Ingo Arndt / Blue Crab (Discoplax hirtipes) in defensive posture, Christmas Island, Indian Ocean, Territory of Australia

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.

Stephen Belcher / Christmas Island Red Crab (Gecarcoidea natalis) and Blue Crab (Discoplax hirtipes) carcasses, death caused by Yellow Crazy Ants (Anoplolepis gracilipes), Christmas Island National Park, Christmas Isla...

Stephen Belcher / Christmas Island Red Crab (Gecarcoidea natalis) and Blue Crab (Discoplax hirtipes) carcasses, death caused by Yellow Crazy Ants (Anoplolepis gracilipes), Christmas Island National Park, Christmas Isla...

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.

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

Juergen Freund / Radio transmitter on blue marked Christmas Island red crab {Gecarcoidea natalis}. Christmas Is, Indian Ocean

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

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

Stephen Belcher / Blue Crab (Discoplax hirtipes) carcass, death caused by Yellow Crazy Ants (Anoplolepis gracilipes), Christmas Island National Park, Christmas Island, Australia

Sue Flood / Coconut crab / Robber crab pair {Birgus latro} Christmas Is, Indian Ocean