Commonly and easily mistaken for the similar viceroy butterfly, the monarch's wingspan ranges from 8.9 to 10.2 centimetres (3.5–4.0 in). The uppersides of the wings are tawny orange, the veins and margins are black, and there are two series of small white spots in the margins. 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. Monarch flight has been described as "slow and sailing". Monarch flight speed has been estimated by a number of researchers. One scientist examined all prior estimates and concluded their flight speed is approximately 9 km/hr or 5.5 mph. For comparison, the average human jogs at a rate of 6–8 mph. 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 wing veins are lighter and narrower than those of females. Learn more about Monarch Butterfly