Button spiders are the black widow's southern African relatives. Two types of button spiders are native to southern Africa: black and brown. The black button spider has four species: east coast button (Latrodectus cinctus), west coast button (Latrodectus indistinctus), inland button (Latrodectus renivulvatus) and karoo button (Latrodectus karooensis). Two species belong to the brown button group: house button (Latrodectus geometricus) and Zimbabwe button (Latrodectus rhodesienses). All button spiders may be identified by their round abdomens -- which are larger than their cephalothoraxes -- and slender legs. Like black widows, button spiders have red hourglass-shaped markings on their abdomens.
Brown widows (Latrodectus geometricus) are native to the Southeast United States, American Southwest and Southern California. These spiders are similar to black widows, but their skin coloration is brown rather than black. Brown widows have the same hourglass-shaped marking on the underside of the abdomen. However, the color of the marking is not always red. Some specimens have orange or yellow markings, which blend in with the spider's brown skin. The legs of brown widows are brown and yellow. Brown widow venom is twice as potent as black widow venom, according to the Florida State Collection of Arthropods.
Endemic to peninsular Florida, red widows (Latrodectus bishopi) are usually found underneath palmetto leaves and sand pine scrubs throughout the Sunshine State. Red widows have dark red legs and cephalothoraxes; the abdomen of the red widow is completely black. This spider does not have an hourglass-shaped marking on its belly, but does have smaller red markings. The top of the red widow's abdomen features red and yellow markings. Although they have a high level of venom, red widows rarely encounter humans and are considered a threatened species in Florida.
The Australian relatives of black widows are redback spiders (Latrodectus hasselti). Female redbacks feature a long red stripe on the top of their abdomen, along with an hourglass-shaped marking on the abdomen's underside. Only female redbacks have red markings. Most female redbacks are black, but some specimens have brown skin. All males are light brown. Males have the same markings as the female, but they are pale in color. Redback webs are funnel-shaped, which differ from the cobwebs built by black widows. In Australia, over 250 cases of redback spider bites happen annually; however, no deaths have ever been documented from redback spider bites.