Venomous Spiders in the US: Black Widows, Recluses and More

Which US spiders are dangerous?

Nearly all of the more than 3,000 spider species in the US and Canada have venom, which they use to subdue insects. Almost none can harm people: most have fangs too small or weak to pierce human skin, or venom that causes no more than a brief sting. Having venom and being dangerous are two very different things.

Black widows

Three native black widows live in the US. All adult females are glossy black with a round abdomen, usually marked underneath with a red hourglass. Only adult females, with a body about 8–13 mm (0.3–0.5 in) long in the southern black widow, have fangs long enough to inject venom into people. Males are much smaller, often brown and striped, and harmless.

• Southern black widow (Latrodectus mactans): the Southeast, north to Ohio and west to Texas. Its hourglass is usually complete, and there is often a red spot above the spinnerets. See our southern black widow profile.
• Northern black widow (Latrodectus variolus): the Northeast, the Mid-Atlantic states and the Midwest, north into southern Canada. Its hourglass is often split into two separate marks.
• Western black widow (Latrodectus hesperus): the West, from Texas, Oklahoma and Kansas to the Pacific Coast and north into Canada.

Black widows build messy, three-dimensional cobwebs low to the ground: under stones and logs, in woodpiles, hollow stumps, rodent burrows, sheds, garages, crawl spaces and outdoor furniture. A female hangs upside down in her web, often at night, and usually drops or retreats if disturbed.

Their venom contains alpha-latrotoxin, a neurotoxin that can cause pain spreading from the bite, muscle cramps, sweating and nausea. These symptoms are very unpleasant but rarely life-threatening for healthy adults. For a closer look, read how dangerous is a black widow?

Brown and red widows

The brown widow (Latrodectus geometricus) is an introduced species, probably of African origin, now common around buildings in Florida and other Gulf states, Southern California and Hawaii. It is tan to dark brown with a black-and-white pattern on the back, an orange or yellowish hourglass underneath, and distinctive egg sacs covered in small spikes. Its bites are generally milder than a black widow’s. In Southern California researchers suspect it may be displacing the western black widow in some areas.

The red widow (Latrodectus bishopi) is found only in the sand pine scrub of central and southern Florida, where it webs in palmetto bushes. It has a red-orange head and legs and a black abdomen with red spots ringed in yellow, without a full hourglass. Because it lives in a habitat few people visit, bites on people are almost unknown.

Brown recluse

The brown recluse (Loxosceles reclusa) is a plain brown spider with a body about 6–13 mm (0.25–0.5 in) long and a darker violin-shaped mark on the front of its body, which gives it the nicknames fiddleback and violin spider. The violin is not a reliable identification mark, because many harmless spiders have similar markings. The best features are six eyes arranged in three pairs, uniformly colored legs without spines and a plain, unmarked abdomen.

Its native range lies south of a line from southeastern Nebraska through southern Iowa, Illinois and Indiana to southwestern Ohio, and from central Texas east to western Georgia. Reported bites come mostly from states such as Arkansas, Kansas, Missouri, Oklahoma and Texas. Single spiders hitchhike in boxes and furniture, but the species has not established populations far outside this range. Read where do brown recluse spiders live? for the full map.

Most brown recluse bites are minor and heal within about a week. A minority produce a sunken sore of dead skin that can take weeks or months to heal. Rarely, the venom affects the whole body, and very rare deaths have mostly involved young children. Our brown recluse profile covers its life history.

Other recluse spiders

The US has about a dozen recluse species. Besides the brown recluse, most are native to the deserts and dry hills of the Southwest, including the Texas recluse (Loxosceles devia), the Arizona recluse (L. arizonica), the Apache recluse (L. apachea) and the desert recluse (L. deserta) of California, Arizona and Nevada. They live under rocks, in rodent burrows and in packrat nests, far from most people, and bites are rarely reported.

Two recluses have been introduced. The Mediterranean recluse (L. rufescens) has been recorded in more than 20 states, usually as isolated populations inside individual buildings, and the Chilean recluse (L. laeta) has small populations in parts of Los Angeles County.

Feared but low-risk spiders

• Hobo spider (Eratigena agrestis): a brown funnel-web spider, 7–14 mm (0.3–0.55 in) long, introduced from Europe to the Pacific Northwest and Great Basin. It was blamed for skin wounds in the 1980s and 1990s, but later research found little evidence that its bite damages tissue, and the CDC no longer lists it as a venomous spider of concern.
• Yellow sac spiders (Cheiracanthium): small, pale yellow night hunters, 5–9 mm (0.2–0.35 in) long, that sometimes wander indoors. Their bites can cause local pain and swelling but not the tissue death once claimed.
• Wolf spiders: large, fast, hairy hunters such as the Carolina wolf spider, North America’s largest. They bite only if grabbed, and the bite is usually compared to a bee sting.
• Tarantulas: the big tarantulas of the South and Southwest can bite if handled, but the bite is generally mild; their irritating abdominal hairs are a bigger nuisance.
• False widows (Steatoda): dark, round-bodied cobweb spiders often mistaken for black widows, with much milder bites.

Why most “spider bites” are not spider bites

Spiders do not feed on people, and they bite only in defense, usually when trapped against the skin inside clothing, shoes, gloves or bedding. Yet doctors and patients often blame spiders for any red, painful or ulcerating skin lesion. Experts say a bite can only be confirmed when the spider is seen biting, collected and identified by a specialist.

The evidence is striking:

• A Kansas house: in 2001 researchers collected 2,055 brown recluses from one Kansas home over six months, yet the family of four living there had never been bitten.
• California’s missing recluses: in a nationwide study in which people mailed in spiders they believed were brown recluses, only one of 581 spiders sent from California was a brown recluse.
• Infections in disguise: methicillin-resistant Staphylococcus aureus (MRSA) and other bacterial infections cause sores that look like recluse bites. Nearly 30% of MRSA patients in one study first thought they had a spider bite.
• Unverified case reports: a 2016 review found that 78% of 134 published medical case reports of spider bites did not meet the criteria for a verified bite.

Avoiding bites

• Leave spiders alone. Do not handle widows, recluses or any large spider.
• Shake out clothing, shoes and gloves that have been stored in garages, sheds, attics or basements, and wear gloves when moving woodpiles, rocks or stored boxes.
• Look before you reach into dark corners, crawl spaces and outdoor furniture.
• If someone is bitten and develops severe pain, cramps or a spreading wound, or if a young child is bitten, seek emergency medical help immediately or call 911.

Many US spiders, from garden orb weavers to jumping spiders, are harmless and help control insects. For a regional look at both harmless and dangerous species, see spiders in Texas.