John Shaw / Sally lightfoot crabs (Grapsus grapsus) on the beach at Puerto Egas, Santiago Island, Galapagos, May.

Cyril Ruoso / Short-tailed Crab (Potamocarcinus richmondi) in defensive posture, Barro Colorado Island, Panama

Christian Ziegler / Short-tailed Crab (Potamocarcinus sp) in defensive posture, Barro Colorado Island, Panama

James Christensen / Short-tailed Crab (Pseudothelphusidae) in defensive posture on forest floor, Mindo, western slope of Andes, Ecuador

Piotr Naskrecki / Short-tailed Crab (Fredius sp) can often be found outside of water, foraging on the forest floor, Guyana

Joel Sartore / Photo Ark / Forest crab (Pseudothelphusidae sp) looking at the camera and moving its legs, Tapir Valley Nature Reserve, Costa Rica. Controlled Conditions.