crab bottom drawing

Bottom view of crab shows the difference in abdominal width (area) between males (left, narrow) and females (right, wide).

female crab bottom

Female crab showing the wide carapace.

Photo by Christian Fischer through Wiki Commons

key characteristics

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:

  • One of very few crabs in North America found in freshwater.
  • Adults and juveniles (>1 inch) have furry white-tipped claws that are equal in size. Juveniles with a carapace length less than one inch may not have hair on their claws but those over one inch will have hair.
  • Light brown to olive green body (carapace) that is 3 to 4 inches wide in adults. The carapace is smooth and round and has a 4 lateral spines (behind each eye), although the forth spine may be small.
  • There is a U-shaped notch in the carapace between the crab’s eyes.
  • This crab has four sharp-tipped walking legs and a claw on each side, but lacks a modified swimming leg or paddle (such as those on blue crabs). The legs are over twice the length of the carapace.