CarapaceThe hard shell that covers the head and body from above. A crab's is wide and flat.
EyesThe two compound eyes at the front of the shell. Each sits on the end of a stalk.
EyestalksThe short movable stalks that hold the eyes up. A crab can fold them down into sockets in the shell.
AntennaeThe feelers at the front, between the eyes. Crabs have a second, smaller pair, the antennules, beside them.
ClawsThe first pair of legs, each ending in a pincer. Used for catching food and fighting. Their proper name is chelipeds.
Walking legsThe four pairs of legs behind the claws. A crab walks on them, often sideways.
MouthpartsFlat plates that close over the mouth like a pair of doors. They are on the underside and are the outer foot-jaws, or maxillipeds.
AbdomenThe crab's tail, folded tight under the body. It is often called the apron: narrow in a male, broad and round in a female, who carries her eggs under it.
How this list was compiled: Read 2026-09-27. (1) Wikipedia, Crab, https://en.wikipedia.org/wiki/Crab : crabs are decapods (ten legs), the first pair being chelipeds; the abdomen is short and folded under the thorax; a thick exoskeleton. (2) Wikipedia, Decapod anatomy, https://en.wikipedia.org/wiki/Decapod_anatomy : carapace, stalked compound eyes, antennae and antennules, maxillipeds, pereiopods, pleon (abdomen) with pleopods for carrying eggs in females. (3) Wikipedia, Blue crab, https://en.wikipedia.org/wiki/Callinectes_sapidus : the abdomen called the apron, its shape telling males from females. (4) Encyclopaedia Britannica, 11th edition (1911), Crab, via Wikisource: the abdomen small and folded under the body, narrow and triangular in the male, broad in the female, which carries the eggs; five pairs of legs, the first with nippers (chelae); eyes on movable stalks that fold into sockets; the eyes can be withdrawn into sockets in the front of the carapace; the broad, flat third pair of foot-jaws covers the opening round the mouth. Licence: own work
The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work
How it works
These are the parts of a crab on one crab drawn twice: from above, then turned over. Five parts show from the top, and the mouthparts and abdomen only from underneath.
Read the full guide
From above
The wide shell over the back is the carapace. At the front, two eyes sit on short stalks with the antennae between them. The first pair of legs are the claws; behind them come four pairs of walking legs.
Underneath
Turn the crab over. At the front, two flat plates cover the mouth. Down the middle, the abdomen lies folded flat against the body. A crab's tail is this small flap, not a long tail like a lobster's.
Count the legs on the drawing: five on each side, claws included, makes the ten that give crabs the name decapod.
Questions and answers
How many legs does a crab have?
Ten, in five pairs. The first pair are the claws and the other four pairs are walking legs. That is why crabs belong to the decapods, which means ten-footed.
How can you tell a male crab from a female?
Turn it over and look at the abdomen, often called the apron. A male's is narrow, a female's is broad and rounded, and she carries her eggs under it.
What is a crab's shell called?
The hard shell over the back is the carapace. It is part of the crab's exoskeleton, the hard outer skin that covers the whole body and legs.