The female Pachygrapsus carries the fertilized eggs under her abdomen that are stuck via hairs to her pleopods.  The eggs can develop for a few months before hatching, out of which come zoea larvae.  The carapace of typical brachyuran zoea is spherical, bearing a ventrally pointing rostrum, a dorsal spine, and a lateral spine on either side.  The larva more resembles a shrimp than a crab in these early stages.  

As zoea, the larvae float offshore and live within the plankton, feeding on metazoa, other larval forms, and smaller protozoa.  The zoea appear narrow and shrimplike, and swim using appendages of the cephalothorax that eventually turn into the mandibles and antennae of the adult crab.