Most homes harbor a handful of spider species, and the vast majority are harmless. The spiders you’re likely to find indoors fall into a few recognizable groups: cobweb builders tucked into corners, long-legged cellar spiders hanging in basements, active hunters like jumping spiders and wolf spiders, and the occasional yellow sac spider roaming walls at night. Knowing which is which can save you unnecessary worry and help you decide which ones to leave alone.
Common House Spiders
The spider most often called “the common house spider” (Parasteatoda tepidariorum) is the one responsible for those messy, tangled cobwebs in window frames, garage corners, and behind furniture. These are small, brownish spiders with rounded abdomens and a mottled pattern. They’re completely harmless and rarely move far from their webs. If a web stops catching prey, they’ll abandon it and spin a new one nearby, which is why cobwebs accumulate in undisturbed parts of your home.
Cellar Spiders
Cellar spiders are the fragile, wispy spiders with extremely long, thin legs that hang upside down in basements, closets, and dim corners. Their bodies are usually no more than a quarter inch long, but their leg span makes them look much larger. They’re typically gray, tan, or whitish, and some species have darkened joints that give them a knobby-kneed appearance. Most have peanut-shaped abdomens.
When disturbed, cellar spiders vibrate rapidly in their webs, bouncing so fast they become a blur. This is a defensive behavior meant to confuse predators. Their webs are messy and non-sticky. Instead of using adhesive silk, they rely on a dense, tangled matrix of threads to snare prey, then throw long strands of silk to wrap their catch from a safe distance.
Cellar spiders punch well above their weight. They routinely capture prey much larger than themselves, including wolf spiders and crane flies. Some species even invade other spiders’ webs, jiggle the silk to mimic a trapped insect, and then eat the host spider when it comes to investigate. Because they devour so many other spiders and insects, many people deliberately leave them alone in basements and crawl spaces.
Jumping Spiders
Jumping spiders are compact, alert, and oddly charismatic. They’re easy to recognize by their two large, forward-facing eyes, which give them an almost face-like appearance. They actually have eight eyes total, providing nearly 360-degree vision. Many species are covered in iridescent scales or colorful hairs.
Unlike web-building spiders, jumping spiders are daytime hunters that stalk and pounce on prey like ants and fruit flies. They use silk only as a safety line when they leap, or to build small sac-like retreats for resting and molting. Indoors, you’ll often spot them on sunny windowsills and walls. The zebra jumper is one of the most common indoor species: black with three or four pairs of white marks along its abdomen, and a body length under a quarter inch.
Wolf Spiders
Wolf spiders are the ones that startle people. They’re fast, ground-dwelling hunters that can be surprisingly large, with body lengths ranging from a quarter inch to a full inch depending on the species. Females tend to be noticeably bigger than males. They’re usually gray, brown, or tan with dark stripes along the body.
Their eye arrangement is distinctive: four small eyes in a bottom row, two large eyes in the middle row facing forward, and two medium eyes on top. Those large middle eyes give them excellent vision for chasing down prey at speed. Wolf spiders don’t build webs. They either actively pursue insects or sit motionless and ambush whatever crawls within reach. They typically enter homes by accident while hunting, especially in fall when temperatures drop. Despite their intimidating size, North American wolf spider bites are harmless.
Yellow Sac Spiders
Yellow sac spiders are pale, cream-to-light-yellow spiders about three-eighths of an inch long. They’re active at night and are most often spotted walking across walls and ceilings in search of prey. During the day, they hide in silken tubes or sacs built in the upper corners of rooms, where walls meet ceilings.
These spiders likely account for more human bites than any other type, simply because they wander across beds and clothing at night. The bite is initially painful with a burning sensation lasting up to an hour. Redness, swelling, and blistering can develop over the next several hours. Some people experience mild systemic symptoms like fever, muscle cramps, or nausea. The effects are far less serious than those of a brown recluse or black widow, and bites typically heal without scarring.
Other Common Indoor Species
Funnel weaver spiders build sheet-like webs with a funnel-shaped retreat where they wait for vibrations from trapped prey. Indoors, they favor dimly lit spaces like storage boxes, closets, and basement corners. They’re medium brown with lighter chevron markings on the abdomen. Running crab spiders and ground spiders (sometimes called mouse spiders) occasionally wander inside while hunting. These are small, fast spiders that don’t build prey-catching webs and typically have no interest in staying indoors long-term.
Spiders Worth Identifying Carefully
Two species in North America can cause serious harm: the brown recluse and the black widow.
The brown recluse is light tan to dark brown, about half an inch long, with long, delicate legs. Its most reliable identifying feature is a violin-shaped dark marking behind its eyes, with the “neck” of the violin pointing toward the abdomen. Critically, it has only six eyes arranged in three pairs (a semicircle), while nearly all other house spiders have eight. Brown recluses are secretive and nocturnal, hiding in undisturbed areas like cardboard boxes, closets, and behind furniture. Their bite kills surrounding tissue, creating a wound that can take six to eight weeks to heal and sometimes requires skin grafts.
The black widow is glossy black and globular, never hairy. Females are about an inch and a half long with legs extended, and the key marking is a reddish hourglass shape on the underside of the abdomen. Black widows hang belly-up in irregular webs and rarely leave them. They’re generally considered the most venomous spider native to North America, though bites are uncommon because the spiders are reclusive and non-aggressive.
How to Tell Spiders Apart Quickly
You don’t need to memorize species names. A few quick observations narrow things down fast:
- Web or no web: If it’s sitting in a web, it’s likely a cobweb spider, cellar spider, or funnel weaver. If it’s running freely on a wall or floor, think jumping spider, wolf spider, yellow sac spider, or ground spider.
- Eyes: Two big forward-facing eyes mean a jumping spider. Two large eyes in the middle of a stacked arrangement suggest a wolf spider. Six eyes in three pairs (not eight) point to a brown recluse.
- Body shape: A round, glossy black abdomen suggests a black widow. A peanut-shaped body with extremely long, thin legs is a cellar spider. A compact, fuzzy body with short legs is likely a jumping spider.
- Location: Basements and cellars favor cellar spiders and funnel weavers. Ceilings and upper wall corners are yellow sac spider territory. Sunny windowsills attract jumping spiders. Garages, sheds, and undisturbed storage areas are where brown recluses and black widows tend to hide.
Keeping Spider Numbers Down
Most indoor spiders are beneficial because they eat flies, mosquitoes, and other pests. But if you’d rather not share your space, the most effective approach targets what draws them inside in the first place.
Seal cracks and gaps around windows, doors, and basement walls with caulk. Repair torn window screens and replace worn weather stripping. These small fixes eliminate the most common entry points. Outdoor lighting attracts the insects that spiders feed on, so switching to yellow sodium vapor bulbs or motion-activated lights reduces the buffet near your doors.
Inside, regular vacuuming disrupts webs, removes egg sacs, and eliminates the small insects spiders prey on. Pay attention to tucked-away spots under furniture and behind appliances. Decluttering basements, attics, and storage rooms removes the dark, undisturbed hiding spots spiders prefer. Storing items in sealed bins elevated off the floor makes it harder for spiders to set up shop. Trimming vegetation and clearing debris near your home’s exterior also reduces the population of spiders working their way toward your walls.