The male and female crabs are identified mainly by observing the belly button and the hair on their legs. The belly button of male crab is pointed, a bit like a triangle, and there are dense fluff on eight legs. The belly button of the female crab is relatively round, the abdomen is oval, and only the first two legs have fine fluff. Life habits of crabs crabs generally inhabit wet places and live in seawater or fresh water. A few crabs can adapt to land life.
Most crabs are omnivores and usually feed on aquatic plants, organic debris and animal carcasses. Some crabs also prey on fish, shrimp or smaller molluscs.
Crab is a kind of nocturnal animal. It usually lives in caves or seclusion. When there are no cave living conditions in the environment, it hides in stones or haystacks. （PangXieGongMuZenMeOuFen）