The general morphology of this crab is of a dark red/brown color carapace (shell) with white coloration and red spots underneath; can be up to 11.5cm of width (1) . The spot bellied rock crab can be found on the West coast ranging from Washington down to Baja California but are the second most abundant in Southern California with the main distribution found north of Point Conception (2). Males and females are differentiable by careful observation of the abdomen, males possessing a narrower abdomen and females being more broad (2). They also have black tipped claws that also bear a single spine on the wrist. This rock crab is generally active at night and can be found in the low, rocky intertidal zones (1).
(1)Hinton, S. (1987). Seashore life of Southern California: An introduction to the animal life of California beaches south of Santa Barbara (No. 26). Univ of California Press.
(2)Carroll, J.C., R.N. Winn. 1989. Species profiles: Life Histories and environmental requirements of coastal fishes and invertebrates (Pacific Southwest)—brown rock crab, red rock crab, and yellow crab. U.S. Fish and Wildlife Serv. Biol. Rep. 82(11.117).
Photograph: Lovell and Libby Langstroth © California Academy of Sciences