Black Widows are found in many areas of the United States, but they are most common in the South. This spider prefers a dark, damp habitat. It is most often found outside, but can be found inside in dark places inside dwellings such as sheds, garages, and closets. The female rarely leaves the web and will bite only when she is bothered. The small, oval egg cases are tan in color, papery in texture and are found hanging in the web.
http://www.spiderroom.info/va_blackwidowspider.html
The venomous bite of these spiders is considered particularly dangerous because of the neurotoxin latrotoxin, which causes the condition latrodectism, both named for the genus. The female black widow has unusually large venom glands and her bite can be particularly harmful to humans. However, despite the genus' notoriety, Latrodectus bites are rarely fatal.
https://en.wikipedia.org/wiki/Latrodectus
Identification. The brown widow is highly variable in color. It may be almost white to almost black. Typically, it is a light to medium brown, with an orange-to-yellow hourglass marking on the underside of the abdomen; the coloration of the hourglass often is a good indication of this species. The leg segments are banded, with one half of each segment lighter in color than the other half.
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1 Latrodectus geometricus, the brown widow, grey widow, or brown button spider is found in Africa, USA, South America, and Australia.
https://en.wikipedia.org/wiki/Latrodectus
Spiders of the genus Steatoda (also of the Theridiidae family) are often mistaken for widow spiders, and are known as  false widow spiders ; they are significantly less harmful to humans.
https://en.wikipedia.org/wiki/Latrodectus
It is highly recommended that people leave this spider alone; observe, but don't touch. The brown widow is an extremely timid spider which has rarely been reported to bite. For more general information about all types of Widow spiders, please refer to the Latrodectus genus info page. Precautions: Be very careful when working around areas where widow spiders may be established.
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Other Common Names. Black Widow-The L. mactans is often considered the original Black Widow. “The Hourglass Spider” because of the red hourglass shaped mark on the female’s abdomen. “The Shoe Button Spider” due to the form of the spider’s jet-black abdomen.
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Black widows are spiders. Their scientific name is Latrodectus mactans, and they share the Latrodectus name with several similar spiders (sometimes called widow spiders). They are shiny black and have round abdomens with a red hourglass pattern on its underside. They are closely related to another group called Steotoda (sometimes called false widow spiders) that contains species that are not dangerous to humans.
https://simple.wikipedia.org/wiki/Black_widow
This spider has been given its name because of the misconception that the female always eats the male after mating. Sometimes the male escapes unharmed. The Black Widow is a member of the cobweb weaver family. The female Black Widow is 3/8 inch long and has legs and cephalothorax that are black. Its teardrop shaped abdomen is shiny black with a red hourglass mark on the underneath side. The hourglass is easy to see because the spider hangs upside down in the tangled, but strong web. Sometimes there is a red spot near the spinnerets and even small red streaks or spots on the back of the abdomen. The harmless male of the species is 1/8 inch long, with red and white markings on the abdomen.
http://www.spiderroom.info/va_blackwidowspider.html
The genus contains 32 recognized species distributed worldwide, including the North American black widows (L. mactans, L. hesperus, and L. variolus), the button spiders of Africa, and the Australian redback.
https://en.wikipedia.org/wiki/Latrodectus
what is the latrodectus habitat
The brown widow, grey widow, or brown button spider is found in Africa, USA, South America, and Australia. The latrodectus is found in Africa, the United States, South America, and Australia.