Black Widow

The black widow is the most venomous spider in the U.S.
People rarely die from black widow spider bites, since the amount of venom injected is so small. The adult female black widow is venomous. Males and juveniles are usually harmless, having smaller quanities of venom as compared to the female.
The female black widow spider is sometimes referred to as the "hourglass" spider because the red marking on her belly is often in the shape of an hourglass. Sometimes it may look like two triangles.