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
Brachycaudus cardui have pinkish blotches on a dark green background. "B. cardui" has a wide distribution in Europe, Asia, North Africa and North America. The primary host of "B. cardui" is plum, cherry, apricot, peach or damson, but during the summer months it moves to a secondary host. This is often a thistle in the genera "Carduus" or "Cirsium" where it is commonly seen on the stems and flowerheads. Alternatively, other plants in the aster family or plants in the borage family (Boraginaceae) may be used as secondary hosts. Winged individuals fly back to the primary hosts in the autumn. Colonies of