Check the underside. A female black widow is glossy black with a red or orange hourglass on the underside of her round abdomen. False widows (spiders in the genus Steatoda) have the same round-bodied shape but are usually brown to purplish-black, often with pale markings on top, and they never have a bright red hourglass. False widow bites are usually minor; black widow bites can cause serious symptoms and need medical advice.
Side-by-side comparison #
| Feature | Black widow (female) | False black widow | Noble false widow |
|---|---|---|---|
| Scientific name | Latrodectus species | Steatoda grossa | Steatoda nobilis |
| Color | Shiny, jet black | Purplish brown to black, satin rather than glossy | Brown with cream markings on the abdomen |
| Hourglass | Red or orange, on the underside | None | None |
| Markings on top | Usually none (some species have red spots) | Faint pale markings | Pale pattern often likened to a skull |
| Legs | Long, slender, black | Brown to dark | Reddish-orange |
| Body length | Around 1/2 inch for adult females | About 6 to 10.5 mm (females) | About 9.5 to 14 mm (females) |
| Where | Most of the US, in dark, dry, undisturbed spots | Worldwide in houses, sheds, window frames | Western Europe, UK, Ireland, parts of coastal California |
| Bite | Can cause significant pain, cramping and illness | Usually minor | Usually like a bee sting; occasionally worse |
How to recognize a black widow #
UC IPM describes the mature female black widow as having a shiny black body, slender black legs, and a red or orange hourglass mark on the underside of her large, round abdomen. Black widows build messy, tangled cobwebs in dark, dry, sheltered and undisturbed places: woodpiles, garages, sheds, meter boxes, under outdoor furniture and in the corners of crawlspaces.
A few things surprise people:
- The hourglass is underneath. Black widows usually hang upside down in their webs, so the mark is visible from below. From above, you may only see a shiny black ball.
- Not every widow is solid black with a perfect hourglass. The northern black widow’s hourglass is often split into two separate marks, and some widows have red spots on top as well.
- Males and young widows look different. UC IPM notes that males and immature females have white stripes on a tan abdomen. They’re much less of a concern than mature females.
- Brown widows exist too. In the southern US and California, the brown widow is tan to brown with an orange hourglass underneath and makes egg sacs covered in pointed bumps.
How to recognize a false widow #
“False widow” covers several Steatoda spiders, which belong to the same cobweb-spider family as widows and share their round, shiny look.
False black widow (cupboard spider) #
The false black widow, Steatoda grossa, is common in homes and sheds in North America and many other regions. It’s native to Europe and temperate Asia. Females are about 6 to 10.5 mm long with a round, bulbous abdomen colored purplish-brown to black, often with faint lighter markings. It has no red hourglass and no bright markings of any kind, which is the key difference.
Bites are uncommon and usually minor, causing local pain and sometimes blistering. Rare cases involve fever or nausea lasting a few days.
Noble false widow #
The noble false widow, Steatoda nobilis, is the “false widow” in UK and Irish news stories. It’s brown with cream markings on the abdomen that people often compare to a skull, and reddish-orange legs. Females are about 9.5 to 14 mm long. Originally from Madeira and the Canary Islands, it has spread through England, Ireland and parts of Europe, and has been found in coastal California since at least 2011.
Most bites feel like a bee or wasp sting. A minority cause more intense pain around the bite, and rare cases involve infection of the wound. That’s a reason to keep any spider bite clean and to get it checked if redness spreads.
Other black spiders that get mistaken for widows #
- Common house spider: a small, brownish cobweb spider with a mottled round abdomen, found in corners and windows. Harmless.
- Bold jumping spider: black and fuzzy with white spots or stripes and iridescent green mouthparts. It hunts in daylight and hops, instead of sitting in a web. Harmless to people.
- Black ground spiders: fast-running, flat spiders with no web and no hourglass.
What to do about a black widow #
Don’t handle it. Use a long tool to knock down the web and sweep the spider into a jar, or simply avoid the area and wear gloves when working in garages, woodpiles and sheds in black widow country. Clearing clutter and debris around the house removes the undisturbed spots they need.
If someone is bitten, UC IPM’s advice is to stay calm and promptly seek medical advice. Symptoms are mostly internal: there may be little more than redness and swelling at the bite, but pain can spread and muscles can cramp, especially in the abdomen. In the US:
- Call Poison Control at 1-800-222-1222, free and confidential, for guidance.
- Call 911 for trouble breathing, severe pain, chest pain, or signs of an allergic reaction.
- Wash the bite with soap and water and apply a cold pack while you get advice.
- If it’s safe, bring the spider in a sealed jar for identification.
Young children, older adults and people with heart or blood pressure problems are more vulnerable, so don’t wait and see with them.
Checking a spider from a photo #
Photographing the underside is the best way to confirm a widow without getting close. Shine a flashlight on the web and photograph the spider from below, where the hourglass is. A top view helps too, to show the pattern. Our guide to identifying a spider by photo has more tips.
Insect Identity knows the black widow, false black widow, common house spider and bold jumping spider, so it can separate the common look-alikes in about a second, offline, with a confidence score and four runners-up. It doesn’t include the noble false widow or the brown widow, so those may come back as a close relative with a lower score. And it’s an identification aid, not a medical tool: for any bite, follow Poison Control and medical advice whatever the app says. For other spider mix-ups, see brown recluse vs wolf spider and spider or tick.
Frequently asked questions #
Are false widow spiders dangerous? #
Generally not. Most false widow bites cause pain and redness similar to a bee sting that fades within a day or two. Occasionally a bite causes stronger pain or becomes infected, so clean it and see a doctor if it’s getting worse rather than better.
Do false widows have a red hourglass? #
No. A red or orange hourglass on the underside is the signature of true widows (Latrodectus). False widows may have pale or cream markings on top, but no red hourglass.
Can a black widow have no hourglass? #
Mature female black widows nearly always have a red or orange marking underneath, though in some species it’s broken into two parts or looks more like spots. Males and juveniles have different, paler patterns and can be hard to recognize.
Where do black widows usually hide? #
Dark, dry, undisturbed places: woodpiles, sheds, garages, crawlspaces, under patio furniture, inside meter boxes and around outdoor clutter. They’re rarely found in the open parts of a living space.