Black Widow Identification: Hourglass, Web, Bite

Look at the underside of the abdomen for the hourglass. Penn State Extension describes the southern black widow female as shiny and jet black, 8 to 13 millimetres in body length and 25 to 35 millimetres with the legs extended, carrying an orange to red hourglass marking on the underside of the abdomen. The back may be unmarked or show up to four red dots. UC IPM gives the same picture for the adult female: shiny black body, slender black legs, and a red or orange hourglass underneath.

Males and juveniles look different enough to be missed. Penn State puts the male at 4 to 6 millimetres, black with white markings on the underbody and red spots. UC IPM describes immature and male widows as having white stripes on a tan abdomen. Penn State also notes that immature spiders cannot pierce human skin.

The web is a useful identification clue in its own right, because it is not a tidy orb. Penn State Extension describes widow webs as skimpy and disorganized, built under stones, in stumps or woodpiles, in vacant rodent holes and in the dark corners of barns and garages.

That list is a list of places where people put their hands without looking: reaching under a stack of firewood, feeling along the back of a shelf in an unlit garage, lifting a stone at the edge of a bed. Gloves and a flashlight solve most of the exposure.

UC IPM calls the black widow the most common harmful spider in California, so in the west this is the one to know rather than the brown recluse.

The bite itself is almost painless, according to Penn State Extension, with the pain arriving one to two hours later. Generalized symptoms including nausea, fever and muscle aches develop within one to three hours and generally dissipate within four days.

UC IPM adds that internal effects may range from mild to severe while there is often little to see at the bite site beyond local redness and swelling — which is exactly why a widow bite can be underestimated by someone looking at their skin. The venom acts on the nervous system rather than the tissue, so the wound stays unimpressive while the person feels increasingly unwell.

Severe cases warrant immediate medical attention. Penn State notes that treatment targets the symptoms with muscle relaxants and analgesics, and that antivenin exists but is generally reserved for extreme cases because of the risk of allergic reaction.

Penn State Extension gives two numbers worth holding onto: approximately 2,200 people are bitten in the United States by black widows every year, and no deaths have been recorded from black widow bites since 1983. The source describes deaths as extremely rare.

That is not a reason to ignore a bite. It is a reason to act on symptoms rather than on fear. UC IPM's first aid is to wash the bite and use ice, ice water or cold compresses, and to seek medical attention for an unusual or severe reaction such as increasing pain or extreme swelling. In the United States, Poison Help on 1-800-222-1222 reaches your local poison center free and confidentially, 24 hours a day.

Children, older adults and anyone with symptoms beyond the bite site should be seen promptly. Nothing here is a diagnosis.

Several common spiders are dark, round-bodied and found in the same corners. The features that do the work are the shine, the hourglass and the web.

• Check the underside. The hourglass is on the belly, not the back, so a photograph from above cannot settle it
• Check the size. Penn State's figures are 8 to 13 mm body and 25 to 35 mm with legs for the southern black widow female
• Check the legs. UC IPM describes slender black legs on the adult female, and white stripes on a tan abdomen on males and juveniles
• Check the web. Skimpy and disorganized, not a neat orb

Photograph the spider on a pale background from above and from below and the app identifies it. If you cannot reach the underside safely, do not try — a photo from a distance plus the web and location is still useful to an entomologist.

The spiders most often mistaken for black widows are the false widows in the genus Steatoda, which Wikipedia notes belong to the same family and are often mistaken for widows; their bite can be painful but is significantly less harmful. UC IPM gives the marks that separate them:

• False black widow (Steatoda grossa): chocolate brown and never has red on the belly.
• Noble false widow (Steatoda nobilis): mature females reach 5/8 inch (14 mm) in body length, larger than a western black widow's 1/2 inch.
• Brown widow (Latrodectus geometricus): a true widow, but a mottled mix of tan, brown and grey with a stripe on the back of the abdomen. Its egg sac is covered in silk spikes, like a very large pollen grain, while a black widow's egg sac is yellowish and teardrop-shaped, tapered at the top. UC IPM says brown widow bites cause burning pain at the site without the typical black widow symptoms.
• Northern black widow (Latrodectus variolus): a true black widow whose hourglass is broken into crosswise bars, with red spots on top of the abdomen (Orkin).

There are 35 widow species worldwide as of October 2025 (Wikipedia), and several live in the United States:

• Southern black widow: the American South (Orkin).
• Northern black widow: the Northeast, extending into Canada and south to Florida and Texas; Orkin says it is rarely found indoors.
• Western black widow: western Canada, the United States and Mexico (Wikipedia); UC IPM describes the female as shiny jet black with a red hourglass, about 1/2 inch.
• Brown widow: widely distributed (Wikipedia); Orkin places it in the South.
• Red widow: also listed for the United States (Wikipedia).

None of the sources used here rank states by how many black widows they have. What they do show is that there is a widow species across most of the country, so the species name matters more than the state.

Black widows are nocturnal and come out at dusk (UC IPM), so the time you are most likely to see one on its web is at night with a flashlight, and the time you are most likely to be bitten is when reaching into a dark space during the day. By season, NW Exterminating, a pest control company in southern Arizona, reports peak activity from April through October and the least activity from January through March; in colder regions the season is likely shorter.

Black widow bites are not rare, but deaths are. Wikipedia reports that about 2,500 people in the United States report being bitten by a black widow each year and that most do not need medical treatment, and that a 2012 review by the American Association of Poison Control Centers found no deaths from black widows since 1983. Penn State Extension's figure, above, is about 2,200 bites a year. Black widows are not especially aggressive and rarely bite unless startled or threatened (Wikipedia).

The venom is potent all the same: it contains the neurotoxin latrotoxin (Wikipedia). UC IPM lists rigid stomach muscles, sweating and pain that may be local, radiating or regional among the symptoms, and says antivenom is available. If you think a black widow has bitten you, call Poison Help at 1-800-222-1222 in the United States or get medical care, especially for muscle cramps, stomach rigidity, sweating or any bite in a child.

Research and drafting for this page used AI assistance. Every figure, date and quotation was then checked line by line against the sources listed at the bottom of the page, each of which was opened while writing. Nothing here is a diagnosis. If a bite, sting or contact with an insect is followed by trouble breathing, swelling of the face or throat, spreading redness, fever or any symptom that worries you, get medical care; in the United States Poison Help (1-800-222-1222) is free and open 24 hours a day.