Commission from   Lyndane for   Phantasie

Parasites don't naturally try to latch on to already infected hosts. Not only would this be a waste of resources, Parasites of the same kind usually can't. Succubats latch on at the base of the back, crown crabs latch onto the head. If a parasite is already there, then the spot's taken.

Sometimes a hive who has lost their queen will choose someone from the hive to be the new queen though, forcing the new merger. They might also put crown crabs onto succubat criminals who are too disruptive or violent for society, hosts who would otherwise get punished otherwise. Since hive culture varies from hive to hive, this could be never, or a substitute for the death penalty.