Spider Pest Authority
Identification, venom, and range data
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Theridiidae · Cobweb spiders

Brown Widow

Latrodectus geometricus

Moderate· Body ♀ 7–12 mm· 12 state range· Last reviewed June 2026
Juvenile brown widow (Latrodectus geometricus).
Juvenile brown widow (Latrodectus geometricus). · Wikimedia Commons

Summary

An invasive widow that has rapidly displaced native black widows across the southern United States. The brown widow's venom is comparable in potency to the black widow's, but smaller venom yields produce milder envenomations.

Quick answers

Is Brown Widow dangerous to humans?
Sometimes. Brown Widow bites are usually self-limiting, but a minority of cases produce notable local symptoms. Most do not require medical care.
How big is an adult brown widow?
Adult female body length is 7–12 mm; males are 3–5 mm. Leg span reaches 20–35 mm.
Where does Brown Widow live?
Built environments: under patio furniture, mailboxes, eaves, playground equipment, and stored items. Strongly anthropophilic. Established U.S. populations occur in 12 states.
What does Brown Widow eat and when is it active?
Small insects. Nocturnal; sedentary on the web.

Identification

  • Tan to dark brown body with variable mottled markings
  • Orange to yellow hourglass on underside (color is the key trait, not black)
  • Geometric pattern on dorsal abdomen - bands of cream, brown, and black
  • Distinctive spiky/tufted egg sac (looks like a small mace)
  • Body 7–12 mm; smaller and more slender than black widow

Morphometrics

MeasurementFemaleMale
Body length7–12 mm3–5 mm
Leg span20–35 mm -
Lifespan1–2 years -
TraitValue
Web typeTangled cobweb with gumfoot threads, distinctive spiky egg sac.
Eye arrangementEight eyes in two rows of four.
Eggs per sac120–150
Egg sacs per year10–20

Geographic range

Native range: Probably southern Africa; introduced and now established across the U.S. South, Caribbean, and globally in tropical and subtropical regions.

U.S. states with established populations: Alabama, Arizona, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, Nevada, North Carolina, South Carolina, Texas.

State pages covering Brown Widow

AlabamaArizonaCaliforniaFloridaGeorgiaHawaiiLouisianaMississippiNevadaNorth CarolinaSouth CarolinaTexas

Habitat & behavior

Habitat: Built environments: under patio furniture, mailboxes, eaves, playground equipment, and stored items. Strongly anthropophilic.

Activity: Nocturnal; sedentary on the web.

Diet: Small insects.

Venom & medical significance

Venom propertyValue
TypeNeurotoxic (alpha-latrotoxin)
LD₅₀Comparable to L. mactans on per-mg basis
NoteSmaller venom yield and more reclusive behavior result in clinically milder bites than black widow.

Bite symptoms & first aid

Symptoms

  • Localized pain at the bite site
  • Latrodectism symptoms when present are typically milder than black widow
  • Most reported bites resolve without antivenom

Commonly confused with

  • Black widow
  • False widow
  • Common house spider

Key facts

  • Spiky egg sacs are diagnostic - no other North American widow produces them. [1]
  • Brown widows have been documented displacing native black widows in southern California urban environments since the early 2000s. [2]

Sources

  1. [1]Brown Widow Spider - University of Florida IFAS Entomology. Accessed 2026-06-14.
  2. [2]Vetter et al., Geographic expansion of the brown widow spider - Journal of Medical Entomology. Accessed 2026-06-14.