Common House Spider: Identification, Habits & Bite Safety

Common house spider identification, quick visual answer

A common house spider is small and tan-brown, with an almost round abdomen. Adult females are 5–8 mm long, and males are 3–5 mm. The bulging abdomen sits high above a small front body part, which gives it a marble-on-legs shape unlike longer-bodied spiders. Color ranges from pale tan and yellow-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 clue. House spider webs are messy 3D tangles with no pattern, what most people call “cobwebs.” The web has two working parts. The spider waits in the upper retreat. Below it, sticky gum-foot threads stretch down to the floor or the nearest surface to snare walking insects. For comparisons across spider families, see the spider identifier hub.

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

One name, two spiders. Which one people mean depends on where they live. In the US, “common house spider” almost always means Parasteatoda tepidariorum, the small tan-brown cobweb spider also called the American house spider. It sits in the family Theridiidae. In the UK and Ireland, the same phrase usually means Tegenaria domestica, a larger brown funnel weaver in the family Agelenidae. So the two share a name and very little else. They belong to different families, they are built differently, and they behave differently.

So here is the shorthand for the rest of this page. If you are reading from the US, “common house spider” means Parasteatoda tepidariorum every time. If you are in the UK, or in the rural Pacific Northwest, you may well have a Tegenaria instead. 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 in the United States, and in most of the inhabited world too. Older field guides file it under Achaearanea tepidariorum, which is the same spider under its previous genus, so do not let the mismatch worry you. Where it started is genuinely unsettled. Some sources place its native range in Asia, others in the Neotropics, and the question is still open. What is not in doubt is how it got everywhere else. People carried it, on ships, in trucks, and inside household goods. It now lives on every continent except Antarctica. That makes it the most widespread spider on Earth, and the one you are most likely to meet indoors from Florida to Alaska.

Size, colour, and markings

Adult females are 5–8 mm long and males 3–5 mm, so the females are clearly larger, and they are the ones people usually see. The abdomen is the key feature. It is bulging and nearly round, sits high above the front body part, and has a faint chevron, mottled or speckled pattern. Color ranges from pale tan and yellow-brown to dark brown or gray-brown. Even in one web you may see spiders of several shades, so color alone will not tell you the species.

Leg colour is a useful secondary check. Penn State Extension describes females with yellow legs ringed darker at each joint, and males with orange legs. Some individuals also carry a triangular black spot on top of the abdomen. None of these is diagnostic on its own, but together they build the picture.

Legs and eyes

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.

Where it lives, and for how long

It will settle almost anywhere dry and undisturbed. Ceiling corners are the classic spot. Garages, sheds, basements, attics, window frames, and the space behind furniture all work just as well, and so do eaves and wood siding outside. Parasteatoda lives alongside people better than almost any other spider. It copes with a wide range of temperature and humidity, it eats whatever walks into the web, and it breeds fast enough to hold a population indoors all year. Adults usually live one to one and a half years.

Tegenaria domestica, the UK common house spider

Tegenaria domestica is what British and Irish readers usually mean by “common house spider.” It is a brown funnel weaver in the family Agelenidae, the same family as the hobo spider. Next to the American Parasteatoda it looks like a different animal. The body is longer and flatter. The legs are clearly banded and built for sprinting. Instead of a 3D tangle, it spins a flat sheet with a tube-shaped funnel retreat at one edge.

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 turns up mainly in the Pacific Northwest: Washington, Oregon and British Columbia. It also appears elsewhere, wherever European shipping and settlers brought it. A larger relative shares that region, the giant house spider (Eratigena atrica), which older books call Tegenaria duellica. Like every funnel weaver, Tegenaria domestica is harmless. Bites are rare and cause nothing worse than brief local soreness.

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.

How a gum-foot trap works

Each gum-foot thread has a glue droplet on its last few millimeters. When a walking insect like a beetle, ant or small roach touches the droplet, the thread breaks at the bottom and springs upward like a snare. It lifts the prey off the ground and into the tangle above. The trapped insect dangles while the spider climbs down, throws sticky silk over it and bites. Then the spider hauls the prey up into its retreat to feed.

The silk is the “ecribellate” kind: the spider makes it sticky with wet glue droplets, not by combing out dry, fluffy fibers. Gum-foot threads are a signature of the cobweb spider family (Theridiidae). Black widows and Steatoda false widows use the same system. It catches both flying and walking prey, which is why cobweb spiders do so well as all-round indoor predators. Gum-foot threads are also why old house spider webs look like they have small beads hanging near the floor. Those are unused glue droplets, still waiting for prey to walk through.

Why house spiders keep abandoning webs

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 one job: sitting still in a web and waiting. The abdomen is large and bulbous, because it holds the reproductive organs, the silk glands, and the book lungs the spider breathes through. Ahead of it sits a small oval cephalothorax carrying the eyes, the fangs, and the legs. Those legs are middling in length. They are nothing like the thread-legs of a cellar spider, and nothing like the running legs of a wolf spider. Instead they are slim and banded, and they suit climbing around inside a 3D tangle.

Two features mark out the family Theridiidae, and both are easy to check. First, look at the silhouette. The abdomen is round and rides high above the cephalothorax, which gives the spider its “marble on legs” outline. Second, look at the bottom of the web. The spinnerets lay down gum-foot threads tipped with glue droplets, and in an old web you can see them as tiny specks hanging at floor level. Black widows and Steatoda false widows share both features, because all three belong to the same family.

Common house spider life cycle

In a heated house, a common house spider runs through its whole life cycle in about a year. The stages go in order: mating, then the egg sac, then incubation, then spiderlings, then a run of juvenile molts, then a sub-adult stage, and finally adulthood. Each molt produces a new instar, and a house spider passes through roughly six or seven of them before it can breed. Females outlive males in every cohort. Indoors the breeding barely pauses, so most homes hold two or three overlapping generations at once.

Egg laying is what makes Parasteatoda so successful. A single female lays 100–400 eggs per sac and makes several sacs over her adult life. Lab studies have recorded up to 17 sacs in ideal conditions, though 4–9 sacs is more realistic for an indoor female with a normal food supply. Each sac is a tan or pale brown ball about 6–9 mm across, hanging in the web above where the spider rests. See the egg sac section below for identification and removal advice.

Spiderlings hatch after 7–10 days. They molt once inside the sac, then chew through the silk and spread out. Some drift away on silk threads carried by air currents, while others walk to nearby corners and start their own webs. Most die in the first few weeks. Larger spiders, ants and other hazards kill the majority before their second molt. The few that survive become adults 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.

How it catches prey

Prey capture follows the same steps every time. The spider feels prey hit the web through the vibrations. It drops down a silk line to the trapped insect and throws several loops of sticky silk over it to pin it. Then it bites. With larger prey, like a wasp or a small roach, the spider may drop the wrapped bundle to the floor for a moment while the venom works, then haul it back up to feed. This wrap-and-drop trick lets a small spider safely handle prey several times its own size.

Why it drops out of the web

To defend itself, the spider drops out of the web. When something disturbs the cobweb, such as a duster, an animal or a hand, the spider lets go and falls to the floor on a silk line. On the ground it plays dead for several minutes, legs curled in and perfectly still, then slowly climbs the silk back to the web. This is why house spiders almost never bite people. By the time you have disturbed the web, the spider is already on the floor pretending to be dead.

How often they eat each other

Cannibalism does happen, though less often than the reputation suggests. A small male walking onto a female’s web is usually safe, provided he plucks the silk in the courtship rhythm of his species first. Skip the rhythm and he risks being read as prey. Females in neighbouring webs eat each other only rarely, but it has been recorded. Spiderlings have it worst. Other spiders eat them constantly, older siblings included, and that heavy loss is exactly why each female lays hundreds of eggs.

House spider as pest control

A common house spider is, in effect, free pest control. Each adult female in a busy corner eats dozens of small insects a week. Her menu includes flies, mosquitoes, fruit flies, gnats, small moths, ants and even small roaches that walk into the gum-foot threads. Over an adult life of about a year, one house spider can eat thousands of pests without any help from you.

What Parasteatoda eats lines up neatly with what people want rid of. In garages and basements, where mosquitoes shelter over winter, it takes a real share of them. In kitchen and bathroom corners, fruit flies and gnats pile up in the web. Small roach nymphs that wander out of a hiding place get caught on the gum-foot threads near the floor, which helps in older homes with mild roach pressure. Now multiply that by the dozens of spiders living in an undisturbed garage. The dent they make is real.

The cost is the web, and the odd spider you did not want to see. Nobody likes a cobweb in a ceiling corner, and a spider in the shower or over the bed unsettles people whether or not it can hurt them. So most households land on a sliding scale rather than a rule. Leave them alone in garages, basements, attics, and sheds. Move them out of bedrooms and the rooms you actually sit in.

Where common house spiders live

Common house spiders will live almost anywhere, but they clearly prefer quiet corners in and around buildings. Few spiders have moved into human spaces so completely. Parasteatoda tepidariorum now lives on every continent except Antarctica, and people did nearly all the carrying. Outdoor populations do exist. They just tend to sit close to a wall.

Two places deserve extra mention. Garages often have more house spiders per square foot than any other indoor space, sometimes dozens spread across corners, door tracks and shelves. Basements come a close second when there is prey. The pattern is the same in both: a steady temperature, plenty of corners, little disturbance, and a stream of flying and walking insects coming in through door gaps and vents.

House spider vs other indoor spider look-alikes

Plenty of indoor spiders get called common house spiders. Some really are close relatives. Others just happen to be the same size or turn up in the same corner. Two mix-ups matter more than the rest. One is with Steatoda false widows, which sit in the same family and share the body shape almost exactly. Another is with young black widows, also same family and much the same size. Use the table below, which sorts them by the features that actually separate them.

Three quick field tests settle it. First, check the underside of the abdomen for a red mark. Only true widows have one, while house spiders, false widows and cellar spiders do not. Second, look at the web. A tangled 3D cobweb with gum-foot threads down to the floor belongs to the cobweb family: a house spider, false widow or widow. A flat sheet with a funnel belongs to the funnel weavers: a hobo, Tegenaria or giant house spider. Third, compare leg length with body length. Thread-thin legs 5 or more times the body length mean a cellar spider, not a house spider. For more 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

This is the comparison that matters most on the page. Common house spiders and Steatoda false widows sit in the same family, Theridiidae. Their body shapes are almost identical. They build the same tangled cobweb with the same gum-foot threads, and they live in the same indoor corners. Colour is what separates them. At the far end of that family sit the true black widows, genus Latrodectus, and those are a different matter entirely.

That family resemblance makes the American house spider one of the most misidentified harmless spiders in the country. Picture the usual scene. Someone finds a glossy dark spider with a round body in a basement cobweb and calls it a black widow. Nearly always it is one of two others. Parasteatoda tepidariorum is the lighter brown one with a faint chevron. Steatoda grossa is darker and glossier with a pale band. Both are harmless. Only a true widow carries the bright red hourglass underneath, and neither look-alike has it. For confirmed widow identification and bite safety, see our black widow identification page.

Steatoda nobilis deserves its own note. This European spider has spread across the UK and into parts of California over the last few decades. Of all the false widows, it is the one most likely to give a bite you notice, usually mild local pain and now and then a small blister. Even so, it is far milder than a true widow.

For most US readers the rule is short. A glossy brown round-bodied spider with a pale band on top of the abdomen and no red mark underneath is a false widow. It is not a true widow, and it is almost certainly harmless.

House spider venom and bite safety

Common house spider venom is mild, and no health authority treats it as significant. The CDC does not list Parasteatoda tepidariorum among medically important species, and US extension services class it as harmless. Technically the venom is neurotoxic, like that of other cobweb spiders. That word alarms people, so it is worth being clear about scale. The venom is tuned for flies, mosquitoes, and gnats. A spider this small cannot deliver a dose that does much to a mammal.

What a house spider bite actually does

Bites are genuinely rare, because the spider runs rather than fights. Penn State Extension records what happens on the rare occasions someone is bitten: a red mark, pain that builds for about an hour, then soreness lasting somewhere between 4 and 24 hours. Nothing blisters, and nothing breaks down. Wash it, and leave it alone.

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.

Be careful about blame, though. Welts pinned on common house spiders usually come from something else. Bed bugs, fleas, and mosquitoes cause nearly all the bites people get at home. Finding a spider in the same room feels like proof, and it is not. 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, and Penn State Extension records females producing twelve or more sacs across a lifetime. One spider in one ceiling corner can therefore account for a few thousand 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 how many house spiders you are happy to live with. To keep the free pest control going, leave the sacs alone. They hatch in 1–3 weeks, and the spiderlings spread out within a few more days. To cut indoor numbers, removing egg sacs before they hatch is the most effective step you can take, since each sac holds 100–400 future spiders. Knock the sac down with a broom or a vacuum nozzle. The sacs are safe to touch, and the spiderlings inside cannot bite, even after they hatch. Adult house spiders are just as harmless, so you need no chemical product at any step.

The house spider is a laboratory model animal

Here is something almost nobody knows about the spider in the ceiling corner. Parasteatoda tepidariorum is a working lab animal, used in research the way the fruit fly and the lab mouse are. Biologists keep colonies of it, and its full genome has been sequenced and stored in the NCBI reference database.

Researchers picked it for a specific reason. Spiders sit in Chelicerata, one of the four great branches of the arthropods, and that branch is the one furthest from insects. So if you want to know which parts of animal development are ancient and shared, and which parts insects invented on their own, you need something outside the insect line to compare against. This spider fills that role.

It also happens to be easy to keep. Females produce a fresh batch of eggs every four to six days, the eggs hatch in about a week at 25°C, and the young reach adulthood in two to three months. That short cycle is exactly what a genetics lab needs.

The work has produced real findings, too. Sequencing the genome revealed a whole-genome duplication far back in the arachnid family tree, which means an early spider ended up with two copies of every gene. Studies of embryos have also shown that spiders build their body segments in a different way from insects. None of that changes how you deal with a cobweb. But it does mean the animal in your garage is one of the best-understood spiders on Earth.

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.

• Myth 1

  Myth: “House spiders kill more pests than they bring into the home.”

  Truth: Misleading. House spiders do not 'bring' pests at all. They only show up because pests are already there. They really do eat flies, mosquitoes, fruit flies and small roaches at a useful rate, dozens per spider per week in busy corners. The pest control is real, but it cannot make up for an underlying pest problem.

• Myth 2

  Myth: “You should kill house spiders on sight.”

  Truth: False. Common house spiders are not medically significant or aggressive, and they are among the most useful small predators in a home. Most spider experts and university extension services say to leave them alone in quiet corners. If one is somewhere truly in the way, move it with a cup and a card.

• Myth 3

  Myth: “House spiders bite people in their sleep.”

  Truth: False. Bites are extremely rare and almost always happen because the spider was pressed against skin inside clothing or bedding. House spiders sit and wait for prey, and when disturbed they drop out of the web and play dead. Mystery bumps blamed on house spiders are usually bed bug, flea or mosquito bites. See our bug bite identification page to tell them apart.

• Myth 4

  Myth: “Only dirty homes have house spiders.”

  Truth: False. House spider numbers follow their insect prey, not dirt. Spotless homes with good door sweeps still have house spiders, because tiny flies, gnats and other prey get in through any open door. On the other hand, a damp home with pest problems has far more spiders, however hard you clean.

• Myth 5

  Myth: “A house spider in a web on the ceiling is a black widow.”

  Truth: False in nearly every case. Black widows are glossy jet-black with a bright red hourglass on the underside of the abdomen. American house spiders are tan to dark brown, with a faint chevron pattern and no red mark. Both belong to the cobweb family (Theridiidae), so they build similar tangled webs, but the color difference is obvious in good light.

• Myth 6

  Myth: “House spiders can survive without food for years.”

  Truth: Exaggerated. Adult house spiders can survive several weeks to a few months without food in mild conditions, especially if they have water. Surviving for years without food has never been recorded for Parasteatoda tepidariorum. The myth probably comes from old, dusty webs mistaken for active ones long after the spider has gone.

• Myth 7

  Myth: “If you find one house spider, you have hundreds hidden.”

  Truth: Misleading. House spiders do not live in colonies or swarm. Each one keeps its own web and territory. Garages and sheds can hold many spiders in scattered corners, but most homes have only a handful at any time. One visible spider rarely means a hidden population.

• Myth 8

  Myth: “House spider egg sacs are dangerous and need professional removal.”

  Truth: False. Egg sacs are round, tan to pale brown, 6–9 mm across, and hold 100–400 eggs. They are harmless to touch. To remove one, knock it down with a broom or a vacuum nozzle. You need no chemical, and an intact sac releases nothing. The spiderlings inside cannot bite, even after they hatch.

Should you keep house spiders around?

For most homeowners, yes. Common house spiders are among the most useful small predators you can host indoors. They eat a good number of flies, mosquitoes, gnats, small moths, ants and small roaches. They are harmless to people and pets, and they need no care at all. Leaving them alone in garages, basements, attics and quiet ceiling corners is the simplest form of natural pest control there is.

There are fair exceptions. It is fine to remove a spider from a bedroom or main living space if one above your bed keeps you awake. People with severe arachnophobia gain nothing from living with webs in the living room. If the white droppings below a cobweb bother you, our guide to cleaning spider poop covers the stains, which are harmless. And if you have a guest who would not enjoy the biology lesson, a quick relocation is fine.

If you do remove a house spider, the cup-and-card method works well. Put a clear cup over the spider, slide a stiff card underneath, and carry it outside to a sheltered spot, such as an outdoor windowsill or under the eaves. Please do not crush it on the wall. You would be killing free pest control that was never going to harm you. For 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.

Steps that actually work

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.

Removing webs and egg sacs

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.

What you can realistically expect

Be realistic about the ceiling here. You will not clear house spiders out of any building that insects still walk into. The species is too widespread, too comfortable indoors, and far too good at laying eggs. A better goal is to keep living spaces clear and let a small population stay in the garage, the basement, and the outdoor-facing corners. That version holds, because those spiders eat the insects that would otherwise come further in.

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.