A very common land crab in the coastal lowland tropical rain forests of Costa Rica is the Halloween Crab (Gecarcinus quadratus). Halloween Crabs have several common names and are also known as Mouthless Crabs or Harlequin Land Crabs.
Halloween Crabs are quite attractive with a black carapace, orange legs, and purple claws. Because they are terrestrial and so colorful, Halloween Crabs are sold as exotic terrarium pets. In the wild, these nocturnal land crabs live in small burrows in the coastal jungles of Costa Rica. Although they are terrestrial, Halloween Crabs are most common near the coast because they must return to the ocean in order to reproduce. They range from the coast to about 0.4 miles (600 m) inland.
Halloween Crabs emerge at night to collect fallen leaves and seedlings, which they then drag back into their burrows to eat in safety. These terrestrial land crabs can also be seen climbing trees with ease during their nighttime foraging. During the day, these colorful crabs hide in underground burrows.
Halloween Crabs are the most active during the rainy season in Costa Rica, and I saw quite a few them crawling around every night during my May of 2006 trip to Costa Rica.