Viúva-negra (Latrodectus mactans) is the Black Widow spider, name given generally to the spiders of the genus Latrodectus. The Viúva-negra is a species of spider distributed across America. In Brazil it is found in the Atlantic Forest near the sea, especially in beaches. The female has a shiny black color, with large red patch in the shape of an hourglass on the ventral surface of the abdomen, and about 1 cm in length. The name comes from the fact that the female usually eat the male after copulation. Their bite is often fatal. Being a well-known spider in Brazil and by knowing that their venom is very strong, there is a hint that this is the most poisonous spider.