Pennsylvania homes host about a dozen common spider species, and nearly all of them are harmless. The spiders you’re most likely to find indoors are the common house spider, the longbodied cellar spider, wolf spiders, and various sac spiders. Only two species in the state carry medically significant venom, and one of them, the brown recluse, is extremely rare in Pennsylvania.
Common House Spider
The spider most Pennsylvanians encounter indoors is, fittingly, the common house spider. Females are 5 to 6 millimeters long (roughly the size of a pencil eraser) with a yellowish-brown head and a dirty-white to brown body marked with gray chevrons. Some have a triangular black spot on top of the abdomen. Males are slightly smaller, around 4 millimeters, with orange legs. Both sexes have yellow legs banded with darker rings at each joint.
These spiders build messy cobwebs in wall corners, window frames, and floor joists. They have a habit of abandoning webs and spinning new ones nearby, which is why a single spider can make a room look neglected fast. They strongly prefer damp areas, so basements and crawl spaces are their favorite spots. Despite their abundance, their bites are not considered medically dangerous.
Cellar Spiders
The longbodied cellar spider is another fixture of Pennsylvania basements, garages, and crawl spaces. These are the pale, impossibly leggy spiders you see hanging upside-down in loose, irregular webs. Females are 7 to 8 millimeters in body length, but their front legs stretch to about 50 millimeters, giving them a spindly appearance that’s easy to recognize. Their bodies are pale tan or yellow with a gray mark in the center of the head.
Cellar spiders thrive in dark, quiet, protected spots and can build large populations in undisturbed areas. They’re active in heated buildings year-round. Despite their creepy appearance, they do not bite people and pose zero health risk. If anything, they’re beneficial: they catch and eat other insects and even other spiders that wander into their webs.
Wolf Spiders
Wolf spiders are the ones that startle people. They’re large, fast, and they don’t build webs. Instead, they hunt at night. Pennsylvania is home to several species, with the two most common being noticeably big. The Carolina wolf spider is the larger of the two: females reach 22 to 35 millimeters (well over an inch), dark brown with scattered gray hairs and a darker stripe down the back. The tiger wolf spider is slightly smaller at 18 to 25 millimeters, similar in color but with a distinct narrow line of yellow hairs near the eyes and lighter banding at the leg joints.
During warmer months, wolf spiders live outdoors in retreats they dig under stones, boards, firewood, and siding. They enter homes most often in autumn. Fertilized females seek protected spots to overwinter, and human-made structures fit the bill perfectly. Males mate in fall and die before winter, so the large wolf spiders you find inside during cold months are almost always females. They produce egg sacs the following May or June, and the young spiders take over a year to reach full size.
Wolf spiders can bite if handled or trapped against skin, but their venom isn’t dangerous to people. The bite feels similar to a bee sting.
Other Spiders You Might See Indoors
Several other species regularly turn up in Pennsylvania homes:
- Jumping spiders are small, compact, and surprisingly cute. Pennsylvania has several species, including the bold jumper, zebra jumper, bronze jumper, and emerald jumper. They have large forward-facing eyes and move in short, quick hops. They’re active during the day, hunt without webs, and are completely harmless.
- Barn funnel weavers build flat, sheet-like webs with a funnel-shaped retreat in one corner. You’ll see these in garages, sheds, and basement windows. They’re brown and medium-sized, and they dart back into their funnel when disturbed.
- Sac spiders (agrarian and longlegged varieties) are pale yellow or tan and build small silk tubes in upper wall corners or where the ceiling meets the wall. They hunt at night and are one of the more common spiders responsible for minor bites indoors, though the bites are not serious.
- Parson spiders are dark, ground-dwelling hunters with a distinctive white stripe on the abdomen. They’re fast runners and sometimes show up in bedding or clothing left on the floor.
- Woodlouse hunters have an unusual look: a reddish-orange head, cream-colored abdomen, and oversized fangs designed for eating pill bugs. They sometimes wander indoors but are not aggressive toward people.
Are Any Pennsylvania House Spiders Dangerous?
Pennsylvania has two spider species with medically significant venom: the southern black widow and the brown recluse. In practice, neither one is a common house spider in the state.
The southern black widow lives in Pennsylvania but prefers undisturbed outdoor locations like woodpiles, stone walls, and outbuildings. Finding one inside a living space is uncommon. Brown recluse spiders are even rarer. Pennsylvania falls outside their established range, which covers sixteen states concentrated in the South and Midwest. The only brown recluses found in Pennsylvania were transported in from elsewhere, typically in moving boxes. They don’t survive outdoors in the state and remain isolated to the specific building where they were introduced. Penn State Extension describes the risk of being bitten as “virtually nonexistent.”
For the vast majority of Pennsylvania house spiders, a bite produces a reaction similar to a bee sting: redness, pain, and swelling at the site. Occasionally someone will experience a headache or mild nausea. Clean the bite with soap and water, apply antibiotic ointment, and use over-the-counter hydrocortisone cream or antihistamines if swelling is significant. If you can, save the spider (even dead) for identification.
Keeping Spiders Out of Your Home
Spiders follow their food. If insects are getting into your house, spiders will too. The most effective long-term strategy is making your home less inviting to both.
Start with sealing entry points. Caulk cracks around windows, doors, foundation walls, and where pipes or wiring enter the house. Pay attention to gaps under siding and around basement windows, since wolf spiders and funnel weavers use these as highways. Inside, vacuum regularly in high and low spots, including behind furniture, along baseboards, and in ceiling corners. Removing webs consistently discourages spiders from rebuilding in the same area.
Reduce sheltering sites by clearing clutter in basements, garages, and attics. Cardboard boxes are especially attractive to spiders. If you’re storing items long-term, switch to sealed plastic bins. When rummaging through storage areas, attics, or woodpiles, wear gloves.
Outdoor lighting draws insects to your home’s exterior, which in turn draws spiders. Switching to yellow or sodium vapor bulbs, or simply turning off unnecessary exterior lights, reduces the insect buffet near your doors and windows. Some people apply insecticide around their foundation in autumn to intercept outdoor spiders migrating indoors, and sticky traps placed along walls in basements and garages can catch wandering hunters like wolf spiders and parson spiders without chemicals.