The widow spiders are members of the spider genus Latrodectus, in the family Theridiidae.
Latrodectus includes approximately 31 recognized venomous species, with the black widow spider (Latrodectus mactans) being the best known member of the group.
The female black widow's venom is particularly harmful to humans (males almost never bite humans).
Spiders of the genus Steatoda (also of the Theridiidae family) are often mistaken for widow spiders, and are known as false widow spiders.
The false widow spiders are significantly less harmful to humans..
For more information about the topic Widow spider, read the full article at Wikipedia.org, or see the following related articles:
Note: This page refers to an article that is licensed under the GNU Free Documentation License. It uses material from the article Widow spider at Wikipedia.org. See the Wikipedia copyright page for more details.

