I always introduce them by holding the male outside the female's cage so they can see each other but not attack each other. If the female remains calm and does not gape, hiss, rock back and forth, darken her colors and the male does not act aggressively then the male may be placed in he females cage...but continue to watch them until you are sure they aren't going to fight. I leave them together as long as they aren't aggressive until the female starts to reject the male....as long as the male behaves too.