posture tells you faster. A spider sitting spread-eagled on a vertical wall or a tree trunk with its legs splayed flat is almost always a fishing spider; a spider running across the floor is more often a wolf spider. Our full wolf spider guide covers the eyeshine test and the mother carrying her young.
How big do fishing spiders get?
Females are far larger than males. Penn State gives dark fishing spider females 15 to 26 mm in body length and males 7 to 13 mm. The legs are what make them look enormous: Mississippi State Extension says a large female can be an inch long with a leg span of more than 3 inches, and the University of Minnesota puts the length including legs at up to 3.5 inches (about 89 mm). The Missouri Department of Conservation gives the spotted, or six-spotted, fishing spider a body length of about three quarters of an inch for females and half an inch for males.
The University of Maine calls the genus Maine’s largest native spider. Size is not a guide to danger, and a large size helps rule out the small, medically significant spiders covered in our spider identification guide.
The species you are likely to meet
| Species | Where it lives | Identification notes |
|---|---|---|
| Dark fishing spider, Dolomedes tenebrosus | Wooded areas, often far from water; the common house invader. New England and Canada south to Florida and Texas | Brownish grey with black and lighter brown markings, chevrons on the abdomen, banded legs |
| Striped fishing spider, D. scriptus | More closely tied to streams and wetlands | Similar to the dark fishing spider but with white “W” marks on the rear of the abdomen |
| Six-spotted or spotted fishing spider, D. triton | Ponds, slow streams, swamps and other damp places | Dark, with a pale stripe around the carapace and pairs of small white spots down the abdomen; hunts by day |
Are fishing spiders dangerous?
No, not to healthy people. Penn State calls them harmless and says they rarely bite even when grabbed, and that a bite is typically no more severe than a bee or wasp sting, with exceptions in people who are sensitive to spider venoms. Mississippi State says the bite is painful but not seriously venomous, and that it is difficult to find someone who has been bitten. NC State states that their venom is not dangerously toxic to humans. The University of Maine adds that they are very shy and would rather flee than fight.
Are fishing spiders aggressive?
No. Penn State describes them as quite shy, generally running from people at the slightest movement. Bites happen when a spider is grabbed or pressed against skin. Anyone with an unusual reaction to any bite or sting should speak to a doctor, and our bite identification guide explains why most “spider bites” turn out to be something else.
Are fishing spiders poisonous, and can one kill you?
Strictly, spiders are venomous rather than poisonous, since they inject venom by biting. A fishing spider has venom for subduing insects, tadpoles and small fish, but no extension source we read records a serious injury, let alone a death, from one. CDC names only two venomous spider groups of concern in the United States, the black widow and the brown recluse, and says that even with those, death is extremely rare.
Can a fishing spider hurt a cat or dog?
We found no extension or veterinary source documenting harm to a pet from a fishing spider. A pet that has been bitten by anything and shows swelling, distress or lethargy should be seen by a vet.
Do fishing spiders make webs?
Not to catch prey. Mississippi State says they do not build webs but catch their meals by stalking or ambushing them. The only web involved is the nursery: NC State describes the female tying leaves together and suspending her egg sac in that silk nursery when hatching approaches, then guarding the eggs and young, which leave after about a week. Penn State says a single nursery may hold 1,000 or more young. If you have found a big spider and a tangle of leaves and silk on a shrub in midsummer, that is the nursery, and NC State notes it is the only “damage” these spiders do to plants.
How fishing spiders hunt on water
A fishing spider rests its front legs on the water and feels for vibrations, rushing out when an insect falls in, as the Missouri Department of Conservation describes. Its body is strongly water-repellent, and it moves using two main gaits. Rowing sweeps the legs backwards against small dimples they make in the surface, which push back like an oar against water. Galloping, described by Robert Suter of Vassar College in a 2013 review in the Journal of Arachnology, uses downward and backward thrusts of the first three pairs of legs to produce a string of leaps off the water.
Size barely matters on water. Suter and Gruenwald found that newly emerged six-spotted fishing spiders row at about the same speed as adults despite a roughly 600-fold difference in mass (1.7 mg against 1.1 g), which works out at about 42 body lengths a second for the smallest spiders against about 6 for the largest. Fishing spiders also sail: a spider that raises its body and legs catches the wind and drifts across a pond for almost no energy, at the cost of losing control of its direction.
Do fishing spiders jump?
Yes, though not like jumping spiders. On water they can leap straight upwards by pressing all eight legs down at once, so the sideways forces cancel and the spider rises with little forward movement. Suter’s review reports that these vertical jumps are quite effective at evading frogs attacking from the side, and that the trigger is the pressure wave pushed ahead of the frog, detected by sensory hairs on the legs. They can also dive: Missouri notes that a fishing spider can submerge inside a coat of air, often for several minutes.
Do they really catch fish?
Sometimes. Nyffeler and Pusey reviewed more than 80 records of semi-aquatic spiders catching fish worldwide (PLoS ONE, 2014). Fishing spiders of the genera Dolomedes and Nilus accounted for more than 75 per cent of the records, the fish were usually 2 to 6 cm long, and on average they were 2.2 times the spider’s own body length. In the southeastern US the usual catch was mosquitofish. The authors treat fish as an occasional prey item; Mississippi State notes that insects make up the largest part of the diet, because young spiders can only handle small prey.
Males die after mating
The dark fishing spider has one of the strangest mating systems known in spiders. Schwartz, Wagner and Hebets at the University of Nebraska reported in Biology Letters (2013) that males mate with a single female, and that mating results in obligate male death and genital mutilation. Males fill both of their sperm-delivery organs but use only one before collapsing. Males could tell virgin from mated females by the silk they leave behind. Females usually eat the dead male, which may benefit his offspring.
Why would a fishing spider be in my house?
Because the house is the edge of its habitat. Penn State calls the dark fishing spider a tree-dwelling spider and a common household invader in wooded locations, and notes that it overwinters as a nearly mature spider under stones or loose bark, in tree cavities and in human-made structures, maturing in spring. Mississippi State says they turn up around decks and patios and occasionally make their way indoors. So houses near woods, creeks or lakes see them, in basements, garages and sheds, all covered in our guide to bugs in the basement.
They are not breeding indoors: a fishing spider in the house is a single wanderer that came in through a gap.
When they turn up
Penn State says mature dark fishing spiders are found from early May through September, egg sacs are made in June and spiderlings appear from July through September. Our analysis of iNaturalist research-grade records matches that: dark fishing spider sightings in the US are at their highest share of all records in June (an index of 176, where 100 is the yearly average) and fall to 25 in January. Wolf spiders, by contrast, peak in October, which is why a big brown spider in an autumn living room is more often a wolf spider and one on a deck in early summer is more often a fishing spider.
Where fishing spiders are recorded most
Fishing spiders occur across most of the US, but they are recorded most often, relative to everything else people photograph, in the wooded, well-watered states of the Appalachians and the Southeast. West Virginia (22.35 records per 10,000 iNaturalist observations), Kentucky (22.13) and Tennessee (20.4) lead, followed by North Carolina, Virginia and Ohio. Minnesota is the northern outlier in the top 14. These are records of where people photographed and identified the spiders, mostly outdoors, not counts of spiders in houses.
What to do about a fishing spider
| Situation | What usually works |
|---|---|
| One spider on an indoor wall | A large jar or tub and a sheet of card; release it outside near trees or water |
| Spiders on a deck, dock or boathouse | Leave them; they eat insects, including aquatic insects. Move outdoor lights away from doors to reduce the insects that draw them |
| Repeated sightings in a basement | Seal gaps at sill plates, window wells, doors and utility lines; reduce clutter and dampness |
| A nursery web on a shrub | Leave it; the young disperse within about a week |
| Strong fear of spiders | NC State accepts swatting or a household aerosol on the single spider; follow the label, and do not fog |
NC State says plainly that these are not household pests. There is no indoor population to treat, so spraying rooms or setting off foggers only exposes the household to a product. Repeated sightings point to gaps in the building, and our guide to getting rid of spiders in the house sets out the sealing and decluttering steps. Worried about one on the bedroom wall? Our article on whether spiders bite in your sleep explains why bites in bed are so rare.
Frequently asked questions
Are fishing spiders harmful?
Not to healthy people. Penn State Extension calls fishing spiders harmless and says they rarely bite even when grabbed. When a bite does happen it is usually compared to a bee or wasp sting, with stronger reactions possible in people sensitive to spider venom. They are shy and run from movement. Anyone with a worrying reaction to any bite should see a doctor.
What is the #1 deadliest spider?
No spider kills many people today. The Sydney funnel-web of Australia has a venom that can, in the worst cases, be fatal, but the Australian Museum reports no deaths since its antivenom was introduced. In the United States, CDC names the black widow and brown recluse as the venomous spiders of concern and says death is extremely rare. Fishing spiders are not on either list.
How large do fishing spiders get?
Female dark fishing spiders have a body 15 to 26 mm long, about 0.6 to 1 inch, and males 7 to 13 mm, according to Penn State. With legs spread, Mississippi State says a large female spans more than 3 inches, and the University of Minnesota gives up to 3.5 inches including legs, which makes them among the largest spiders in eastern North America.
Why would a fishing spider be in my house?
Dark fishing spiders live mainly on trees in woodland and overwinter under bark, stones and in buildings, so homes near woods, creeks or lakes get occasional wanderers, especially into basements, garages and sheds. They come in through gaps around doors, windows and utility lines. They do not breed indoors, so one spider is just one spider; release it outside and seal the entry.
Sources
- Penn State Extension, Fishing Spider (Dolomedes tenebrosus), Steve Jacobs; and Wolf Spiders.
- NC State Extension, Fishing Spiders and Wolf Spiders.
- Mississippi State University Extension, Bug’s Eye View: Dark Fishing Spider, Vol. 8, No. 25, Blake Layton, 2022.
- University of Minnesota Extension, What insect is this? Dark fishing spider.
- University of Maine Cooperative Extension, Home and Garden IPM: Fishing Spiders.
- Missouri Department of Conservation, Field Guide: Spotted Fishing Spider.
- Suter, R. B., Spider locomotion on the water surface: biomechanics and diversity, Journal of Arachnology 41:93 to 101, 2013.
- Suter, R. B. and Gruenwald, J., Spider size and locomotion on the water surface, Journal of Arachnology 28:300 to 308, 2000.
- Suter, R. B., Cheap transport for fishing spiders: the physics of sailing on the water surface, Journal of Arachnology 27:489 to 496, 1999.
- Nyffeler, M. and Pusey, B. J., Fish predation by semi-aquatic spiders: a global pattern, PLoS ONE 9(6): e99459, 2014.
- Schwartz, S. K., Wagner, W. E. and Hebets, E. A., Spontaneous male death and monogyny in the dark fishing spider, Biology Letters, 2013.
- CDC NIOSH, Venomous Spiders.
- Australian Museum, Sydney Funnel-web Spider, 2025.
- The Pest Control Brief analysis of iNaturalist research-grade records, pulled October 2026.
