Western Black Widow, Shoebox Spider, Tangle-web Spider
Latrodectus hesperus
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include comb-like setae on the tarsus of the fourth leg used to pull silk over prey.
Physical Description
Features a glossy, jet-black, globose abdomen and a smaller, distinct cephalothorax. The body is smooth and bulbous without prominent hairiness. This specimen displays the classic adult female silhouette with a rounded, shiny abdomen.
Size Estimate
Body length is approximately 8 to 13 mm for an adult female, with a leg span of about 38 mm. This matches an adult female specimen.
Coloration & Markings
Intense, glossy jet-black overall. While the dorsal surface of the adult female is typically all black, a red or orange hourglass-shaped marking is usually present on the ventral (underside) of the abdomen, though some variations may show red spots or a broken stripe.
Web Type
Irregular, three-dimensional tangle web, commonly known as a cobweb. Constructed near the ground in dark, undisturbed corners, featuring sticky, tension-laden vertical lines designed to entangle walking insects.
Eye Arrangement
Eight small, dark eyes arranged in two rows of four, typical of the Theridiidae family, positioned on the front of the cephalothorax.
Leg Characteristics
Long, slender, glossy black legs without prominent banding or heavy spination. The fourth pair of legs features a comb of serrated bristles used for wrapping prey.
Venom & Safety Information
Venom Information
Contains a potent neurotoxin called alpha-latrotoxin, which affects the nervous system by causing massive neurotransmitter release. Potent relative to humans, though rarely fatal with modern medical care.
Medical Significance
Medically significant. A bite can cause severe local pain followed by muscle cramps, abdominal rigidity, sweating, nausea, and tremors. Seek medical attention immediately if bitten, though antivenom and supportive care are highly effective.
Safety Recommendations
Wear gloves when moving stored items, firewood, or working in dark corners. If found indoors, gently guide the spider into a container using a broom or card to relocate it safely outdoors away from high-traffic zones.
Habitat & Behavior
Habitat & Range
Found across western North America. Prefers dark, dry, sheltered microhabitats such as under rocks, in woodpiles, basements, crawlspaces, and around buildings near ground level.
Behavior & Temperament
Reclusive, non-aggressive, and nocturnal. They typically retreat to a hiding spot near their web when disturbed and only bite defensively when pressed directly against skin.
Diet & Prey
Consists primarily of crawling insects such as beetles, ants, cockroaches, and grasshoppers, as well as occasional woodlice and other spiders captured in the sticky web.
Seasonal Activity
Most active during the warm summer and autumn months when mating occurs. They overwinter as adults or older juveniles in sheltered crevices.
Description
The Western Black Widow is one of North America's most recognizable spiders due to the female's striking glossy black body and warning coloration. Reclusive by nature, they play an important ecological role in controlling insect populations while requiring cautious coexistence.
Key Features
Glossy black coloration, globose abdomen shape, and the ventral red hourglass or spot markings combined with an irregular tangle web near the ground.
Similar Species
False black widows (Steatoda grossa) lack the hourglass marking and have a more purplish-brown, less glossy appearance; male black widows are much smaller and feature brown-and-white banding.
Life Cycle
Females construct pear-shaped silk egg sacs containing hundreds of eggs. Spiderlings disperse via ballooning. Females can live up to three years, whereas males have a much shorter lifespan and undergo sexual cannibalism on occasion.
Ecological Importance
Acts as an effective natural predator of pest insects, helping to regulate populations of crawling bugs in both natural and domestic environments.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and widespread throughout their native range.
Interesting Facts
Despite their fearsome reputation, black widows are timid and prefer to play dead or flee rather than bite. The venom is primarily evolved to subdue invertebrate prey rather than defend against large mammals.
Photography Tips
Use a macro lens with a flash or good side lighting to capture the glossy texture and underside markings. Maintain a safe distance and avoid touching or provoking the specimen.
Identified: 2026-10-06T03:08:14.189832