it seem extraordinary that during the latter half of the twentieth century when we were exploring space and men were walking on the moon, the outside world knew nothing of this wonderful spectacle. it was not discovered untill 1975 and then thankfully immediately protected. But there is still a lot we don't know about the way which these butterflies behave, but one thing is certain the trigger that sends them on these extraordinary journeys are the seasonal changes that are brought about by the way our planet, the earth, rotates about the sun