Africanized bee
In 1956, scientists brought African and European bees to Brazil, to see if they could mate them.  They wanted to do this to make a bee that would make more honey in a hotter place.  Scientists called these new bees "Africanized honeybees".  These bees, however, were very different from regular honeybees.  They would suddenly leave the colony and build a hive somewhere else.  Scientists found out that the queen would decide to leave after a few months, usually taking half the colony with her.  They could even take over European hives by killing the European queen bee and making their own queen bee the "queen".