The planktonic larva of the worm settles on a suitable crab host and encysts on the exoskeleton.

After mating, the mature female crab stores the sperm for several months, before releasing a batch of fertilised eggs onto her abdomen, where she tucks them under the tail flap.

At this stage, the ribbon worm migrates to the mass of eggs and feeds on the developing embryos.

[4] It has been found that the worm is adversely affected by a lowering of the water salinity.

[6] In 1980, the central California fishery was badly affected; Carcinonemertes errans was implicated, with 50% of the crabs' eggs produced each year being predated.