If the way of maintaning a single queen is done as Rettick sugestst then there is jet another posibilety to why mollock would want to kil his mother. Since all glucks would then again become fertile he could start his own empire by schoosing a mate. He could consipire with a to be female who's interested in becoming a queen.
And then as soon as the current queen is out of the way start a new empire and take over befour anyone else has to cance to rise to the top.