Southern black widow vs Common house spider
These two are easy to mix up. Here's how to tell a southern black widow from a common house spider, and whether either one bites or stings.
Southern black widow
Latrodectus mactans
Common house spider
Parasteatoda tepidariorum
≠The key differences
Latrodectus species have a glossy black body often with a red hourglass marking on the underside of the abdomen and carry medically significant venom; Parasteatoda is usually brown/tan and lacks the distinctive hourglass.
⚖︎Side by side
| Southern black widow | Common house spider | |
|---|---|---|
| To humans | Venomous bite | Mild bite |
| Size | Females 8-13 mm body length; males 3-6 mm body length | Females 5-8 mm body length; males 3-6 mm body length |
| Colours | Black, Red, Brown, White | Brown, Tan, Cream, Dark brown |
| Family | Theridiidae | Theridiidae |
| Habitat | Sheltered, undisturbed sites near the ground: woodpiles, boxes, garages, basements, crawlspaces, hollow stumps, under eaves and inside cluttered storage. | Sheltered indoor and peridomestic sites: corners, ceilings, basements, attics, garages, window frames, behind furniture and under eaves. |
| 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. | Probably native to South America but now cosmopolitan; found across North America, Europe, Asia, and other temperate regions often associated with human structures. |
| Active | Most active in warm months (spring to fall); nocturnal and most active at night when hunting in their webs. | Year-round indoors; most active at night when hunting and maintaining webs. |
| 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 common house spider
- Irregular, three-dimensional tangled web in sheltered indoor corners with a silken retreat.
- Rounded, somewhat bulbous abdomen with variable brown/tan markings.
- Females noticeably larger and more robust than males; males slimmer with visible pedipalps.
- Shorter legs relative to long-legged house spiders; abdomen often patterned rather than uniformly black.
?Frequently asked questions
What is the difference between a southern black widow and a common house spider?
Latrodectus species have a glossy black body often with a red hourglass marking on the underside of the abdomen and carry medically significant venom; Parasteatoda is usually brown/tan and lacks the distinctive hourglass.
Is a southern black widow or a common house spider more dangerous?
Southern black widow: Venomous bite. Common house spider: Mild 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 are rare and usually occur only if the spider is trapped against skin.
Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.