The Monarch Rex, or Danaus Plexippus trans., is the ultimate symbol of the survival of life in the face of impossible odds. When the Invasion first began, the Monarch Butterfly was finnishing up it's winter in Mexico and was begining to return to it's summer home in North America, only to run into the reality storms surrounding the Eastern Living Land. Only half the population of Monarchs returned to Mexico the first winter post-Invasion. With the expansion of the Western Lands, this number dropped dramatically the next year, and the Monarch was thought to have been wiped out as a species.
And then a miracle occured. The third winter post-invasion, natives, tourists, and entymologists were are surpised to once again see the small Mexican forest once again carpeted in orange and black. But it was not the Monarch they knew - only a few thousand returned, and yet the entire valley was filled just as surely as it had three years before by billions! A quick thinking - and even faster running - young entymologist dubbed the new species "Monarch Rex", and the name stuck. The news of the Giant Butterflies spread, bring even more tourists and entymologists to the area.
With the arrival of the Akashans in the middle of the War, it was conclusively determined that the Monarch Rex was in fact the old Monarch Butterfly, and not an alien species. While the reality storms around the Living Land had destroyed most of the population, it had not gotten all of them. The survivors found the realm a harsh but ultimately rich habitat, and they grew to tremendous size. Their numbers continued to dwindle however, as the migration instinct continually took them through reality storms and out into a world that could no longer support their existance. Enough gave up on migration and remained within the confines of their new reality to form a stable population. But a select few still "remember the old ways", and can be found in any of the Monarch's original habitats. Some have even started to range further and further, in search of sufficient neutrients to support their larger bodies. At least one Monarch Rex has made it as far as South America, and unconfirmed reports of "Giant Moths" have come in from the Pacific Islands.