Costa Rica’s alligator bug, Fulgora laternaria, bears a protuberance that looks remarkably like a caiman’s head — a feature that may make a hungry bird think twice. The leaf insects of Southeast Asia, below, so convincingly mimic living leaves that they even bear “bite marks.” This fooled Magellan’s companion Antonio Pigafetta, who encountered them in the Philippines in 1521: In this island are also found certain trees, the leaves of which, when they fall, are animated, and walk. They are like the leaves of the mulberry tree, but not so long; they have the leaf stalk short and pointed, and...