: a venomous New World spider of the genus Latrodectus (L. mactans) the female of which is black with an hourglass-shaped red mark on the underside of the abdomen
Any of several black spiders in the genus Latrodectus with a venomous bite that is rarely fatal to humans. Black widow species are found worldwide, with three living in North America. In Australia it is called the redback. The females are shiny black, usually with a reddish hourglass-shaped design on the underside of the spherical abdomen and with a body about 1 in. (2.5 cm) long. The black widow preys on insects. The male, about one-fourth the female's size, is often killed and eaten by the female after mating (the source of its name).