A baby black widow has a white abdomen with black spots in addition to brown legs and a tan cephalothorax, the part of a spider to which the legs attach. This coloration is dramatically different from the well-known female adults, making the young more difficult to identify.
The colors and patterns of the adult females begin to change with each moult, when the spiders outgrow their current exoskeletons. Eventually, females turn black, and the area where the red hourglass figure appears on the underside of the abdomen changes from white to yellow to orange and finally red. Males, though, tend to keep the coloration with which they are born.