Medically significant. A bite can cause severe muscle pain and cramping that can require medical care. Deaths are very rare. The spider is not aggressive and bites when pressed against skin.
We identify, we don't diagnose. If you've been bitten or stung and symptoms develop, or you're worried, seek medical attention.
Size8–13 mm body for the female; males are much smaller and harmless
MarkingsGlossy jet-black, round bulbous abdomen · Red hourglass on the underside — you must see the belly
WhereWoodpiles, meter boxes, under garden furniture, sheds and crawl spaces.
SeasonMost often noticed late summer into autumn
What it is not
A black widow is most often confused with a species that is medically significant. If you are trying to rule those out, check these:
Red hourglass on the underside — you must see the belly
Slender unbanded legs, first pair longest
Tangled, strong, irregular web low to the ground
Hangs upside-down in the web
Where you’ll find it
The southern black widow occupies the southeastern and south-central United States. Related widows cover most of the rest of the country, so somewhere in the US almost everyone has a widow species locally.
Woodpiles, meter boxes, under garden furniture, sheds and crawl spaces.
Most often noticed late summer into autumn.
How it behaves
It is nocturnal, stays in its web, and hangs upside-down, which is why the hourglass on the underside is the marking people are told to look for. It is not aggressive and its first response to disturbance is to drop and play dead or retreat. Nearly all bites happen when the spider is pressed against skin — a hand into a woodpile, a foot into a boot, or reaching blindly under garden furniture. The web is strong and untidy, and it crackles audibly when broken.
What a bite looks like
Often unremarkable at the site: a small red mark, sometimes with two faint punctures and a pale ring. The bite site is not the point with a widow — the systemic effects are.
A sharp pinprick, then severe muscle pain and cramping that spreads from the bite over the following hours, often to the abdomen or back. Sweating, nausea and a raised heart rate are common.
We identify, we don't diagnose. In the US, call Poison Control at 1-800-222-1222 after a suspected widow bite. Call emergency services for difficulty breathing, collapse, seizure or severe weakness.
A skin mark cannot confirm which animal caused it. Read the bug bite and sting guide for the limits and the symptoms that should end an online search.
You’ve found one indoors
Do not reach into places you cannot see. Wear gloves in woodpiles, meter boxes and under garden furniture, and knock out boots and gloves that have been stored outdoors. If you find one indoors, a vacuum removes spider, web and egg sacs together without anyone getting close.
Common questions
How dangerous is a black widow bite?
It is medically significant and warrants expert advice, but it is very rarely fatal. Modern deaths are extremely rare, and effective antivenom exists. Severe reactions are most likely in children and older adults.
Do male black widows bite?
Effectively no. Males are much smaller, differently marked, and are not considered a risk to people. When someone is bitten it is by an adult female.
What if I cannot see the hourglass?
Then do not rule a widow out. The mark is on the underside, and on some individuals it is split, faint, or orange rather than red. A glossy black spider with a round abdomen in a tangled ground-level web is worth treating as a widow until you can see otherwise.
Where are black widows usually found?
Low down, in sheltered dark gaps: woodpiles, meter boxes, under garden furniture, in sheds and crawl spaces, and among stored pots. They are outdoor spiders that occasionally come inside.
Haydeé Salmones · CC-BY-SA