Common House Spider: Identification, Habits & Bite Safety

Common house spider identification, quick visual answer

A common house spider is small, tan-brown, and almost spherical at the abdomen. The body measures 5–8 mm in adult females and 3–5 mm in males. The abdomen is bulbous and sits high above a small cephalothorax, producing a marble-on-legs silhouette that’s distinct from longer-bodied spiders. Color ranges from pale tan and yellowish-brown to dark brown, often with a faint chevron, mottled, or speckled pattern across the top of the abdomen.

Behavior is the second giveaway. House spiders sit motionless and upside-down in the upper part of a tangled cobweb, often tucked into a ceiling corner or against the back of a piece of furniture. When the web is disturbed, the spider drops out on a silk line and plays dead on the floor for several minutes before climbing back up. They are not aggressive and do not actively pursue intruders, including humans.

The web is the third tell. House spider webs are messy 3D tangles with no geometric pattern, what people casually call “cobwebs.” The web has two functional zones: the upper retreat where the spider waits, and the lower sticky gum-foot threads stretched down to the floor or nearest surface, which snare walking insects. For broader comparisons across spider families, see the spider identifier hub.

American house spider vs common house spider, clearing up the confusion

The phrase “common house spider” means different species on different sides of the Atlantic. In the US, it almost always refers to Parasteatoda tepidariorum, also called the American house spider, a small tan-brown cobweb spider in family Theridiidae. In the UK and Ireland, the same phrase usually refers to Tegenaria domestica, a larger brown funnel weaver in family Agelenidae. They are different families, different shapes, and different behaviors despite sharing the name.

Practically, if you’re reading from a US address, every reference on this page to “common house spider” means Parasteatoda tepidariorum. If you’re in the UK or rural Pacific Northwest, you may well be looking at a Tegenaria. The Tegenaria-group spiders are closely related to the hobo spider, see our hobo spider guide for the funnel-weaver side of the family.

Parasteatoda tepidariorum, full species profile

Parasteatoda tepidariorum is the default indoor spider across the United States and most of the rest of the inhabited world. The species was originally described from Europe but has been carried by humans on ships, trucks, and household goods to every continent except Antarctica. Today it’s the most cosmopolitan spider on Earth and the most likely indoor spider you’ll see from Florida to Alaska to Australia.

Body length is 5–8 mm in adult females and 3–5 mm in males, females are noticeably larger and the ones people usually see. The abdomen is the diagnostic feature: bulbous, nearly spherical, set high above the cephalothorax, and patterned with a faint chevron, mottling, or speckled appearance. Color varies from pale tan and yellow-brown to dark brown or gray-brown. Even within a single web you may see several individuals at different color shades, color is not a reliable species feature on its own.

Legs are slim and lightly banded with alternating pale and dark segments. Leg length is roughly 1.5–2 times body length, far shorter than a cellar spider’s thread-thin legs but slightly longer than a wolf spider’s legs relative to body size. Eight small eyes sit in two rows of four at the front of the cephalothorax. The fangs (chelicerae) are short and point downward.

Habitat is essentially anywhere undisturbed and dry: ceiling corners, garages, sheds, basements, attics, window frames, behind furniture, and outdoor surfaces like eaves and wood siding. Parasteatoda is exceptional at coexisting with humans, it tolerates a wide range of temperatures and humidity, takes whatever prey is available, and produces enough offspring to maintain populations indoors year-round. Lifespan is typically 1–1.5 years per adult.

Tegenaria domestica, the UK common house spider

Tegenaria domestica is the species British and Irish readers usually have in mind when they say “common house spider.” It’s a brown funnel weaver in family Agelenidae, the same family as the hobo spider, and looks very different from the American Parasteatoda. The body is longer and flatter, the legs are visibly banded and built for sprinting, and the web is a flat sheet with a tubular funnel retreat rather than a 3D tangle.

Body length is 7–12 mm in females, 6–9 mm in males. The abdomen is long and oval with a herringbone or chevron pattern in shades of brown and tan. The cephalothorax is robust with two dark longitudinal bands. Legs are long and clearly banded, often spanning 30–50 mm in adult specimens. The eight eyes are in two roughly straight rows.

Web type is the easiest separator from Parasteatoda. Tegenaria domestica builds a flat horizontal sheet of tightly woven silk, with a tubular funnel in one corner where the spider waits. When an insect lands on the sheet, the spider sprints out from the funnel, grabs the prey, and drags it back into the tube. The web has no sticky threads, Tegenaria catches prey by speed, not glue. See the hobo spider page for the related but slightly more notorious member of the same family.

In the US, Tegenaria domestica is found mainly in the Pacific Northwest (Washington, Oregon, British Columbia) and occasionally in other parts of the country where European immigrants and shipping introduced it. The giant house spider (Eratigena atrica, formerly Tegenaria duellica) is a related and larger species common in the same region. Like all funnel weavers, Tegenaria domestica is harmless to people, bites are rare and produce only minor local symptoms.

House spider web, the tangled cobweb explained

A common house spider web is a messy, irregular 3D cobweb built in a corner. It looks chaotic, but the structure has two functional zones built into it. The upper zone is the retreat, a denser tangle where the spider hangs upside-down and waits. The lower zone is a screen of vertical sticky gum-foot threads stretched down to the floor or surface beneath, designed to snare walking prey.

Each gum-foot thread is coated for the last few millimeters at the bottom with a glue droplet. When a walking insect like a beetle, ant, or small roach touches the droplet, the thread breaks at the bottom and recoils upward like a snare, lifting the prey clear of the ground and into the tangle above. The trapped insect dangles helplessly while the spider descends, throws sticky silk over the prey to immobilize it, and delivers a bite. Prey is then hauled into the upper retreat for feeding.

Gum-foot threads are a Theridiidae family signature, black widows and Steatoda false widows use the same system. The technique works for both flying and walking prey, which is why theridiid cobweb spiders are so successful as generalist indoor predators. Aesthetically, the gum-foot threads are why old house spider webs look like they have small spots or beads suspended at floor level: those are the unused glue droplets waiting for prey to walk through.

House spider webs are not maintained. When a web becomes too cluttered with debris or damaged by traffic, the spider abandons it and builds a new one in a nearby corner. Old abandoned webs accumulate dust and are what most homeowners think of as “cobwebs”, they often persist for months after the spider has moved on or died.

House spider anatomy

Common house spider anatomy is built around the sit-and-wait theridiid lifestyle. The abdomen is large and bulbous to hold reproductive organs and silk glands. The cephalothorax is small and oval. The legs are modest in length, not the long thread-legs of a cellar spider, not the robust running legs of a wolf spider, but slim, banded, and well-suited to climbing on and within a 3D tangled web.

Two anatomical features are diagnostic for the family Theridiidae and reliable for distinguishing common house spiders from look-alikes. First, the abdomen is rounded and set high above the cephalothorax, producing the “marble on legs” silhouette. Second, the spinnerets produce gum-foot threads with terminal glue droplets, visible at the bottom of an established web as small specks suspended at floor level. Both features are shared with black widows and Steatoda false widows because they’re all in the same family.

Common house spider life cycle

Common house spiders complete their life cycle in about a year in heated indoor environments. The cycle goes: mating, egg sac construction, egg incubation, spiderling emergence, juvenile molts, sub-adult, and finally adulthood with continued reproduction. Females outlive males in every cohort. Reproduction is continuous enough indoors that most homes host overlapping generations year-round.

Egg production is the feature that makes Parasteatoda so successful. A single female lays 100–400 eggs per sac and produces multiple sacs over her adult life. Lab studies have documented up to 17 sacs in optimal conditions, though 4–9 sacs is more realistic for an indoor female with normal prey supply. Each sac is a tan or pale-brown sphere about 6–9 mm across, suspended in the web above the spider’s resting position. See the egg sac section below for identification and removal advice.

Spiderlings emerge from the sac after 7–10 days of incubation, molt once inside the sac, then chew through the silk and disperse. Some balloon away on silk threads carried by air currents; others walk to nearby corners and start their own webs. Mortality is high in the first few weeks, most spiderlings are eaten by larger spiders, ants, or environmental hazards before reaching their second molt. The handful that survive reach sexual maturity 3–6 months later.

House spider behavior

Common house spiders are sit-and-wait predators with a small behavioral repertoire built around the web. The spider spends 90% of its time hanging upside-down in the upper retreat of the cobweb. Movement is minimal, a few small adjustments to silk threads, occasional repair work, and dashes to wrap prey. The economy of motion is part of why they can survive on relatively little food.

Prey capture follows a stereotyped sequence. The spider feels prey contact through web vibrations, descends along a silk dragline to the trapped insect, throws several loops of sticky silk over the prey to immobilize it, then delivers a venomous bite. For larger prey like wasps or small roaches, the spider may drop the wrapped bundle to the floor briefly while venom takes effect, then haul it back up to feed. The wrap-and-drop technique lets a small spider safely subdue prey several times its own size.

Defense is dropping out of the web. When the cobweb is disturbed by a duster, a passing animal, or a human touch, the spider releases its hold and falls to the floor on a silk line. On the ground it plays dead for several minutes, legs curled inward, motionless, before slowly walking back up the silk to the web. This drop-and-play-dead response is why house spiders almost never bite people: by the time you’ve disturbed the web, the spider is already on the floor pretending to be dead.

Cannibalism happens occasionally. A small wandering male approaching a female’s web is generally safe if he plucks the silk in a species-specific courtship rhythm before approaching. Males who skip the rhythm may be treated as prey. Adult-on-adult cannibalism between females in adjacent webs is rare but recorded. Spiderlings are routinely eaten by other spiders, including older Parasteatoda siblings, high mortality is part of why each female produces hundreds of eggs.

House spider as pest control

A common house spider is, biologically, free pest control. Each adult female in a well-stocked corner consumes dozens of small insects per week, flies, mosquitoes, fruit flies, gnats, small moths, ants, and even small roaches that walk into gum-foot threads. Over a 1-year adult lifespan, a single house spider can eat thousands of pest insects without any input from the homeowner.

The pest profile of a Parasteatoda diet skews toward the bugs most homeowners actually want gone. Mosquito predation is meaningful in garages and basements where mosquitoes overwinter. Fruit fly and gnat catches accumulate in kitchen and bathroom corners. Small roach nymphs that wander out of harborages can be snared by gum-foot threads at floor level, a particular benefit in older homes with mild roach pressure. Multiply this by the dozens of spiders in an undisturbed garage and the pest reduction is real.

The trade-off is the visible web and occasional spider sighting. Cobwebs in ceiling corners are universally considered unsightly, and house spiders in shower stalls or above beds make some people uncomfortable regardless of their actual harmlessness. For most homeowners, the answer is a tolerance gradient: leave them alone in garages, basements, attics, and outdoor sheds; remove them from bedrooms and immediate living areas. For removal technique that doesn’t harm the spider, see our safe spider removal guide.

Where common house spiders live

Common house spiders are habitat generalists with a strong preference for undisturbed indoor and near-indoor spaces. The species’ success at colonizing human structures is one of the most impressive in spider biology, Parasteatoda tepidariorum now lives on every continent except Antarctica, almost entirely thanks to human transport. Outdoor populations exist but are usually concentrated near buildings.

Two locations deserve extra mention. Garages routinely host the highest house spider density per square foot of any indoor space, sometimes dozens of individuals across all the corners, door tracks, and shelving. Basements run a close second when prey is available. The pattern is the same in both: stable temperature, abundant corners, low disturbance, and steady traffic of flying and walking insects through door gaps and vents.

House spider vs other indoor spider look-alikes

Common house spiders are routinely confused with several other indoor spiders, some genuinely related and some only similar in size or location. The most important confusion is with Steatoda false widows (same family, very similar body shape) and with juvenile black widows (also same family, similar size). The table below covers the most common look-alikes and the features that separate them.

Three quick field tests. First, check for a red marking on the underside of the abdomen, only true widows have it; a house spider, false widow, or cellar spider does not. Second, look at the web, a tangled 3D cobweb with gum-foot threads going down to the floor is theridiid (house spider, false widow, or widow); a flat sheet with a funnel retreat is agelenid (hobo, Tegenaria, giant house spider). Third, look at leg length relative to body, thread-thin legs 5+ times body length means cellar spider, not house spider. For extra comparisons see the cellar spider page, the jumping spider guide, and our wolf spider size reference.

House spider vs Steatoda (false widow), the close-relative confusion

The single most editorially important comparison on this page is between the common house spider and the Steatoda false widows. Both genera are in family Theridiidae, both have nearly identical body shape, both build the same tangled cobweb with gum-foot threads, and both share habitat indoors. The differences come down to color and, at the dangerous end of the family, the true black widows in genus Latrodectus.

The American house spider is one of the easiest-to-confuse harmless species in the country because of this family resemblance. A homeowner who finds a glossy dark-brown spherical spider in a basement cobweb and assumes it’s a black widow is usually looking at either Parasteatoda tepidariorum (lighter brown, faint chevron) or Steatoda grossa (darker, glossier, pale band). Both are harmless. The true widow has a bright red hourglass on the underside that none of the harmless look-alikes carry. For confirmed widow identification and bite safety, see our black widow identification page.

Steatoda nobilis is worth a separate note. This European species has expanded its range across the UK and parts of California in recent decades and is the false widow most likely to deliver a noticeable bite (mild local pain, occasional blistering). It is still vastly less dangerous than a true widow. For the standard US homeowner, the practical takeaway is: glossy brown spherical spider with a pale band on top of the abdomen and no red marking on the underside is a false widow, not a true widow, and almost certainly harmless.

House spider venom and bite safety

Common house spider venom is mild and not medically significant for healthy adults. The CDC does not list Parasteatoda tepidariorum as a medically important species, and university extension services across the US classify the species as harmless. The active components of the venom are calibrated for small insect prey, flies, mosquitoes, gnats, and have little physiological effect on mammals at the doses a tiny spider can deliver.

Bites are extremely rare. Common house spiders almost always drop out of the web and play dead when disturbed rather than biting. The few documented bites occur when the spider is pressed against skin inside clothing, bedding, or under a glove. When a bite does happen, it feels like a mild pinprick and produces a small red mark with brief itching that resolves within hours. No special first aid is needed, wash the area with soap and water, ice if itchy, and move on.

Watch out for misattribution. Welts blamed on common house spiders are far more often bed bug, flea, or mosquito bites, those are the genuinely common bite causes in homes and are easy to mistake for spider bites if you find a spider in the same room. For differentials and how to distinguish bite types by location on the body and progression over time, see the bug bite identification guide. For comparison with spiders that do warrant medical caution, see black widow identification and brown recluse identification.

House spider egg sac identification

House spider egg sacs are spherical balls of dense silk, 6–9 mm in diameter, tan to pale brown. They’re suspended in the upper part of the web near where the female rests, often visible from below as small pale spheres against the darker tangle. Multiple sacs may be present in a single web from successive clutches over a female’s 1-year adult life. Each sac holds about 100–400 eggs.

The texture is papery and slightly translucent. Held to a strong light you can sometimes see the dark mass of eggs inside fresh sacs, or the slightly empty appearance of sacs from which spiderlings have already emerged. Old empty sacs persist in webs for months and are sometimes mistaken for new ones, look for the exit hole or the dehydrated, collapsed shape to identify empty sacs.

Whether to remove egg sacs depends on tolerance for the local house spider population. If you want to keep the natural pest control going, leave the sacs alone, they hatch in 1–3 weeks and the spiderlings disperse within a few more days. If you want to reduce indoor numbers, removing egg sacs before they hatch is the single most effective action you can take (each sac is 100–400 future spiders). Knock the sac down with a broom or vacuum nozzle. The sacs are not dangerous to touch and spiderlings inside cannot bite even after emergence. Adult Parasteatoda are similarly harmless, there’s no chemical product needed at any step of this.

House spider myths debunked

Common house spiders attract a lot of mythology because they’re ubiquitous, visible, and in the same family as black widows. Here are the most common false beliefs and what the science actually says.

Should you keep house spiders around?

For most homeowners, yes, common house spiders are one of the most useful small predators you can host indoors. They eat flies, mosquitoes, gnats, small moths, ants, and small roaches at a meaningful rate; they’re harmless to people and pets; and they require zero input or maintenance. Leaving them alone in garages, basements, attics, and undisturbed ceiling corners is the simplest form of biological pest control available.

There are reasonable exceptions. Bedrooms and immediate living spaces are fair game for removal if a visible spider above your bed makes sleep difficult. People with severe arachnophobia don’t benefit from forced exposure to webs in living rooms. Some individuals have mild allergic sensitivity to spider silk or spider feces, though this is genuinely rare. And if a guest is staying who would not appreciate the biology lecture, a quick relocation is fine.

When you do remove a house spider, the cup-and-card method works perfectly: a clear cup over the spider, a stiff card slid underneath, carried outside to a sheltered spot like an outdoor windowsill or under an eave. Don’t crush it on the wall, you’re killing a free pest control agent that wasn’t going to harm you. For full removal technique including web removal and prevention, see our humane spider removal guide. For comparison with other harmless indoor spiders worth keeping around, see the cellar spider and jumping spider pages.

Reducing indoor house spider populations

If you want fewer common house spiders indoors, the durable strategy is reducing the prey base. House spiders are there because flying and walking insects are there. Cut the insect supply and the spider population drops within weeks because females cannot produce sacs without food, and individuals starve or relocate when prey runs out.

Specific steps that work. Install or replace door sweeps on all exterior doors, gaps under doors are the single biggest entry point for small flies and walking insects. Repair window screens with any holes or tears. Fix damp areas in basements and bathrooms (humidity attracts small flies and other prey). Manage ant trails and small roach pressure with bait stations rather than aerosol sprays, which kill the visible spiders but not the underlying prey supply that draws new ones in. Clean drains regularly to eliminate fruit fly and drain fly populations that feed indoor house spider colonies.

Direct spider control is the second tier. Remove webs and egg sacs with a vacuum or broom on a regular schedule, once a week in problem areas. Each web removal forces the spider to rebuild, which costs energy and reduces successful clutches. Each egg sac removal eliminates 100–400 future spiders. Declutter storage areas like garages and basements that provide undisturbed web sites. None of this requires chemical pesticides, house spiders are easier to manage with vacuum and prey-base control than with sprays.

Realistic expectations: you will not eliminate house spiders entirely from any structure with normal insect traffic. The species is too widespread, too well-adapted to indoor life, and too good at producing eggs for that. Acceptance of a small resident population in garages, basements, and outdoor-adjacent areas is the most sustainable outcome, with active removal limited to immediate living spaces.

Pest control disclaimer. Photo-based identification can help, but it is not always perfect. For dangerous spiders, large infestations, or anything you are unsure about, contact a licensed pest control professional.