[1][3] It was transferred to the genus Latrodectus in 1837 by Charles Walckenaer and is currently placed in the family Theridiidae of the order Araneae.

As a result, there exist numerous references which claim that "black widow" (without any geographic modifier) applies to L. mactans alone.

[5] Females are shiny and black in color, with a red marking in the shape of an hourglass on the ventral (under) side of her very rounded abdomen.

[7] Juveniles have a distinctly different appearance from the adults; the abdomen is grayish to black with white stripes running across it and is spotted with yellow and orange.

[8] The southern widow is primarily found in (and is indigenous to) the southeastern United States, ranging as far north as Ohio and as far west as Texas.

[9] The northern black widow (L. variolus) is found primarily in the middle Atlantic states, though its range overlaps with that of L. mactans.

Black widow spiders reproduce sexually when the male inserts his palpal bulbs into the female's spermathecal openings.

[citation needed] Black widow spiders typically prey on a variety of insects; however, they also consume woodlice, diplopods, chilopods, and other arachnids.

[19] There are various parasites and predators of widow spiders in North America, though apparently none of these have ever been evaluated in terms of augmentation programs for improved biocontrol.

Parasites of the egg sacs include the flightless scelionid wasp Baeus latrodecti,[20] and members of the chloropid fly genus Pseudogaurax.

[citation needed] Other organisms including mantises or centipedes also will occasionally and opportunistically take widows as prey, but the preceding all exhibit some significant specific preference for Latrodectus.

The venom injected by the female black widow is known as alpha-latrotoxin which binds to receptors at the neuromuscular motor end plate of both sympathetic and parasympathetic nerves, resulting in increased synaptic concentration of catecholamines.