Coconut Crab (Birgus latro) is the largest terrestrial arthropod in the world. It is known for its ability to crack coconuts with its strong pincers in order to eat the contents. It is sometimes called the robber crab because some coconut crabs are rumored to steal shiny items such as pots and silverware from houses and tents.
The second photo gives you a good idea of how large these crabs are - a coconut crab is seeking food from a black dustbin.