This listing is for 50 Frogs Pane of 20 Forever postage stamps. Numbering more than 4,000 species, frogs live on every continent except Antarctica. Of those thousands, more than 90 species are found in the United States. Digital illustrations of four North American frogs grace these new stamps: the Pacific tree frog, the northern leopard frog, the American green tree frog, and the squirrel tree frog. Working with a primarily green color palette, the artist captured the essence of each animal with enough important defining features to make each recognizable.