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"Black Widow" (Latrodectus hesperus)
black widow DESCRIPTION: L=0.5-0.75" (12-19mm) in females; males less than half size of female. Female has black, bulbous body with redish to yellowish hourglass marking underneath. Male is brown with lighter markings on legs and abdomen.
NATURAL HISTORY: Females are Dangerously Venomous (potentially fatal -- when stung, call the
Arizona Poison and Drug Information Center at 626-6016 in Tucson and 1-800-362-0101 elsewhere in Arizona.). Males are too small to be dangerous to humans. The venom is neurotoxic, often causing severe pain, nausea, dizziness, and cramps (rarely death). Black Widows are found in natural habitats, but commonly occur in and around people's houses, buildings, and woodpiles. They build strong, irregular webs which they use to capture their arthropod prey. Females usually do not venture from their web, are quick to retreat, but will bite in self-defense. A male, being potential prey to the larger female, must approach the female carefully when attempting to mate with the female. The male will come to the edge of the web and tap out a signal to the female that his intentions are mating not becoming eaten. Eventually the male will walk onto the web and approach the female (ready to retreat if necessary). Following mating, the male attempts an escape, but often fails (thus the name black widow). Nonetheless, black widows only mate once in their life. The female stores the sperm to fertilize her subsequent sets of eggs (egg sacs made of her silk) over the next 1-2 years of her life.