Most spiders you’ll find inside a Missouri home are harmless. The usual residents include common house spiders, cellar spiders, and the occasional wolf spider or crab spider that wandered in from outside. Missouri is also home to two medically significant species, the brown recluse and the black widow, both of which can show up indoors. Knowing which is which saves you from unnecessary panic and helps you spot the ones that actually matter.
Common House Spiders
The species you’ll encounter most often is the common house spider (sometimes called the American house spider). It has a grey body with white marbling and banded legs, and its rounded, bulbous abdomen gives it a body shape that looks alarmingly similar to a black widow at first glance. The coloring is the giveaway: grey and mottled rather than glossy black. These spiders build messy, irregular webs in corners, window frames, and behind furniture. They feed on flies, crickets, and other household pests, and they pose no danger to people.
Cellar Spiders
If you’ve seen a tiny, pale spider with impossibly long, thin legs hanging upside down from the ceiling, that’s a cellar spider. Their bodies are only about a quarter inch long, grey or tan, sometimes with a peanut-shaped abdomen and darkened “knobby” joints on the legs. They build loose, messy cobwebs in corners and crevices, particularly in basements, garages, and crawl spaces.
Cellar spiders are more interesting than they look. Their webs aren’t sticky. Instead, they rely on the tangled matrix of silk to snag prey, which they quickly bite and wrap. They routinely take down prey much larger than themselves, including wolf spiders and crane flies. Some cellar spiders will even invade another spider’s web, jiggle the silk to mimic a trapped insect, then attack the host spider when it comes to investigate. In parts of the world where dangerous spiders are common indoors, cellar spiders are considered welcome houseguests for exactly this reason.
Brown Recluse Spiders
Missouri sits squarely in brown recluse territory. The Missouri Department of Conservation lists them as “common and sometimes abundant” statewide. Originally concentrated in southern counties, they’ve gradually spread northward and now occur in homes across the entire state.
A brown recluse is a small spider, about three-eighths of an inch in body length, roughly the size of a quarter including its legs. It’s a uniform grayish yellow-brown with long, slim legs. The famous violin-shaped marking sits on the front section of the body, with the “neck” of the violin pointing toward the abdomen. But the most reliable identification feature is the eyes: brown recluses have six eyes arranged in three pairs, while almost all other spiders have eight. You’ll need a magnifying glass to see this clearly, but it’s the one feature that rules out every lookalike.
How to Rule Out a Brown Recluse
Many brown spiders get mistaken for brown recluses. A few quick checks eliminate most of them. If the spider has more than one color on its legs (stripes or bands), it’s not a recluse. If the abdomen has two or more pigment colors, it’s not a recluse. If the legs have thick, conspicuous spines rather than fine hairs, it’s not a recluse. And if the body is longer than half an inch, it’s too big to be one. Cellar spiders, funnel weavers, wolf spiders, and orbweavers all get confused for recluses regularly, but each fails at least one of these checks.
Where They Hide Indoors
Brown recluses prefer undisturbed, dark spaces. They commonly hide in little-used drawers, closets, attics, basement areas, and behind baseboards and furniture. They can’t climb smooth surfaces, which is why they’re often found trapped in bathtubs and sinks. Their habit of tucking into packed-away clothing and towels is what leads to most bites: someone reaches into a box of stored linens or pulls on shoes that have been sitting in the closet for weeks, and the spider, pressed against skin, bites defensively.
July and August are peak brown recluse season in Missouri. When temperatures stay above 80°F even at night, recluses become more active, hunting insects, seeking mates, and dispersing. Inside homes, air conditioning creates a temperature difference between living spaces and undisturbed zones like wall voids, attics, and storage rooms. Recluses move between these zones, and that movement is what brings them into contact with people.
What a Brown Recluse Bite Looks Like
Most bites go unnoticed at first. Within three to eight hours, the area becomes red, sensitive, and feels like it’s burning. The bite site may develop a bullseye pattern or bruise with a bluish tint. If only a small amount of venom was injected, the discomfort resolves within a few days. In more severe cases, an ulcer forms at the bite site within three to five days, and by one to two weeks, the surrounding skin can break down into a wound that takes months to fully heal. A thick black scab typically covers the wound around the three-week mark.
If you’re bitten, clean the area immediately with soap and water, apply a cold damp cloth to reduce swelling, and elevate the area if possible. Severe symptoms, spreading redness, or an expanding wound warrant medical attention promptly.
Black Widow Spiders
Missouri has two black widow species: the southern black widow, more common in the southern half of the state, and the northern black widow, found statewide. Black widows are less likely to turn up inside your living space than brown recluses. They prefer outdoor or semi-outdoor spots: under rocks and logs, along foundations, in garages, sheds, and crawl spaces.
The female southern black widow is the classic image: a glossy black body with a red hourglass on the underside of the abdomen, both halves of the hourglass connected. The northern black widow’s hourglass is broken into two separate red spots, and she often has a row of red dots along the top of the abdomen with diagonal whitish markings on the sides. Males of both species are smaller and typically have faint red or white spots on top of the abdomen. Black widow webs are distinctively strong and sticky, with an irregular, tangled structure and a small funnel where the spider retreats when disturbed.
Keeping Spiders Out of Your Home
Regular, thorough cleaning is the single most effective spider deterrent. A vacuum cleaner removes spiders, webs, and egg sacs in one pass. Focus on corners, crevices, and undisturbed dark areas, using a bright flashlight to find what you’d otherwise miss. Reducing clutter in basements, attics, and closets eliminates the sheltered hiding spots spiders need.
Outside the house, move firewood, stacked materials, and debris away from the foundation. Trim back any shrubs, vines, or tree limbs that touch the house, since these give spiders a direct bridge to the structure. Install tight-fitting window screens and door sweeps to close off entry points. At exterior doors, switching to yellow or sodium vapor light bulbs helps too. These attract fewer night-flying insects, which means fewer spiders following the food source to your doorstep.
For homes with persistent problems, especially in brown recluse territory, a barrier insecticide spray applied around the building’s perimeter can reduce spider entry. Pay particular attention to door thresholds, garage entrances, crawl space openings, foundation vents, and the bottom edge of siding. These treatments typically need reapplication monthly or every other month during warmer weather, roughly May through September in Missouri.