Western Black Widow
See a doctorLatrodectus hesperus · also called black widow
The western black widow is the widow of the western United States and the one most likely to turn up in a garage or under a barbecue. The red hourglass on the belly is genuinely diagnostic, and because the spider hangs upside down in its web, the underside is usually the part you can see.
If you think you were bitten
- Most suspected spider bites are not spider bites. Studies of patients presenting with a “spider bite” repeatedly find that the large majority are bacterial skin infections — frequently MRSA — which need antibiotics rather than reassurance. A spreading, painful, pus-filled sore is far more likely to be an infection than a spider.
- Wash it, ice it, and watch it. Clean the area with soap and water, apply a cold pack, and keep an eye on it.
- Get medical care if the wound spreads or darkens, if you develop cramping, sweating, fever or severe abdominal pain, or if you are confident it was a widow or a recluse.
- Bring the spider only if it is already dead and to hand. Do not go looking for it. Doctors treat symptoms, not species.
In the US, the Poison Help line is 1-800-222-1222. This site is a reference, not medical advice.
Quick facts
- Bite risk
- Venom is neurotoxic and can cause severe muscle cramping, sweating and abdominal pain — distressing and painful, and worth medical attention. Deaths are extremely rare in the modern era. Effects are systemic rather than local, so a widow bite does not produce a rotting wound.
- Size
- Body 8–16 mm. Female's body about the size of a large pea or small grape, with long thin glossy legs.
- Appearance
- Glossy jet-black globular abdomen with a red hourglass on the underside. Males are much smaller, brown, and marked with pale stripes — and are not a concern.
- Web
- A messy three-dimensional tangle of exceptionally strong silk, low down and in a sheltered spot — under garden furniture, in meter boxes, beneath stacked pots. The silk is noticeably tougher than other spiders' and crackles when broken.
- Found in
- garden, garage, woodpile, basement, desert
- Family
- Theridiidae
- Range
- 17 US states
How to identify a western black widow
- Complete red hourglass on the underside of the abdomen.
- Glossy, almost varnished black finish — widows look wet.
- Hangs upside down in a messy tangle web, low to the ground.
- Silk is unusually strong and audibly crackles when torn.
How it behaves
Shy and reluctant to bite. It stays in its web and drops or plays dead when disturbed. Bites usually happen when a spider is pressed against skin — reaching blind into a stored box, or putting on shoes left in a garage.
What the western black widow is confused with
One observation settles each of these.
False widows are dull brown rather than glossy black, and have a pale marbled pattern on the abdomen with no hourglass.
House spiders are dull tan-brown with a mottled abdomen and no hourglass, and build the same kind of tangle web.