Western Black Widow

Latrodectus hesperus is the western black widow, found from southwestern Canada through the western United States and into Mexico. Adult females are glossy black with a vivid red hourglass on the underside of the abdomen — the most recognizable spider warning marking on Earth. Males are smaller, lighter, with white and red striping, and rarely cause medical concern. The female's venom contains alpha-latrotoxin, a presynaptic neurotoxin that triggers massive neurotransmitter release in mammalian nerves. By weight it's roughly 15× more potent than rattlesnake venom — but the dose is tiny: about 0.06 mg per bite. Symptoms include severe muscle pain, abdominal rigidity, sweating, and hypertension; deaths in modern medical settings are rare. An effective antivenom (Latrodectus antivenin) has existed since 1936. Sexual cannibalism is real in this species — about 2% of mating attempts in the field end with the female consuming the male — but the famously high lab rates were an artifact of confined enclosures with no escape route. Webs are tangled, three-dimensional, and built in concealed spots: woodpiles, garage corners, outdoor furniture, irrigation boxes.