As the picture shows, the male black widow spider is 1/3 inches smaller than its mate (and weights thirty times less). If compared, the male has longer and thinner legs and its body is much more tube-shaped than the female’s. It does not have the red hourglass "onboard". Instead, it has a tiny –almost invisible - red spot under his abdomen.
This picture shows the main difference between male and female black widow arachnids.