The Monarch butterfly (Danaus plexippus) is a milkweed butterfly (subfamily Danainae), in the family Nymphalidae. It is perhaps the best known of all North American butterflies. Its wings feature an easily recognizable orange and black pattern, with a wingspan of 8.9–10.2 centimetres (3½–4 in). (The Viceroy butterfly has a similar size, color, and pattern, but can be distinguished by an extra black stripe across the hind wing.) Female Monarchs have darker veins on their wings, and the males have a spot called the "androconium" in the center of each hind wing from which pheromones are released. Males are also slightly larger.
The Monarch is famous for its southward migration and northward return in summer in the Americas which spans the life of three to four generations of the butterfly.