Summary
The southern black widow is the most familiar of the North American widow spiders, recognized by the glossy black female with a complete red hourglass on the underside of the abdomen. Bites are uncommon but medically significant; antivenom exists.
Quick answers
- Is Southern Black Widow dangerous to humans?
- Yes. Southern Black Widow is one of the few species in North America whose bite is established as medically significant. Adult-female bites can warrant medical evaluation.
- How big is an adult southern black widow?
- Adult female body length is 8–13 mm; males are 3–6 mm. Leg span reaches 25–38 mm.
- Where does Southern Black Widow live?
- Dim, sheltered outdoor sites: woodpiles, under stones, in sheds, garages, basements, outhouses, electrical boxes, and meter housings. Established U.S. populations occur in 23 states.
- What does Southern Black Widow eat and when is it active?
- Insects entangled in the cobweb - beetles, crickets, cockroaches, occasional small vertebrates. Nocturnal. Females are sedentary and rarely leave the web. Active year-round in southern range.
Identification
- Adult female: glossy jet-black, body 8–13 mm
- Complete red hourglass on underside of abdomen (the most reliable trait)
- Often a single red spot above the spinnerets
- Adult male: half the size of female, lighter brown with red and white markings - rarely seen
- Spherical, smooth abdomen
- Builds a tangled, messy web at ground level or near it
Morphometrics
| Measurement | Female | Male |
|---|---|---|
| Body length | 8–13 mm | 3–6 mm |
| Leg span | 25–38 mm | - |
| Lifespan | 1–3 years | - |
| Trait | Value |
|---|---|
| Web type | Three-dimensional irregular cobweb with strong, sticky gumfoot threads anchored to the substrate. |
| Eye arrangement | Eight eyes in two horizontal rows of four. |
| Eggs per sac | 100–400 |
| Egg sacs per year | 4–9 |
Geographic range
Native range: Southeastern United States, from southern New York to Florida, west through Texas and into the Midwest.
U.S. states with established populations: Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, West Virginia.
State pages covering Southern Black Widow
AlabamaArkansasDelawareFloridaGeorgiaIllinoisIndianaKansasKentuckyLouisianaMarylandMississippiMissouriNew JerseyNorth CarolinaOhioOklahomaPennsylvaniaSouth CarolinaTennesseeTexasVirginiaWest Virginia
Habitat & behavior
Habitat: Dim, sheltered outdoor sites: woodpiles, under stones, in sheds, garages, basements, outhouses, electrical boxes, and meter housings.
Activity: Nocturnal. Females are sedentary and rarely leave the web. Active year-round in southern range.
Diet: Insects entangled in the cobweb - beetles, crickets, cockroaches, occasional small vertebrates.
Venom & medical significance
| Venom property | Value |
|---|---|
| Type | Neurotoxic (alpha-latrotoxin) |
| LD₅₀ | 0.9 mg/kg (mouse) for purified alpha-latrotoxin |
| Note | Equine-derived antivenom (Antivenin Latrodectus mactans, Merck) available in the U.S. |
Bite symptoms & first aid
Symptoms
- Pinprick sensation at the bite, often with two tiny puncture marks
- Cramping pain spreading from the bite to the abdomen and back within 15–60 minutes
- Rigid, board-like abdominal muscles (latrodectism)
- Sweating, hypertension, nausea, restlessness
- Symptoms typically peak 12 hours after the bite and resolve in 1–3 days
Commonly confused with
- Brown widow
- False widow (Steatoda)
- Common house spider (juvenile)
Key facts
Sources
- [1]Black Widow Spiders - Clemson Cooperative Extension Home & Garden Information Center. Accessed 2026-06-14.
- [2]AAPCC National Poison Data System Annual Report - American Association of Poison Control Centers. Accessed 2026-06-14.
- [3]Black Widow Spider - University of Florida IFAS Entomology. Accessed 2026-06-14.