I have no idea of the real name of this crab, but they are a little shy - will hide in the shadow of a rock if they feel you are a little too close. They are hunted by sea-birds, so predators looming over them give them the heebie-jeebies. Otherwise, they allow humans surprisingly close. They have a beautiful light blue under the chin at the join of the legs to the body ( slightly visible here). These were photographed on Santa Cruz, but they are widespread over the islands.