In late winter and spring as coastal water temperatures rise, female rock lobsters shed their shells and develop into breeding condition. Before they lay eggs there are signs that they are preparing to spawn.

One sign is the growth of long fine hair-like filaments, or setae, underneath their tails. The 'hair' grows on the inner forked structures (endopodites) which form part of their swimmerets. Females with these hairs are termed 'setose'.

After spawning, the eggs stick to these 'hairs' and allow 'berried' females to carry the eggs under their tails.

A second sign that female lobsters are ready to spawn is a 'tar spot' on the underside of the carapace between their hindmost pair of legs.

This black (or sometimes grey) putty-like spot is a packet of sperm attached to the female by the male during mating.

During spawning the female releases sperm from the tar spot to fertilize the eggs by gradually scratching the outer coating away with a specialised claw on her hindmost pair of legs.

Female lobsters in spawning condition usually have both 'hair' (setae) and tar spots, but some just prior to mating may have only setae