The black widow spider (Latrodectus) is widely recognized for its potent neurotoxic venom and the signature red hourglass marking on the female’s abdomen. Black widows cannot jump. These spiders are not built for leaping and do not employ jumping for locomotion, hunting, or defense. Their movement is adapted for life within a specialized web structure.
How Black Widows Move
Black widow spiders are sedentary ambush predators that spend their lives anchored within their webs. Their primary mode of movement is a slow walk across the silk strands or a quick dash when subduing entangled prey or retreating to their shelter. They lack the specialized leg musculature necessary to propel themselves through the air for any distance.
The spider relies on its cobweb to capture its meals. When a small insect is caught, the spider detects the vibrations through its legs. It then uses its hind legs, which possess a comb-like row of bristles, to fling silk over the prey, securing it before delivering a venomous bite.
Cobweb Spiders Versus Jumping Spiders
The common confusion about the black widow’s ability to jump stems from its being mistaken for other spider species. Black widows belong to the family Theridiidae, commonly known as cobweb weavers or comb-footed spiders. Spiders in this family are characterized by poor eyesight and a reliance on their webs as an external sensory system.
True jumping spiders, which do leap, are members of the family Salticidae. These spiders are active hunters that do not build webs to catch prey, instead using their exceptional vision to stalk and pounce. Salticidae possess enlarged anterior median eyes that provide stereoscopic color vision, allowing them to accurately judge the distance for a precise leap.
Understanding the Bite Risk
The danger comes from the neurotoxin alpha-latrotoxin in the female’s venom, not from aggressive pursuit or jumping. This venom causes a condition called latrodectism, characterized by systemic effects in humans. Common symptoms include severe muscle pain, cramping, abdominal rigidity, and nausea.
Bites almost exclusively occur when the spider is accidentally disturbed or pressed against human skin while seeking refuge in a dark, secluded space, such as a shoe or gardening glove. The spider’s natural instinct when threatened is to drop from its web and play dead, rather than to attack. While the venom is potent, the amount injected is rarely life-threatening to a healthy adult, and most reported bites do not require medical intervention.