Western Black Widow
Latrodectus hesperus
Theridiidae (Cobweb Spiders), Order Araneae. Characterized by comb-like setae on the fourth pair of tarsi used to pull silk over prey.
Physical Description
Glossy black, bulbous abdomen, slender legs, and typical sexual dimorphism with females being much larger and darker with the iconic red marking, while males are smaller, lighter, and often striped.
Size Estimate
Body length of the female is roughly 8 to 13 millimeters with a leg span up to 38 millimeters; males are significantly smaller.
Coloration & Markings
Jet-black body with a characteristic red or orange hourglass-shaped marking on the ventral side of the abdomen, sometimes varying to spots or broken shapes.
Web Type
Irregular, sticky tangle web (cobweb) constructed close to the ground in dark, undisturbed sheltered areas.
Eye Arrangement
Eight small eyes arranged in two horizontal rows of four, typical of the cobweb spider family.
Leg Characteristics
Long, slender, smooth black legs without prominent spines, featuring comb-like serrated bristles on the hind tarsi.
Venom & Safety Information
Venom Information
Neurotoxic venom containing latrotoxin, which affects the nervous system and causes intense pain and muscle cramps.
Medical Significance
Medically significant; bites can cause severe pain, muscle rigidity, abdominal cramps, sweating, and nausea, requiring medical evaluation.
Safety Recommendations
Wear gloves when working around woodpiles or outdoor hardware, shake out shoes and clothing left outside, and safely relocate spiders using a jar if found indoors.
Habitat & Behavior
Habitat & Range
Found throughout western North America in dry, dark, sheltered microhabitats such as woodpiles, under rocks, and around outdoor structures like fences and gates.
Behavior & Temperament
Reclusive, non-aggressive, and timid; retreats when disturbed and only bites in self-defense when trapped or pressed against human skin.
Diet & Prey
Insects including flies, mosquitoes, beetles, grasshoppers, and other spiders captured in its sticky tangle web.
Seasonal Activity
Most active during warmer spring and summer months, often seeking shelter indoors or in protected structures as cooler weather approaches.
Description
The Western Black Widow is a reclusive architect of tangled webs found in sheltered outdoor nooks. Famous for its glossy black body and warning red hourglass, it plays a vital role in insect control despite its potent neurotoxic venom.
Key Features
Glossy jet-black coloration combined with a distinct red or orange ventral hourglass marking and an irregular cobweb.
Similar Species
False black widows (Steatoda grossa) lack the bright red hourglass marking and have a more brownish, less glossy appearance.
Life Cycle
Females produce multiple pear-shaped silk egg sacs containing hundreds of eggs. Spiderlings disperse via ballooning after hatching. Lifespan is up to several years for females.
Ecological Importance
Acts as an effective natural pest controller by regulating populations of various insects and agricultural pests.
Conservation Status
Secure and widespread, with stable populations across its native range experiencing no immediate threats.
Interesting Facts
Despite their fearsome reputation, black widows rarely bite unless directly compressed, and females occasionally consume males after mating, though not invariably.
Photography Tips
Use macro lenses with adequate natural side lighting or a diffuser to capture the glossy texture and ventral hourglass marking without provoking a defensive reaction.
Identified: 2026-08-30T20:14:43.410397