Western Black Widow
Latrodectus hesperus
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Glossy black, bulbous globular abdomen with long, slender legs. Females are significantly larger than males and frequently display the characteristic red hourglass marking on the underside of the abdomen. The cephalothorax is compact and robust relative to the round, fluid-filled abdomen.
Size Estimate
Female body length approximately 8-15 mm with a leg span up to 38 mm; males are much smaller, around 3-6 mm.
Coloration & Markings
Jet black base coloration with high gloss finish. The most prominent marking is a red or orange hourglass-shaped symbol on the ventral side of the abdomen, though juveniles may exhibit white, red, or yellow lateral stripes and spots.
Web Type
Irregular tangle web (cobweb) constructed in dark, undisturbed areas close to the ground, consisting of sticky, scaffolding-like silk threads.
Eye Arrangement
Eight small eyes arranged in two transverse rows of four, typical of the Theridiidae family, with lateral eyes often touching or closely grouped.
Leg Characteristics
Long, slender, smooth legs lacking heavy spination. The hind legs feature a distinctive comb of serrated bristles used to pull silk from the spinnerets and wrap prey.
Venom & Safety Information
Venom Information
Neurotoxic venom containing latrotoxin, which causes massive release of neurotransmitters. Potent relative to humans, though rarely fatal to healthy adults with prompt medical care.
Medical Significance
Medically significant. A bite causes severe local pain followed by painful muscle cramps, abdominal rigidity, sweating, nausea, and tremors. Seek medical attention immediately if bitten.
Safety Recommendations
Wear gloves when clearing dark, undisturbed outdoor areas like woodpiles or sheds. Inspect shoes and gardening tools before use. Relocate spiders outdoors using a container if found inside.
Habitat & Behavior
Habitat & Range
Found throughout western North America. Prefers dry, dark, sheltered microhabitats such as woodpiles, rock crevices, crawl spaces, garage corners, and under outdoor furniture.
Behavior & Temperament
Reclusive, non-aggressive, and nocturnal. They typically retreat to a hiding spot when disturbed and will only bite defensively when trapped, squeezed, or accidentally compressed against human skin.
Diet & Prey
Primarily feeds on crawling and flying insects such as beetles, flies, mosquitoes, grasshoppers, and other spiders caught in its sticky web snare.
Seasonal Activity
Most active during the warmer spring and summer months, during which mating and web expansion peak. They overwinter in sheltered adult or sub-adult stages.
Description
The Western Black Widow is one of North America's most recognizable and misunderstood spiders. Featuring a striking glossy black body offset by a vibrant red hourglass, this reclusive cobweb weaver prefers quiet, dark retreats. While its neurotoxic venom demands respect, the spider is fundamentally non-aggressive, serving as an effective natural controller of pest insect populations around human habitations.
Key Features
Glossy black globular abdomen, ventral red hourglass marking, irregular cobweb structure, and slender legs with a comb-like structure on the hind tarsi.
Similar Species
False black widows (Steatoda grossa), which lack the red hourglass and have a more leather-like, brownish sheen; Male black widows, which are smaller and patterned with red and white.
Life Cycle
Females construct pear-shaped silk egg sacs containing hundreds of eggs. Spiderlings disperse via ballooning after hatching. Females can live up to 1-3 years, while males have much shorter lifespans.
Ecological Importance
Acts as an apex predator among household and garden arthropods, naturally regulating populations of flies, beetles, and other potential insect pests.
Conservation Status
Not evaluated by the IUCN, but populations are widespread, highly resilient, and generally considered secure across their native range.
Interesting Facts
The female's comb-like hind legs are specially evolved to handle silk and wrap prey with remarkable speed. Sexual cannibalism, where the female consumes the male after mating, is occasionally observed in nature.
Photography Tips
Use a macro lens with a flash for lighting detail. Maintain a safe distance, use a tripod for stability, and focus on capturing the ventral side to clearly show the red hourglass marking.
User Notes
On wall
Identified: 2026-10-10T21:00:29.103117