Male hermit crabs also have a pair of pleopods, which are small appendages located on the underside of their abdomen. These pleopods are used for reproduction, and are not present in female hermit crabs.
Additionally, male hermit crabs typically have a longer and narrower abdomen than female hermit crabs, while female hermit crabs have a shorter and wider abdomen.
These differences can sometimes be subtle, and it can be helpful to compare multiple hermit crabs to get a better idea of the differences between males and females.