The female black widow spider is considered the most venomous spider in North America. The venom of the black widow spider is 15 times as toxic as the venom of the prairie rattlesnake.

Only the female black widow is dangerous to humans; males and juveniles are harmless. The female black widow will, on occasion, kill and eat the male after mating. More than 35,000 species of spiders occur worldwide. About 3,400 species of spiders in 64 families are found in North America.