Latrodectus hesperus

Chamberlin & Ivie, 1935

Western black widow, Western black widow spider, Western widow

Latrodectus hesperus is a venomous cobweb spider native to western North America. females are 14–16 mm in length, black with a distinctive red hourglass marking on the ; males are approximately half the size, tan to beige with pale abdominal striping. The constructs irregular, three-dimensional webs with gumfoot threads that capture ground-dwelling prey. Females possess potent neurotoxic venom (α-latrotoxin) that causes latrodectism in humans, though fatalities are extremely rare. The species exhibits facultative group living in fall and winter, with females forming tolerant of 2–8 individuals, then reverting to solitary during spring and summer oviposition.

Latrodectus hesperus by (c) Luke Padon, some rights reserved (CC BY), uploaded by Luke Padon. Used under a CC-BY license.

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Pronunciation

How to pronounce Latrodectus hesperus: //ˌlætrəˈdɛktəs ˈhɛspərəs//

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Identification

Females are reliably identified by the combination of black coloration and red hourglass marking on the lower ; this marking may rarely be yellow or white, and can occasionally be broken or absent. Mature females lack other red markings. Males are tan with pale abdominal striping and swollen . spiders begin life with pale coloration and spots/stripes, darkening with successive . Males mature faster and retain some pale markings. The web architecture is diagnostic: large, irregular, three-dimensional cobwebs with extremely strong, elastic threads that can be plucked like guitar strings without breaking. A funnel-like retreat is typically present.

Images

Habitat

Occurs in diverse including deserts, prairies, and coastal areas; particularly abundant in drier environments but can persist in damp situations. Constructs webs in sheltered locations: rodent burrows, beneath stones and rubble, wood piles, cluttered basements, sheds, garages, and cavities requiring substantial force to access. In urban settings, occupies protected microhabitats with abundant prey. In British Columbia coastal , exhibits seasonal sociality with females forming groups in fall and early winter, living solitarily during spring and summer oviposition.

Distribution

Native to western North America: southwestern Canada (British Columbia to Manitoba), Pacific Coast states, and throughout Texas, Oklahoma, and Kansas in the U.S., extending south into Mexico. Introduced established in Israel, Korea, and parts of Europe; accidental introductions documented in Ireland and Slovakia.

Seasonality

Peak prey capture and female reproductive activity occurs May through October, coinciding with sac production and offspring development. signaling by females peaks during summer when males are most abundant. Seasonal sociality observed in some : group formation in fall and early winter, solitary living during spring and summer oviposition period.

Diet

of arthropods from at least eight orders. In British Columbia, primarily consumes Coleoptera (darkling beetles, weevils, ground beetles) and Hymenoptera (ants, , bumblebees), with peak hymenopteran consumption May through September. Opportunistic cannibal of conspecifics when alternative prey is scarce, when very hungry, or in self-defense during antagonistic encounters. Sibling occurs in spiderlings, with timing varying from 2 days to 3 weeks post-hatching depending on and maternal investment level.