Hello Michael, The pattern you are referring to is known as the butterfly pattern. This pattern coincides with the 11 year solar activity cycle. So not only do the number of sunspots change but their locations do as well. They migrate from about 35 degrees north and south latitude towards the equator. Since we are approaching the end of our cycle, the sunspots are currently appearing closer to the equator. The reason for this migration is not clearly understood. Here is an article from national geographic that discusses this http://news.nationalgeogr...050205_sunspots.html