Southern black widow vs Northern black widow
These two are easy to mix up. Here's how to tell a southern black widow from a northern black widow, and whether either one bites or stings.
Southern black widow
Latrodectus mactans
Northern black widow
Latrodectus variolus
≠The key differences
Its red hourglass is usually split into two separate marks, and it often has a row of red spots on the back; L. variolus tends to occur further north and may show variable dorsal markings. Identification often requires geographic context or expert examination.
L. mactans is more common in the southeastern United States, and ranges overlap; L. mactans usually has a complete, joined hourglass and lacks the row of red spots on top of the abdomen that L. variolus usually shows.
⚖︎Side by side
| Southern black widow | Northern black widow | |
|---|---|---|
| To humans | Venomous bite | Venomous bite |
| Size | Females 8-13 mm body length; males 3-6 mm body length | Females about 8-13 mm body length; males about 3-6 mm |
| Colours | Black, Red, Brown, White | Glossy black, Red (hourglass marking), Brown (male) |
| Family | Theridiidae | Theridiidae |
| Habitat | Sheltered, undisturbed sites near the ground: woodpiles, boxes, garages, basements, crawlspaces, hollow stumps, under eaves and inside cluttered storage. | Undisturbed, sheltered locations near the ground: woodpiles, garages, basements, sheds, crawl spaces, hollow logs and under stones or debris. |
| 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. | Eastern North America: southeastern Canada (southern Ontario to the Maritimes) and the eastern United States south to northern Florida and west to the Great Plains, most common in the Northeast. |
| Active | Most active in warm months (spring to fall); nocturnal and most active at night when hunting in their webs. | Most active spring through early fall; nocturnal and crepuscular (active at night and twilight). |
| Pest? | No | No |
🔍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 northern black widow
- Glossy, rounded black abdomen on females with a red hourglass on the underside that is usually split into two parts.
- Females larger and more bulbous than males; males are smaller, slimmer and more patterned.
- Irregular, tangled cobwebs in sheltered, low locations like woodpiles, sheds, and basements.
- A row of red spots on the top of the abdomen and a broken hourglass point to the northern black widow; a complete hourglass and no dorsal spots suggest the southern black widow.
?Frequently asked questions
What is the difference between a southern black widow and a northern black widow?
Its red hourglass is usually split into two separate marks, and it often has a row of red spots on the back; L. variolus tends to occur further north and may show variable dorsal markings. Identification often requires geographic context or expert examination. L. mactans is more common in the southeastern United States, and ranges overlap; L. mactans usually has a complete, joined hourglass and lacks the row of red spots on top of the abdomen that L. variolus usually shows.
Is a southern black widow or a northern black widow more dangerous?
Southern black widow: Venomous bite. Northern 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. Bites inject neurotoxic venom that can cause latrodectism: pain spreading from the bite, sweating, nausea, muscle cramps and abdominal rigidity, sometimes with raised 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.