Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) crossing closed road, during annual migration, Christmas Island, Indian Ocean, Australian Territory, November 2009.

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) crossing road in huge numbers during annual migration, Christmas Island, Indian Ocean, Australian Territory

Franco Banfi / Portunid crab (Liocarcinus depurator) scuttling across the seabed, Trondheimfjord, Norway, North Atlantic Ocean.

Bruce Thomson / Orange-clawed fiddler crab (Uca coarctata), brilliant orange form, scuttling across beach, Broome, Western Australia.