After they shed their shells several times, they return to land where they dig holes to live in. They pile the excavated sand outside, and the result looks like small chimneys. A young crab develops into an adult in a year.
潮汐區裡的螃蟹，幼蟲必需回到海洋生活，經過多次脫殼後，再一隻隻回到海岸，鑿洞定居，它們挖出的泥，就堆置在洞穴外，像個小煙囪，小螃蟹經過一年就可以長為成蟹。