Black widows are color-coded to deter predators without tipping off prey. Duke Today, Feb. 29, 2016. Secret codes and hidden messages aren’t just for computer security experts or kids passing notes in class — animals use them too. The telltale red hourglass of the black widow spider appears brighter and more contrasting to birds than to insects, finds a new study. The red-and-black color combination sends a “beware!” signal to predators without scaring off their prey. Picked up by Forbes, Smithsonian Magazine, Discovery News and the Daily Mail.