This riddle doesn't include any question! The tale is nice, but what's the problem?
The only thing I can do is guess that you want to hear what the tale means:
There were exactly 40 married couples in Mamajorca. Each night since the proclamation, every man slept with another woman than his own, and with another than any of the nights before. On the 40th night, they all came home to sleep with their own wives and were exterminated, thereby dooming the future of Mamajorca, because there would be no more offspring!
OK ... I guess I have to amend my attitude ... so I will assume that users of my forum can not always find implied questions and they have to be led like little children ... I have moved the questions to the wording of the puzzle