Indiana is home to several species of fishing spiders, large semi-aquatic arachnids found near lakes, streams, wetlands, and wooded areas throughout the state. The two most common are the dark fishing spider (Dolomedes tenebrosus) and the six-spotted fishing spider (Dolomedes triton), both of which can reach leg spans of two to four inches in females. Despite their intimidating size, these spiders are harmless to people and play an important role in riparian ecosystems.
Species Found in Indiana
The dark fishing spider is the larger and more frequently encountered of the two. Females measure 15 to 26 millimeters in body length, while males are noticeably smaller at 7 to 13 millimeters. Both sexes are brownish gray with black and lighter brown markings. Their legs display alternating brown-black banded patterns, with scalloped rings on the upper leg segments and reddish-brown rings farther down.
The six-spotted fishing spider is native throughout the contiguous United States and southern Canada, and is especially common east of the Rocky Mountains and Great Plains, putting Indiana squarely within its range. A third species, Dolomedes scriptus, also occurs in the region and can be identified by distinct white “W”-shaped markings on the back half of its abdomen.
Where They Live
Fishing spiders are typically found near bodies of water: wetland habitats, slow-moving pools, stream edges, pond margins, and lake shorelines. They’re sometimes called “dock spiders” because they’re often spotted on boat docks, where they can vanish quickly through gaps in the boards. If you spend time near any of Indiana’s reservoirs, creeks, or farm ponds, you’ve likely been within a few feet of one.
They also venture into nearby woods for terrestrial hunting, which is why the dark fishing spider frequently turns up on tree trunks, rock faces, and the sides of cabins or outbuildings well away from water. This woodland wandering is what brings them into contact with people most often.
How They Hunt on Water
Fishing spiders are one of the few spider groups that can walk on water, and they do it by spreading their long legs across the surface film to distribute their weight. Their flattened body shape helps them sit low on the water without breaking through. When they detect ripples from a small fish, tadpole, or aquatic insect, they can dash across the surface to grab it.
They rely almost entirely on touch and vibration to detect prey, using vision only as a secondary sense. They’re also capable of fully submerging, diving beneath the surface to catch aquatic invertebrates or to escape threats. Researchers have noted that semi-aquatic spiders need to reach a certain body size before they can intentionally break through surface tension to forage underwater, which helps explain why fishing spiders are so much larger than most other species you’ll encounter.
This predatory behavior makes them ecologically valuable. Fishing spiders are important to nutrient cycling in riparian systems, moving energy between aquatic and terrestrial food webs by consuming prey from both.
Fishing Spider vs. Wolf Spider
These two get confused constantly because they overlap in size, color, and habitat. Both are large, brown, fast-moving spiders that don’t build webs. But a few reliable differences make identification straightforward once you know what to look for.
- Eyes: Wolf spiders have two oversized “headlight” eyes in the middle row that reflect brightly when you shine a flashlight at night. Fishing spiders have eight eyes that are all roughly the same size, arranged in two slightly curved rows, with no dramatic reflective glow.
- Body shape: Fishing spiders have flat bodies and legs that spread wide and low, an adaptation for sitting on water. Wolf spiders are more compact and muscular, with rounder, arched bodies built for running on land.
- Proportions: Fishing spiders have noticeably longer legs relative to their body, giving them a stretched-out appearance. Wolf spiders look heavier and stockier by comparison.
- Leg span: Female fishing spiders can reach leg spans of two to four inches. Wolf spiders top out around one to three inches.
The flashlight test is the easiest field method. Walk around your yard or dock at night with a headlamp. If you see bright green eyeshine from the ground, that’s a wolf spider. Fishing spiders won’t produce the same effect.
Why They Show Up Indoors
Fishing spiders, particularly the dark fishing spider, occasionally wander into homes, garages, and basements in Indiana. This happens most often in late summer and early fall, when males are roaming in search of mates and when cooler nighttime temperatures drive insects (and the spiders that follow them) toward structures. Homes near wooded areas or water are the most likely to get visitors.
These spiders aren’t trying to establish themselves inside your house. They’re accidental intruders that would rather be outside. But their size makes them startling when they appear on a basement wall or in a bathtub.
Keeping Them Out of Your Home
The most effective approach is physical exclusion. Install tight-fitting window screens and door sweeps to close off entry points. Trim back shrubs, vines, and tree limbs that touch the house, since these give spiders a direct bridge to exterior walls. Move firewood, stacked materials, and debris away from the foundation, as these create sheltered habitat right next to potential entry points.
Inside, reducing clutter in basements, garages, closets, and attics makes those spaces less appealing. Routine, thorough cleaning is the single best way to discourage spiders from settling in. Vacuuming corners, behind furniture, and along baseboards removes both spiders and the insects they feed on.
Switching outdoor lights near entrances to yellow or sodium vapor bulbs helps too. Standard white bulbs attract night-flying insects, which in turn draw spiders to your doorstep. Yellow bulbs are far less attractive to insects, reducing the food supply that keeps spiders hanging around. If you want a chemical option, perimeter barrier sprays applied around the foundation can reduce spider entry, though they typically need reapplication every month or two during warmer weather. Wear heavy gloves when moving boxes, firewood, or other stored materials where a spider might be resting.
Are They Dangerous?
Fishing spiders can bite if handled roughly or trapped against skin, but their venom is not medically significant to humans. A bite is comparable to a bee sting: brief pain, minor swelling, and that’s typically the end of it. They are not aggressive and will flee from people when given any opportunity. The spiders you should actually watch for in Indiana are brown recluses and black widows, both of which are far smaller and less conspicuous than a fishing spider.