I, Arthus, have made a theory on how and why pigmen disappear in daylight. The reason is that since they live in the Nether, they are weakend by the sunlight so they had to find a way to escape before the sun killed them. The undead cracked a deal with the beasts. They were still alowed to attack at will but if they gave minas from each kill to the undead the undead in turn, would trasport them form the Neather to the Land of Ageis depending on the time of day. So that is my theory of the Pigmens abillity to teleport in the day. The End.