Western Black Widow
Latrodectus hesperus
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Small to medium-sized spider with a globular, shiny abdomen and a relatively small cephalothorax. Females are robust with long, slender legs, while males are much smaller, lighter built, and typically harmless.
Size Estimate
Females have a body length of about 8 to 13 mm and a leg span up to 38 mm. Males are considerably smaller, around 3 to 5 mm in body length.
Coloration & Markings
Females are glossy jet black with a distinctive red or orange hourglass marking on the underside of the abdomen, sometimes accompanied by red spots or dorsal stripes depending on maturity. Males are lighter brown or gray with lighter banding.
Web Type
Irregular tangle web (cobweb) constructed near ground level in dark, sheltered areas like corners, crevices, under rocks, or around building foundations.
Eye Arrangement
Eight small eyes arranged in two rows of four, typical of the family Theridiidae, with lateral eyes often touching.
Leg Characteristics
Legs are long, slender, smooth, and glossy black, lacking heavy spination but equipped with a comb-like row of serrated bristles on the fourth tarsus used to pull silk over prey.
Venom & Safety Information
Venom Information
Contains a potent neurotoxin called alpha-latrotoxin which affects the nervous system, causing neurotransmitter release.
Medical Significance
Medically significant. Bites from adult females can cause severe local pain, muscle cramps, rigidity, abdominal pain, nausea, and sweating. While rarely fatal to healthy adults, medical attention should be sought if bitten.
Safety Recommendations
Wear gloves when cleaning out dark corners, garages, or handling firewood. Inspect shoes and clothing left outdoors. If bitten, clean the wound, apply ice, and seek medical evaluation.
Habitat & Behavior
Habitat & Range
Found throughout western North America, inhabiting arid and temperate regions. Prefers dark, dry, sheltered microhabitats such as woodpiles, rock crevices, garages, crawl spaces, and outdoor furniture.
Behavior & Temperament
Non-aggressive and timid, typically hiding in its web retreat during the day. Biting is strictly a defensive reaction when accidentally pressed against human skin or when a female fiercely guards her egg sac.
Diet & Prey
Feeds primarily on crawling and flying insects such as flies, mosquitoes, beetles, grasshoppers, and other spiders trapped in its sticky web.
Seasonal Activity
Most active during the warmer months from spring through autumn, with mating typically peaking in late spring and summer.
Description
The Western Black Widow is one of North America's most recognizable spiders. Known for its glossy black body and the iconic red hourglass marking, it favors quiet, undisturbed corners of human structures and natural crevices alike. Though notorious for its potent neurotoxin, it is inherently shy and prefers to flee or play dead rather than bite.
Key Features
Glossy black body, bright red or orange hourglass marking on the ventral abdomen, and construction of an irregular, messy cobweb in dark, sheltered locations.
Similar Species
False black widows (Steatoda grossa), which lack the red hourglass marking and have a more purplish-brown, matte appearance.
Life Cycle
Females produce multiple pear-shaped silk egg sacs containing hundreds of eggs each season. Spiderlings disperse via ballooning. Females can live for up to three years.
Ecological Importance
Serves as an effective natural predator of nuisance insects and pests around homes and agricultural areas, contributing to natural population control.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and highly adaptable to human-modified environments.
Interesting Facts
Despite their fearsome reputation, male black widows and juveniles are completely harmless to humans. Females sometimes practice sexual cannibalism, consuming the male after mating.
Photography Tips
Use a macro lens with a tripod and a diffused flash to capture the glossy texture and underside markings safely from a distance of at least 30 centimeters.
Identified: 2026-10-10T21:01:43.518639