Ingo Arndt / Blue Crab (Discoplax hirtipes) with claws raised in defensive / aggressive posture, endemic to Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Blue Crab (Discoplax hirtipes) with claws raised in defensive / aggressive posture, endemic to Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) blurred view of vast number of individuals moving along their annual migration route, Christmas Island, Indian Ocean, Australian Territory

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

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) arriving in huge numbers, at coast for spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) gatthered together on beach the day before spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) massing on coastal rocks, the morning after spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) shortly before sunrise sitting on rock ready for spawning, Christmas Island, Indian Ocean, Australian Territory

Juergen Freund / Land Hermit crab using a plastic bottle cap as its home. Kavieng, Papua New Guinea, June 2010

Kim Taylor / Land hermit crab (Coenobita species) captive, Southern Madagascar

Juergen Freund / Thousands of Christmas Island Red crabs on rocky shore (Gecarcoidea natalis)

Juergen Freund / Christmas Island red crab (Gecarcoidea natalis) wearing Father Christmas hat, Christmas Island, Indian Ocean

Jean E. Roche / Land crab burrowing in sand on beach {Ocypode quadrata} Guadeloupe 2000.

David Fleetham / Land crab (Gecarcinidae) pausing just above high tide mark, Savusavu, Fiji.

Staffan Widstrand / Land crab, rainforest, Batenta Island, Raja Ampat, Western Papua, Indonesia.

Ingo Arndt / Group of Christmas Island red crabs (Gecarcoidea natalis) walking during migration, Christmas Island, Indian Ocean, Australian Territory, December

Ingo Arndt / Christmas Island red crabs (Gecarcoidea natalis) gathered on coastal rocks during spawning, Christmas Island, Indian Ocean, Australian Territory, November

Ingo Arndt / Christmas Island red crabs (Gecarcoidea natalis) gathered on coastal rocks during spawning, Christmas Island, Indian Ocean, Australian Territory, November

Ingo Arndt / Christmas Island red crab (Gecarcoidea natalis) migrating, Christmas Island, Indian Ocean, Australian Territory, November

Ingo Arndt / Christmas Island red crabs (Gecarcoidea natalis) migrating across road, Christmas Island, Indian Ocean, Australian Territory, November

Ingo Arndt / Two Christmas Island Red Crabs (Gecarcoidea natalis) locked in combat, on rocks, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) feeding on the remains of another crab crushed on the road, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Wildlife Photographer Ingo Arndt taking pictures of Christmas Island Red Crabs (Gecarcoidea natalis) in coastal cavern, Christmas Island, Indian Ocean, Australian Territory, November 2009.

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis)female spawning in shallow water near beach, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) mass arrived on coast for spawning / Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) / crushed by car while crossing the road during annual migration, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) / sitting on road during annual migration, eating fruit, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) dirty after walking through a phosphate mining area crossing road during annual migration, Christmas Island, Indian Ocean, Australian Territory

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

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) close-up of claw, Christmas Island, Indian Ocean, Australian Territory.

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) eggs in females opened brood pouch shortly before spawning / Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) female with eggs shortly before spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) female carrying eggs on migration, shortly before spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) migrating female carrying eggs on sandy beach, shortly before spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) arrived at coast for spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) arrived at coast for spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) arrived at coast for spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) arriving in huge numbers, at coast for spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) arriving in huge numbers, at coast for spawning, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) females spawning in shallow water near beach, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) portrait of individual feeding on green vegetation, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) close-up of head, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) portrait standing on white surface, Christmas Island, Indian Ocean, Australian Territory.

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) male awaits females at entrance to mating burrow, Christmas Island, Indian Ocean, Australian Territory

Konrad Wothe / Land crab in defensive postur rainforest, . Gilpin trail, Tobago, West Indies, Caribbean.

Kerstin Hinze / Land Crab (Neosarmatium africanum) portrait. St Lucia, Indian Ocean coast, eastern South Africa.

Kerstin Hinze / Land Crab (Neosarmatium africanum) portrait. St Lucia, Indian Ocean coast, eastern South Africa.

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.

Yukihiro Fukuda / Christmas Island Crab covered in salt, found in the salt fields.

Claudio Contreras / Land Hermit Crab (Coenobita compressus) in nerita snail (Nerita sp.) shell, Maria Cleofas Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, August.

John Cancalosi / Haloween / Red Land Crab (Gecarcinus quadratus). Costa Rican tropical rainforest.

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

Ernie Janes / Crab pots and crabbing boat on beach, Southwold, Suffolk, UK, May

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

Brent Stephenson / Strawberry Hermit Crab (Coenobita perlatus) walking over coral rubble. Takutea, Cook Islands, November.

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.

Juergen Freund / Thousands of newly hatched baby Land crabs emerging from the sea where they lived as planktonic larvae and are now ready to go back to the forest for their adult lives. Bird's Head Peninsula, West Pap...

Daniel Heuclin / Portrait of a Land Ghost Crab (Ocypoda quadrata). French Guyana, October.

Charlie Summers / Christmas Island Red Land Crab (Gecarcoidea natalis) on coastal rocks, Christmas Island, Indian Ocean, Australia.

Charlie Summers / Robber /Coconut Crab (Birgus latro) stripping a coconut of the outer shell, constantly guarding its work from other crabs. Chirstmas Island in the Indian Ocean. This is the worlds largest living land...

Charlie Summers / Christmas Island Red Land Crab (Gecarcoidea natalis) in shallow water, Christmas Island, Indian Ocean, Australia

Charlie Summers / Three male Christmas Island Red Crabs (Gecarcoidea natalis) huddled together in a safe hole in rocks on a beach, await the arrival of the female Red Crabs as their part of the annual migration. Chris...

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

Charlie Summers / Strawberry land Hermit Crab (Coenobita perlatus) moving across beach, in early morning. Cocos-Keeling Island group of Australia.

Edwin Giesbers / Land crab (Gecarcinidae) on moss in tropical forest, Sarawak Borneo, Malaysia,

Edwin Giesbers / Land hermit crab (Coenobita rugosus) in spiral seashell on beach, Bako National Park, Sarawak, Borneo, Malaysia

Alex Hyde / Forest Crab on plant leaf at night in rainforest, Masoala Peninsula National Park, north east Madagascar.

Charlie Summers / Red Land Crabs (Gecarcoidea natalis) crawling over roots of tree, on their migration pathway from the forests to coast, Christmas Island, South East Asia

Charlie Summers / Red Land Crabs (Gecarcoidea natalis) crossing suburban road on migration, Christmas Island, South East Asia

Gary K. Smith / Traditional Cromer crab boats with tractors on beach, with pier in background, UK, October 2009

Mark Bowler / Purple pincher / Purple claw land hermit crab {Coenobita clypeatus} investigating a new shell, a tropical rainforest land crab from the Caribbean.

Mark Bowler / Purple pincher / Purple claw land hermit crab {Coenobita clypeatus} a tropical rainforest land crab from the Caribbean. Sequence showing crab emerging from shell. Digital composite

Mark Bowler / Purple pincher / Purple claw land hermit crab {Coenobita clypeatus} a tropical rainforest land crab from the Caribbean. Sequence showing crab emerging from shell. Digital composite

Mark Bowler / Purple pincher / Purple claw land hermit crab {Coenobita clypeatus} a tropical rainforest land crab from the Caribbean. Sequence showing crab emerging from shell. Digital composite

Mark Bowler / Land hermit crab (Coenobita clypeatus)

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

Tim Laman / Visayan tarictic hornbill (Penelopides panini) male holding a land crab in its beak for delivery to the female and chicks in the nearby nest, Northwest Panay Island Natural Park, Philippines. Endanger...

Edwin Giesbers / Red / Halloween land crab (Gecarcinus quadratus), Costa Rica

Edwin Giesbers / Red / Halloween land crab (Gecarcinus Quadratus), Costa Rica

Inaki Relanzon / Land hermit crab {Coenobitoidea} walking across sand, Nosy Tanikeli, near Nosy Be, North Madagascar,

Jouan & Rius / Red / Halloween land crab (Gecarcinus quadratus) in mangrove, pacific coast, Costa Rica

Jouan & Rius / Small land crab on eroded linestone 'tsingy' rock formations during rainy season, Ankarana NP, Madagascar

Tim Laman / Unidentified land crab from Panay Island Northwest mountains, Philippines. May

Juergen Freund / Man sweeping up some baby Christmas Island red crabs {Gecarcoidea natalis} as they cross a street in Kampong village, Christmas Island

Juergen Freund / Christmas Island red crab {Gecarcoidea natalis} eating eggs from another crab. Christmas Is, Indian Ocean

Juergen Freund / Christmas Island red crab {Gecarcoidea natalis} wearing Father Christmas hat, Christmas Is, Indian Ocean

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

Steven David Miller / Land hermit crab {Isocheles pilosus}, Lady Elliott Island, Great Barrier Reef, Queensland, Australia

Juergen Freund / Scientist examines Christmas Island red crab {Gecarcoidea natalis} Christmas Is, Indian Ocean

Juergen Freund / Christmas Island red crab {Gecarcoidea natalis} with cracked shell, Christmas Is, Indian Ocean

Juergen Freund / Scientist examines leg removed from Christmas Island red crab {Gecarcoidea natalis} Christmas Island, Indian Ocean