The hermit crab is a crustacean, but it is very different from other crustaceans. While most crustaceans are covered from head to tail with a hard exoskeleton, the hermit crab is missing part of its exoskeleton. The back part where its abdomen is located, is soft and squishy. Thus, the minute a hermit crab molts into an adult, it sets out to find a shell in which to live.