Female Black Widow spiders are typically dark brown or shiny black in color when they are full grown adults. They usually exhibit a red or orange hourglass on the underside of the abdomen. Some may have a pair of red spots or have no markings at all. The male widow spiders often exhibit various red or red and white markings on the upper side of the abdomen. These markings will range from a single stripe to bars or spots, and juveniles are often similar to the male pattern. Females of a few species are sometimes a paler brown and some have no bright markings at all. The bodies of black widow spiders range from 3–10 mm in size and some females can measure 13 mm in their body length. This does not include the legs. If you were to include the legs, it would then measure around 25-38 mm.