Gecarcinus is the type genus

Type genus

In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...

 of the land crab

Land crab

Gecarcinidae is a family of true crabs that are adapted for terrestrial existence, commonly known as land crabs. Similar to all other crabs, land crabs possess a series of gills. In addition, the part of the carapace covering the gills is inflated and equipped with blood vessels. These organs...

 family Gecarcinidae. They are found in warmer coastal regions of the Americas

Americas

The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

, including islands in the Caribbean

Caribbean Sea

The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....

. Four species from oceanic islands were formerly included in Gecarcinus as the subgenus Johngarthia, but are now treated as a separate genus, Johngarthia

Johngarthia

Johngarthia is a genus of crabs in the land crab family Gecarcinidae, formerly included in the genus Gecarcinus, and containing the following five species:...

. While all members of this genus are largely terrestrial

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

, they have to return to the ocean to breed (the larvae

Crustacean larvae

Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow...

 are released into the sea). They are often colourful, with reddish, orange, purple, yellowish, whitish or blackish being the dominating hues. This has resulted in some species, notably G. quadratus and G. lateralis, gaining a level of popularity in the pet-trade.

Species

Three species are now included in the genus Gecarcinus:

• Gecarcinus lateralis
  Gecarcinus lateralis
  Gecarcinus lateralis, also known by the common names blackback land crab, Bermuda land crab, red land crab and moon crab Gecarcinus lateralis, also known by the common names blackback land crab, Bermuda land crab, red land crab (leading to easy confusion with Gecarcoidea natalis) and moon crab...
  
  (Fréminville, 1835)
• Gecarcinus quadratus Saussure, 1853
• Gecarcinus ruricola
  Gecarcinus ruricola
  Gecarcinus ruricola is a species of terrestrial crab. It is the most terrestrial of the Caribbean land crabs, and is found from western Cuba across the Antilles as far east as Barbados. Common names for G...
  
  (Linnaeus, 1758)

Further reading

• Bright, D., & C. Hogue. 1972. A synopsis of burrowing land crabs of the World and list of their arthropod symbionts and burrow associates. Contributions in Science. No. 220. Available online (PDF)
• Ng, P., & D. Guinot, 2001. On the land crabs of the genus Discoplax A. Milne Edwards, 1867 (Crustacea: Decapoda: Brachyura: Gecarcinidae), with description of a new cavernicolous species from the Philippines. Raffles Bull. Zool. 49: 311-338.
• Türkay, M. 1970. Die Gercarcinidae Amerikas. Mit einem Anhang uber Ucides Rathbun (Crustacea: Decapoda). Senckenberg. biol. 51: 333-354.
• Türkay, M. 1987. Landkrabben. Natur Mus. 117: 143-150.