Western Black Widow
Latrodectus hesperus
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Globular, bulbous abdomen that is significantly larger than the cephalothorax. The exoskeleton is smooth and glossy. This specimen appears to be an immature female based on the orange-tinted dorsal markings and slightly translucent legs.
Size Estimate
Body length 5-10mm (immature); adult females reach 14-16mm. Leg span roughly 25-30mm.
Coloration & Markings
Deep charcoal to black body. This juvenile shows a visible orange/red longitudinal stripe or series of spots on the dorsal (top) side of the abdomen, which typically fades to solid black in adults. The classic red hourglass is on the ventral (underside).
Web Type
Irregular, tangled 'cobweb' made of exceptionally strong silk. Built in dark, recessed areas, often near the ground or in corners.
Eye Arrangement
Eight eyes in two horizontal rows. Not easily visible in this photo, but characteristic of Theridiidae with small, dark eyes.
Leg Characteristics
Long, slender legs. The first and fourth pairs are the longest. Immature specimens often have tan or banded legs that darken to solid black with maturity.
Venom & Safety Information
Venom Information
Contains alpha-latrotoxin, a potent neurotoxin. It affects the nervous system by causing a massive release of neurotransmitters.
Medical Significance
Medically significant. Bites cause 'latrodectism,' characterized by localized pain, muscle cramping, abdominal pain, and sweating. While rarely fatal to healthy adults, medical attention is advised for children or the elderly.
Safety Recommendations
Wear gloves when moving wood or cleaning dark corners. If bitten, stay calm, ice the area, and seek medical evaluation. Do not attempt to handle with bare hands; use a glass and paper for relocation.
Habitat & Behavior
Habitat & Range
Common throughout Western North America, from Canada to Mexico. Prefers dark, undisturbed places like woodpiles, garages, crawlspaces, and outdoor furniture.
Behavior & Temperament
Reclusive and non-aggressive. They spend most of their time hanging upside down in the web. They typically bite only when squeezed or defended when their web is disturbed.
Diet & Prey
Insects like crickets, beetles, and flies. They use 'comb feet' to wrap prey in sticky silk before delivering a paralyzing bite.
Seasonal Activity
Most active in late summer and autumn when females reach full maturity and mate.
Description
A striking and widely recognized spider, the Western Black Widow is an essential predator in the western US. While feared for its potent neurotoxic venom, it is a shy architect of messy but incredibly strong silk structures.
Key Features
Glossy black globular abdomen, red/orange dorsal stripes (juvenile) or ventral hourglass (adult), and unusually high silk strength.
Similar Species
Steatoda grossa (False Black Widow), which lacks the red markings and has a more purple-brown tint.
Life Cycle
Females produce papery, tan egg sacs containing hundreds of eggs. Spiderlings disperse via ballooning. Females can live up to 3 years; males much shorter.
Ecological Importance
Highly effective at controlling populations of agricultural pests and nuisance insects like cockroaches and flies.
Conservation Status
Not listed / Secure. Common throughout its natural range.
Interesting Facts
The silk of a black widow is one of the strongest natural fibers known, with a tensile strength comparable to high-grade steel.
Photography Tips
Focus on the abdomen markings. Use a macro lens to capture the glossy texture. Avoid disturbing the web as they will retreat into a crevice.
Identified: 2026-05-17T19:31:30.899895