Southern black widow vs Western black widow
These two are easy to mix up. Here's how to tell a southern black widow from a western black widow, and whether either one bites or stings.
Southern black widow
Latrodectus mactans
Western black widow
Latrodectus hesperus
≠The key differences
Very similar in appearance; geographic ranges overlap in parts of the US—identification often requires range and subtle pattern differences or expert examination.
⚖︎Side by side
| Southern black widow | Western black widow | |
|---|---|---|
| To humans | Venomous bite | Venomous bite |
| Size | Females 8-13 mm body length; males 3-6 mm body length | Females 7-13 mm body length; males 3-6 mm body length |
| Colours | Black, Red, Brown, White | Black, Red (hourglass), Brown (male/patterns) |
| Family | Theridiidae | Theridiidae |
| Habitat | Sheltered, undisturbed sites near the ground: woodpiles, boxes, garages, basements, crawlspaces, hollow stumps, under eaves and inside cluttered storage. | Dry, sheltered sites near the ground or in human structures: woodpiles, sheds, crawl spaces, garages, rock crevices, under ledges and in dense vegetation. |
| Range | Southeastern and south-central United States, west to Texas and Oklahoma and north to about the Ohio Valley and southern New England; most common in the southeast. Exact range and taxonomy can vary with local populations. | Western North America: western United States, southwestern Canada and parts of northern Mexico |
| Active | Most active in warm months (spring to fall); nocturnal and most active at night when hunting in their webs. | Spring through fall; most active at night |
| Pest? | No | Yes |
🔍How to spot a southern black widow
- Shiny black, globular abdomen on females with a red hourglass marking on the ventral side.
- Females 8-13 mm body length; males much smaller and often brownish with dorsal markings.
- Tangled irregular cobwebs in sheltered, undisturbed areas near the ground or in buildings.
- Hourglass marking is usually on the underside of the abdomen; look at web location and body shape if marking is not visible.
🔍How to spot a western black widow
- Shiny black, globose abdomen on females with a red or red-orange hourglass marking on the underside
- Females larger (7-13 mm) and more robust than males (3-6 mm); males are often brownish with dorsal patterns
- Irregular, tangled cobwebs in sheltered, low locations (near the ground, under eaves, inside sheds)
- Smooth, glossy abdomen (not notably hairy) and relatively long, slender legs
?Frequently asked questions
What is the difference between a southern black widow and a western black widow?
Very similar in appearance; geographic ranges overlap in parts of the US—identification often requires range and subtle pattern differences or expert examination.
Is a southern black widow or a western black widow more dangerous?
Southern black widow: Venomous bite. Western black widow: Venomous bite. Female bites inject neurotoxic venom (latrotoxin) that can cause local pain, muscle cramps, sweating, nausea, elevated blood pressure, and in severe cases respiratory difficulty. Females are venomous; bites can cause latrodectism (local pain, muscle cramps, sweating, nausea, elevated blood pressure).
Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.