Monarch butterfly

Commonly and easily mistaken for the similar viceroy butterfly, the monarch’s wingspan ranges from 8.9 to 10.2 centimeters (3.5–4.0 in). The uppersides of the wings are tawny-orange, the veins and margins are black, and in the margins are two series of small white spots. Monarch forewings also have a few orange spots near their tips. Wing undersides are similar, but the tips of forewings and hindwings are yellow-brown instead of tawny-orange and the white spots are larger. The shape and color of the wings change at the beginning of the migration and appear redder and more elongated than later migrants. Wings size and shape differ between migratory and non-migratory monarchs. Monarchs from eastern North America have larger and more angular forewings than those in the western population.

Adults exhibit sexual dimorphism. Males are slightly larger than females and have a black patch or spot of androconial scales on each hindwing (in some butterflies, these patches disperse pheromones, but are not known to do so in monarchs). The male's black veins on his wings are lighter and narrower than those of females. (information from Wikipedia)