Latrodectus mirabilis, sometimes (but rarely), known as black widow is a spider species that is native to most of South America in the genus Latrodectus of the family Theridiidae.
Instead of an 'hourglass' pattern on the ventral side of this species, unlike other Latrodectus species, This spider has a red rectangle on it's ventral side.
This spider's bite has never been recorded but as with other Latrodectus species most people think it's bites are venomous and Latrodectism happens when bitten.
The False Black Widow looks more like this species than any other in Latrodectus except the Brown Widow