Vanessa cardui migrations take place at high altitude, which explains why these migrations are seldom witnessed. "V. cardui" is known for its distinct migratory behavior. In California, they are usually seen flying from north to northwest. These migrations appear to be partially initiated by heavy winter rains in the desert where rainfall controls the growth of larval food plants. Painted lady migration patterns are highly erratic and they do not migrate every year. Some evidence suggests that global climatic events, such as el Niño, may affect the migratory behavior of the painted lady butterflies, causing large-scale migrations. Based on experimental data, the
Vanessa indica orange-red on disc, and across cell proportionately of less extent, and uniform, not getting paler towards the apex of the cell; the upper four spots of the preapical transverse series on the black apical area minute. It is about 5 inches (13 cm) in length. Hindwing: the postdiscal transverse band much narrower and shorter, not extending below vein 1, margined inwardly by a series of broad black subcrescentic marks; the tornal angle with a small patch of violet scales bordered inwardly by a short black transverse line. Underside very much darker than in "V. cardui", the orange red on the