Summary
The northern black widow is the widow species of the northeastern United States and southeastern Canada. The female is distinguished from L. mactans by a broken (not continuous) red hourglass and a row of red spots running down the dorsal midline of the abdomen.
Quick answers
- Is Northern Black Widow dangerous to humans?
- Yes. Northern 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 northern black widow?
- Adult female body length is 9–11 mm; males are 4–5 mm. Leg span reaches 25–38 mm.
- Where does Northern Black Widow live?
- Forested areas more than urban environments. Found in tree stumps, hollow logs, abandoned rodent burrows, and outbuildings. Established U.S. populations occur in 18 states.
- What does Northern Black Widow eat and when is it active?
- Insects entangled in the cobweb. Nocturnal; sedentary on the web. Active April–October in the north.
Identification
- Glossy black female, body 9–11 mm
- Broken (two-piece) red hourglass on underside - not connected at the waist
- Row of red spots down the dorsal midline of the abdomen
- Diagonal white or yellow lateral stripes on sides of abdomen
- Prefers wooded habitat over urban structures
Morphometrics
| Measurement | Female | Male |
|---|---|---|
| Body length | 9–11 mm | 4–5 mm |
| Leg span | 25–38 mm | - |
| Lifespan | 1–3 years | - |
| Trait | Value |
|---|---|
| Web type | Tangled three-dimensional cobweb with gumfoot threads at ground level. |
| Eye arrangement | Eight eyes in two horizontal rows of four. |
| Eggs per sac | 100–400 |
| Egg sacs per year | 3–6 |
Geographic range
Native range: Eastern North America from southern Canada through New England and the Appalachian region south to northern Florida.
U.S. states with established populations: Connecticut, Florida, Georgia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Vermont, Virginia, West Virginia.
State pages covering Northern Black Widow
ConnecticutFloridaGeorgiaMaineMarylandMassachusettsNew HampshireNew JerseyNew YorkNorth CarolinaOhioPennsylvaniaRhode IslandSouth CarolinaTennesseeVermontVirginiaWest Virginia
Habitat & behavior
Habitat: Forested areas more than urban environments. Found in tree stumps, hollow logs, abandoned rodent burrows, and outbuildings.
Activity: Nocturnal; sedentary on the web. Active April–October in the north.
Diet: Insects entangled in the cobweb.
Venom & medical significance
| Venom property | Value |
|---|---|
| Type | Neurotoxic (alpha-latrotoxin) |
| LD₅₀ | 0.9 mg/kg (mouse) |
| Note | Clinically indistinguishable from L. mactans; same antivenom is effective. |
Bite symptoms & first aid
Symptoms
- Latrodectism: cramping pain, sweating, abdominal rigidity
- Symptoms peak within 12 hours, resolve in 1–3 days with care
Commonly confused with
- Southern black widow
- Brown widow
- False widow
Key facts
- The broken (two-piece) red hourglass is the single most reliable trait separating L. variolus from L. mactans in the field. [1]
Sources
- [1]Northern Black Widow Spider - Penn State Extension. Accessed 2026-06-14.
- [2]Latrodectus variolus species page - BugGuide.net (Iowa State University). Accessed 2026-06-14.