Bottom view of crab shows the difference in abdominal width (area) between males (left, narrow) and females (right, wide). Female crab showing the wide carapace.
Photo by Christian Fischer through Wiki Commons
Adult crab indicting the hairy claws, notch between the eyes, and the four spines along the carapace.

Adult mitten crabs are easy to identify because their claws appear to have distinctive thick fur that looks like mittens, a trait for which they are named. The main identifying characteristics are: