Prompted, perhaps, by overcrowding in its home in the Yucatan, a cloudless sulphur butterfly journeys through the rainforest, over the Gulf of Mexico and across a helpful map of the U.S., passing ponies on Assateague Island and sheltering from a storm in New York’s Central Park, before arriving in southern Vermont, where it will mate and die. Its offspring are shown hatching on a cassia plant in the garden where they will spend their lives. The careful reader of the backmatter will realize that this is a one-way journey; unlike the monarch, these butterflies do not fly south, but this is not stated directly in the text. Realistic watercolor illustrations cross page boundaries and details escape into the margins and the area reserved for the evocative text, an imitation of the butterflies’ action as they erupt from their normal habitat and spread northward. Young readers will come away with a sense of wonder and admiration for the frail creature’s remarkable flight. (author’s note) (Picture book/nonfiction. 5-9)