Halloween Moon Crab

Gecarcinus quadratus

The Halloween moon crab, Gecarcinus quadratus, is a colorful land crab from Pacific coastal forests and beaches of Central America, with records extending into nearby tropical coastlines. It is also sold as the Halloween crab, moon crab, or harlequin land crab. The usual pet-trade animal has orange legs, a dark purple to blue-black carapace, pale patches near the eyes, and a reddish or orange underside. Adults spend most of their lives on land in humid burrows, but like many land crabs they return to the sea to release larvae, so captive breeding is rarely achieved.

Keeping this crab is closer to maintaining a humid terrarium than a fish tank. It needs deep moist substrate for burrowing, a warm sealed enclosure with ventilation, and both fresh water and marine-salt water dishes it can enter and leave safely. Leaf litter, vegetables, fruit, calcium sources, and small amounts of animal protein match its scavenging diet better than a single prepared food. Halloween moon crabs can be defensive and may injure one another in cramped quarters, especially around molts. Most animals in trade are wild caught, so buyers should look for active crabs with intact limbs and plan for minimal handling.