They fly over Lake Superior without resting; in fact, observers there have discovered a curious thing. Instead of flying directly south, the monarchs crossing high over the water take an inexplicable turn towards the east. Then when they reach an invisible point, they all veer south again. Each successive swarm repeats this mysterious dogleg movement, year after year. Entomologists actually think that the butterflies might be “remembering” the position of a long-gone, looming glacier.
