The crabs will mate during the moulting stage. The crabs will engage in a pre-mating embrace where the male individual places his claws and thighs around the female. This embrace may last for several days, after which the female crab will begin to shed her hair and the pair will begin mating. The male crab passes his sperm to the female by inserting his reproductive limbs (tentacle-like reproductive organs) into the two reproductive holes underneath the female, also known as germinal (bud) bodies. The female crab stores the sperm in a storage sac called the fertilization sac until she is ready to start using it.
Some crabs will mate standing upright facing each other, but most species choose the missionary position (which refers to the male-on-top-female sexual position). Once copulation is complete, the male crab guards the female for a period of time (giving her long enough for her shell to harden) and then leaves in search of the next new mate.