Folds its claws flat across the front like shutters and spends the day buried in sand.
A box crab with a carapace to about 10 cm across, cream to pale yellow and marked with purple-brown spots and streaks, with a large dark red-brown ring around each orbit that gives the species its usual identification. The rear corners of the carapace are drawn out into flat plates that roof over the walking legs, and the claws are deep, flattened and shaped so that when folded they close the whole front of the animal, leaving a smooth box with nothing exposed. Calappa calappa is much larger, smoother and more uniformly reddish or purplish without the orbital rings; Calappa hepatica is smaller, heavily warted and mottled brown. The genus as a whole is unmistakable once the folded-claw posture is seen.
Spends the day buried in sand with only the eyes and the front edge of the carapace clear, and emerges at night to hunt gastropods and hermit crabs. The right claw carries a stout tooth at the base of the fixed finger which the crab uses as a tin-opener, gripping the lip of a snail shell and chipping progressively round the whorl until the occupant is exposed; the left claw holds the shell steady. Recorded from about 5 to 50 m. Buried animals show as a shallow oval outline with two eyes at one end, and the crab will usually stay put and rely on the disguise rather than run, so it can be watched for as long as the sediment around it is left undisturbed.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
