Black Widow and Redback spiders look similar, but a few key differences help you tell them apart. Black Widows, found mostly in North America, have a shiny black body with a red hourglass marking on the underside of the abdomen. Redbacks, common in Australia, have a black body with a distinct red stripe on top of the abdomen. Both are venomous and build messy, irregular webs, but Black Widows tend to move around more, while Redbacks usually stay in one spot. Although both bites can be serious, modern treatment has made Redback bites less dangerous today.