Western Black Widow, Black Widow Spider
Latrodectus hesperus
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a globular abdomen, comb-like serrated setae on the fourth tarsus used for flinging silk over prey, and building irregular, tangled three-dimensional webs.
Physical Description
The spider possesses a compact cephalothorax and a distinctly large, glossy, spherical abdomen. Females are robust with slender legs, while males are much smaller and feature distinct markings. The texture appears smooth and shiny with a jet-black coloration.
Size Estimate
Body length of the adult female is approximately 8-13 mm, with a leg span of roughly 38-50 mm. This specimen is an adult female.
Coloration & Markings
Glossy jet-black overall coloration with no dorsal patterns visible from this angle. Often features a characteristic red or orange hourglass marking on the ventral side of the abdomen, though some individuals may have spots or broken lines.
Web Type
Irregular cobweb or tangle web consisting of sticky, haphazardly arranged silk threads built close to the ground or within dark, sheltered crevices.
Eye Arrangement
Eight small eyes arranged in two transverse rows of four, typical of the family Theridiidae, with lateral eyes often touching or closely spaced.
Leg Characteristics
Long, slender, smooth black legs without prominent spines, featuring specialized comb structures on the hind tarsi for manipulating silk.
Venom & Safety Information
Venom Information
Contains latrotoxin, a potent neurotoxin that affects the nervous system. The venom is significantly potent, though fatalities are extremely rare with modern medical care.
Medical Significance
Medically significant. A bite causes severe local pain followed by muscle cramps, rigidity in the abdomen, sweating, nausea, and general malaise. Immediate medical attention should be sought if bitten.
Safety Recommendations
Wear gloves when clearing dark, undisturbed outdoor areas like woodpiles or sheds. If found indoors, relocate the spider safely using a jar and stiff paper, or contact professional pest control if near high-traffic living areas.
Habitat & Behavior
Habitat & Range
Western North America, inhabiting dry, dark, sheltered microhabitats such as woodpiles, rock crevices, under eaves, garage corners, and crawl spaces.
Behavior & Temperament
Reclusive and non-aggressive. They spend most of their time stationary in their webs. They bite defensively only when directly pressed, squeezed, or accidentally trapped against human skin.
Diet & Prey
Generalist predators feeding primarily on crawling and flying insects such as flies, beetles, grasshoppers, ants, and occasionally other spiders caught in their sticky web.
Seasonal Activity
Most active during the warm spring and summer months, with mating peaking in late spring. They overwinter as adults or older juveniles in sheltered protected nooks.
Description
The Western Black Widow is a reclusive architect of tangled webs, instantly recognized by its glossy black, spherical abdomen. While famously venomous, it prefers to retreat rather than confront humans, playing a vital role in natural insect regulation.
Key Features
Glossy black, spherical abdomen, slender legs, timid web-dwelling behavior, and often the telltale red hourglass marking on the underside.
Similar Species
False black widows (Steatoda grossa) which lack the red hourglass and have a more brownish, leather-like sheen, and male black widows which are smaller and patterned.
Life Cycle
Females produce multiple papery, pear-shaped egg sacs containing hundreds of eggs each season. Spiderlings disperse via ballooning. Females can live up to three years, while males have a much shorter lifespan and die shortly after mating.
Ecological Importance
Acts as an effective natural predator of pest insect populations, helping balance local arthropod ecosystems.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and widespread across their natural range.
Interesting Facts
Black widows possess silk that is remarkably strong and elastic. Females occasionally practice sexual cannibalism, consuming the male after mating, which gives the species its ominous reputation.
Photography Tips
Photograph from a safe distance using a macro lens. Avoid touching or disturbing the web. Natural side lighting highlights the glossy texture and helps capture diagnostic markings without the harsh glare of a flash.
Identified: 2026-08-06T16:54:16.386013