Common Box Crab

This box crab spends its days buried in the sand with only its eyes showing, then comes out at night to crush open shells for a meal.

Also known as: reef box crab, smooth box crab

Buried in sand with only its eyes showing, it is easy to mistake for a shell or a pebble. Look for the flared, tooth-edged rear shell that hides its legs, unlike an open-legged reef crab.

Its shell is mottled greyish-brown and covered in small bumps, which helps it blend into sand when half-buried. The rear of the shell flares out into broad, blunt-toothed extensions that hide its walking legs from view. Its two claws are uneven in size and shape, built for cracking open shells rather than for speed.

It lives on sandy or shelly seabeds, often in reefs and seagrass meadows, across the tropical Indo-Pacific from the Red Sea to the Pacific islands, down to about 150 m.