The next three pairs have smaller tweezer-like chelae at the end, and are used as walking limbs.
In addition these specially adapted limbs enable the coconut crab to climb vertically up trees (often coconut palms) up to 6 m high.
The coconut crab (Birgus latro) is the largest terrestrial arthropod in the world.
It is a derived hermit crab which is known for its ability to crack coconuts with its strong pincers in order to eat the contents.
The body of the coconut crab is, like all decapods, divided into a front section ( cephalothorax), which has 10 legs, and an abdomen.
The front-most legs have massive claws used to open coconuts, and these claws (chelae) can lift objects up to 29 kg (64 lb) in weight.
Although Birgus latro is a derived type of hermit crab, only the juveniles use salvaged snail shells to protect their soft abdomens, and adolescents sometimes use broken coconut shells to protect their abdomens.
They contain a tissue similar to that found in gills, but suited to the absorption of oxygen from air, rather than water.
The last pair of legs is very small and serves only to clean the breathing organs.
These legs are usually held inside the carapace, in the cavity containing the breathing organs.
It is sometimes called the robber crab or palm thief (in German, Palmendieb), because some coconut crabs are rumored to steal shiny items such as pots and silverware from houses and tents.
Another name is the terrestrial hermit crab, due to the use of shells by the young animals (although terrestrial hermit crab also applies to a number of other hermit crabs — see Australian land hermit crab).
However, while these gills were probably used to breathe under water in the evolutionary history of the species, they no longer provide sufficient oxygen, and an immersed coconut crab will drown within a few hours or minutes (reports vary, probably depending on the levels of stress and exercise and the resulting oxygen consumption).