large, nocturnal land crab of the southwest Pacific and Indian oceans. It is closely related to the hermit crab, belonging to the same family, Coenobitidae (order Decapoda of the class Crustacea). Adults are about 1 m (about 40 inches) from head to tail and weigh about 4.5 kg (10 pounds). The full-grown adult crab ranges in colouring from light violet to brown and deep purple. Young adults are brown, with black stripes on their legs. The crab uses two large chelae, or pincers, to pound or chip open coconuts-the soft white meat of which is its principal diet. Although robber crabs can climb trees, they apparently eat only coconuts already on the ground
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