These are when an Ant kills a Spore. It has only happened 5 times before, and always by Gregor the Ultimate Ant.
Miranda was the well known and popular wife of Harry I. Four years after his death, in her old age, she went out for a walk to try and target the weak ant burrow. On her way, however, she was ambushed by Gregor and the previously great fighter was not up to the standard of Gregor in hr old age.
Aldin was never very good at Ant Infecting. When faced with the monstrocety that is Gregor, he fled. But lack of speed led to him be captured and killed by Gregor.