- Also called:
- widow spider
- On the Web:
- National Center for Biotechnology Information - Black Widow Spider Toxicity (Nov. 07, 2026)
black widow
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What is a black widow spider?
The black widow is a spider of the genus Latrodectus. It is known for the female's black color and a red hourglass-shaped marking on its abdomen. Black widows are found in the Americas, Australia, and New Zealand. They build tangle webs in woodpiles, burrows, and plants.
The black widow's venom contains a nerve toxin that can cause severe pain in humans, but bites are rarely fatal. The female spiders are much larger than the males and are known to sometimes kill and eat the males after mating, hence the name "black widow". They primarily prey on insects, using venom to subdue their prey and digestive enzymes to liquefy and consume them.
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Where do black widow spiders live?
Black widow spiders of the Latrodectus genus live in many areas worldwide. The southern black widow (L. mactans) is the most common in North America and is often found in brush piles and near dwellings, or on the ground in the southeastern United States. The western black widow (L. hesperus) inhabits western North America.
Other species reside in southern Europe, northern Africa, and southwestern Asia. The South American black widow (L. curacaviensis) lives under logs, debris, and trash. The redback (L. hasselti) lives in Australia and can be found in natural and urban areas in and near human dwellings. The KatipĆ (L. katipo) lives in New Zealand.
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How can you recognize a black widow spider?
The female southern black widow (Latrodectus mactans) is easily identified by its shiny black color and a reddish to yellow hourglass design on the underside of its spherical abdomen. However, sometimes two small triangles may be present instead of a complete hourglass. The body is about 1 cm (0.4 inch) long.
The male black widow is seldom seen and is about one-fourth to one-half the size of the female. In addition to the hourglass design, the male often has pairs of red and white stripes on the sides of its abdomen.
Black widows hang upside down in their web, making the hourglass mark conspicuous.
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What do black widow spiders eat?
Black widow spiders are predators that typically eat insects ensnared in their disorganized, mesh-like webs. To capture their prey, black widows use a comb-like structure on their hind legs to throw silk over their victims. After delivering an initial venomous bite, the spider punctures the insect's body and secretes digestive enzymes, allowing it to suck out the liquefied contents.
The black widow spider gets its name from the female's behavior of sometimes eating the male after mating, though this rarely happens in the wild. They are important predators of insects.
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Why are black widows known for their venom?
Black widow spiders are known for their potent venom, which contains a powerful nerve toxin. The venom causes severe pain in humans, especially in the abdominal region, and can lead to muscle stiffness, spasms, nausea, and mild paralysis, which makes breathing difficult. Though black widow bites are rarely fatal, they can be dangerous to small children and older people.
Female black widows have a distinct red hourglass-shaped marking on the underside of their abdomen, a warning coloration given the spider hangs upside down in its web, making the mark conspicuous. They use their venom to subdue prey, flinging silk over insects snared in their web using strong, curved bristles on their hind legs.
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What should you do if you are bitten by a black widow spider?
Black widow spiders are not aggressive, and bites to humans are rare. The bite may feel like a pinprick, and while most victims recover without complications, it can be fatal to very small children and older people. The bite often produces muscle stiffness and spasms, nausea, and mild paralysis of the diaphragm, which makes breathing difficult.
If bitten, seek medical attention, as clinics, poison control centers, and hospitals often have species-specific antivenin to treat the bite.
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black widow, (genus Latrodectus), any of about 30 species of comb-footed spiders distinguished by an hourglass-shaped marking on the abdomen and known for the venomous bite of the females. Black widows are found throughout much of the world and are so named for the femaleâs habit of eating the male after mating.
(Read Britannicaâs 6 Animals That Eat Their Mates)
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Arachnida
- Order: Araneae
- Infraorder: Araneomorphae
- Family: Theridiidae
See also list of arachnids
Natural history
The large web of black widows consists of a loosely organized mesh (cobweb). As comb-footed spiders, black widows have a row of strong, curved bristles on their hind pair of legs. This comb is used for adeptly flinging silk over prey snared in the web. Like most spiders, the black widow preys on insects. After its initial venomous bite, the spider makes small punctures in the victimâs body and secretes digestive enzymes; it then sucks out the contents as a liquid.
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The female may lay several masses of eggs during one summer. The egg case is suspended in the web and contains 250â750 eggs. It is white or tan in color, has a papery texture, and measures up to 1.25 cm (0.5 inch) in diameter. The young spiders, which are orange and white, emerge in 14 to 30 days. Females may live more than one and a half years.
As part of the food webs of the ecosystems they inhabit, black widows are attacked by mud dauber wasps (see thread-waisted wasp) and other insect parasites and predators.
Bite
Black widow spiders are not considered aggressive and bites to humans are rare. Females will bite to protect their eggs and young, and the potent venom contains a powerful nerve toxin; males are not known to bite humans. In humans, the bite often produces muscle stiffness and spasms, nausea, and mild paralysis of the diaphragm, which makes breathing difficult. Most victims recover without serious complications, but a bite can be fatal to very small children and older people.
(Read Britannicaâs list of 9 of the Worldâs Deadliest Spiders)
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Major species
The southern black widow (Latrodectus mactans) is the most common species of black widow in North America. The female is shiny black and usually has a reddish to yellow hourglass design on the underside of the spherical abdomen. Sometimes two small triangles, instead of a complete hourglass, are present. The body is about 1 cm (about 0.4 inch) long. The male, seldom seen, is between about one-fourth and one-half the size of the female. In addition to the hourglass design, the male often has pairs of red and white stripes on the sides of the abdomen.
In addition to L. mactans, four other black widow species are found in the United States: western black widow (L. hesperus), northern black widow (L. variolus), red widow (L. bishopi), and brown widow (L. geometricus), an invasive species. In the northern part of its range, L. mactans is found most often in brush piles and near dwellings. In the southeastern United States, however, it lives on the ground. L. hesperus is found in western North America.
Elsewhere, L. hystrix, L. dahli, and the white widow spider (L. pallidus) are found in southern Europe, northern Africa, and southwestern Asia, whereas the range of the European black widow, or karakurt (L. tredecimguttatus), extends from the western Mediterranean region to Central Asia.
The South American black widow (L. curacaviensis), whose geographic range encompasses the Lesser Antilles and South America, lives under logs, debris, and trash and frequents stone fireplaces. The brown widow (L. geometricus) is thought to have evolved in Africa, but the first specimen described came from South America. It is classified as an invasive species in many places outside its native range.
The redback (L. hasselti) lives in Australia and can be encountered in both natural and urban areas and in and near human dwellings. Although it is a significant venomous spider, its bites are rarely fatal. The KatipĆ (L. katipo) lives in New Zealand.