Black widow spiders have earned a fearsome reputation for their venomous bite. But in parts of the southern United States these spiders have much to fear themselves—from spider relatives who really don’t like their company. In the past couple decades, researchers have noticed southern black widow spiders (Latrodectus mactans, adult female shown at right) commonly being displaced by the brown widow (Latrodectus geometricus, adult female at left), a fellow species in the same genus. But new research suggests this isn’t a just simple case of one species winning the competition for food or habitat. Instead, a study shows brown widow spiders have a striking propensity to seek out and kill nearby black widows. (Note: Images are not shown to matching scale and thus do not reflect relative sizes of the two spiders.) (Photo by Louis Coticchio)