Western counterpart to the southern black widow. Same medical concerns; bites painful but rarely fatal with modern care.

Also called: Western Widow

Native status: Native to western US and Canada

§ Quick facts

SizeFemales 8–13 mm body; males 3–6 mm
WeightFemales ~1 g
LifespanWild 1–3 years
OrderAraneae
FamilyTheridiidae

§ Encyclopedia

Latrodectus hesperus, the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm in length and is black, often with an hourglass-shaped red mark on the lower abdomen. This "hourglass" mark can be red, yellow, and on rare occasions, white. The male of the species is around half this length, and generally a beige color with lighter striping on the abdomen. The population was previously described as a subspecies of Latrodectus mactans, and it is closely related to the northern species Latrodectus variolus. The species, as with others of the genus, build irregular or "messy" webs. Unlike the spiral webs or the tunnel-shaped webs of some other spiders, the strands of a Latrodectus' web have no obvious overall organization.

Source: Wikipedia — Latrodectus hesperus Licensed under CC BY-SA 4.0

§ Identification

Field marks. Females: glossy jet-black with iconic red hourglass on underside of abdomen. Males: brown with reddish markings, much smaller, no hourglass.

Similar species. Southern Black Widow (eastern range; very similar). Brown Widow (lighter color, geometric pattern). Northern Black Widow (broken hourglass).

Voice. N/A

§ Diet & behavior

Diet. Insects caught in tangled cobweb: flies, beetles, mosquitoes, occasionally larger prey like crickets and small lizards.

Behavior. Western counterpart to the Southern Black Widow. Bites only defensively when pressed against skin; venom is neurotoxic and bites can cause severe pain, muscle cramps, sweating, and (rarely) more serious complications. Antivenom available. Builds irregular tangle webs (cobwebs) in sheltered locations: woodpiles, sheds, outhouses, foundation crevices, mailboxes. Hangs upside-down at center of web.

§ Range

Western US, Canada

§ Habitat

Sheltered dark corners

§ Threats

Pesticide spraying, fear-driven killing.

§ Conservation status

According to the IUCN Red List, the western black widow is currently classified as Least Concern.

§ What helps

Shake out shoes left outdoors. Skip pesticides.

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§ Further reading

§ Sources cited

  • American Arachnological Society
  • California Academy of Sciences
  • American Association of Poison Control Centers