Pete Oxford / Blue Land Crab (Cardisoma guanhumi) male, Banco Chinchorro, Yucatan Peninsula, Mexico

Piotr Naskrecki / Brown Land Crab (Cardisoma carnifex), Vamizi Island, Mozambiqiue

Luis Quinta / White forest crab (Cardisoma armatum) Island of Principe UNESCO Biosphere Reserve, Democratic Republic of Sao Tome and Principe, Gulf of Guinea.

Luis Quinta / White forest crab (Cardisoma armatum) portrait, seen through claw, Island of Principe UNESCO Biosphere Reserve, Democratic Republic of Sao Tome and Principe, Gulf of Guinea.

Luis Quinta / White forest crab (Cardisoma armatum) Island of Principe UNESCO Biosphere Reserve, Democratic Republic of Sao Tome and Principe, Gulf of Guinea.

Martin Gabriel / Mangrove crab (Cardisoma carnifex) , Curieuse Island, Republic of Seychelles

Roland Seitre / Red Claw Crab (Cardisoma carnifex) Gossanah, Ouvea, Loyalty Islands Province, New Caledonia.

Claudio Contreras / Blue Land Crab (Cardisoma guanhumi), Sian Ka'an Biosphere Reserve, Yucatan Peninsula, Mexico, August.

Claudio Contreras / Blue Land Crab (Cardisoma guanhumi), Sian Ka'an Biosphere Reserve, Yucatan Peninsula, Mexico, August.

Charlie Summers / Cocos Purple Land Crab (Cardisoma carnifex) in defensive position. Cocos-Keeling Island, Indian Ocean, Australia, May.

Brent Stephenson / Blue Land Crab (Cardisoma carnifex) walking over coral rubble on land. Mataiva, Tuamotus, French Polynesia, October.

Pete Oxford / Blue Land Crab (Cardisoma sp). Sian Ka'an, Biosphere Reserve, Quintana Roo, Yucatan Peninsula, Mexico.

Pete Oxford / Blue Land Crab (Cardisoma sp). Sian Ka'an, Biosphere Reserve, Quintana Roo, Yucatan Peninsula, Mexico.

Pete Oxford / Giant Land Crab (Cardisoma guanhumi) branding a claw. Mahahual Penninsula, South Yucatan Peninsula, Mexico, October.

Pete Oxford / Portrait of a Giant Land Crab (Cardisoma guanhumi). Mahahual Penninsula, South Yucatan Peninsula, Mexico, October.

Charlie Summers / Cocos-Keeling / Blue Land Crab (Cardisoma carnifex) on beach, North Keeling, Cocos-Keeling Island Group, Australia.

Juergen Freund / Blue land crab {Cardisoma carnifex} on rocks on shore, Camarines Sur, Luzon, Philippines

Albert Lleal / Blue Land Crab (Cardisoma guanhumi) in defensive posture, Juventud Island, Cuba

Rod Williams / Giant land crab {Cardisoma guanhumi} beside tree trunk. Captive, occurrs in West Africa and West Indies

Piotr Naskrecki / Blue Land Crab (Cardisoma guanhumi) female, cautiously approaching the edge of the beach to release her eggs during full moon, Dominican Republic

Piotr Naskrecki / Blue Land Crab (Cardisoma guanhumi) male, sporting giant claws used in territorial combat, Dominican Republic

Rod Williams / Giant land crab {Cardisoma guanhumi} captive, from West Indies and West Africa

Pete Oxford / Blue mangrove crab {Cardisoma crassum} Machililla NP, Ecuador

Pete Oxford / Blue mangrove crab {Cardisoma crassum} Machililla NP, Ecuador

Pete Oxford / Blue mangrove crab {Cardisoma crassum} Machililla NP, Ecuador

Claudio Velasquez / Blue land crab {Cardisoma carnifex} Madagascar

Gary Bell/ Oceanwide / Brown Land Crab (Cardisoma carnifex) in defensive posture, Keeling Islands, Australia

Gary Bell/ Oceanwide / Brown Land Crab (Cardisoma carnifex), Keeling Islands, Australia

Pete Oxford / Blue Land Crab (Cardisoma guanhumi) male, Banco Chinchorro, Yucatan Peninsula, Mexico

Pete Oxford / Blue Land Crab (Cardisoma guanhumi) male, Banco Chinchorro, Yucatan Peninsula, Mexico

Joel Sartore / Photo Ark / Blue land crab (Cardisoma guanhumi) portrait, near Vero Beach, Florida, USA.

Joel Sartore / Photo Ark / Blue land crab (Cardisoma guanhumi) portrait, near Vero Beach, Florida, USA.

Emanuele Biggi / Giant land crab (Cardisoma carnifex) raising its big pincer in defensive posture, Praslin island, Seychelles.

Emanuele Biggi / Giant land crab (Cardisoma carnifex) feeding on fallen leaf in coastal forest at night, Praslin island, Seychelles.

Joel Sartore / Photo Ark / African rainbow crab (Cardisoma armatum) walking sideways into frame, Petra Aqua. Captive.

David Fleetham / Brown land crab / Chestnut crab (Cardisoma carnifex) on pile of branches, Fiji.

Staffan Widstrand / Wild Wonders of China / Taiwan's largest land crab species (Cardisoma carnifex) Banana Bay Forest Rerserve, Kenting National Park, Taiwan

Francisco Marquez / Giant land crab (Cardisoma) Islas Marias Archipelago, Marias Biosphere Reserve, Mexico.

Francisco Marquez / Giant land crab (Cardisoma) hiding in vegetation. Islas Marias Archipelago, Marias Biosphere Reserve, Mexico.

Francisco Marquez / Giant land crab (Cardisoma) hiding in vegetation. Islas Marias Archipelago, Marias Biosphere Reserve, Mexico.