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 viral disease affecting plums, damsons, peaches, apricots and some other plants. Brachycaudus cardui Brachycaudus cardui is a species of aphid, commonly known as the thistle aphid or the plum-thistle aphid. It infests trees in the genus "Prunus" in the spring and autumn, and mostly plants in the aster family in the summer. The viviparous wingless females of "B. cardui" have an oval or pear-shaped body and grow to a length of from . The colour may be green, yellowish, reddish or brown. The abdomen has a dark, shining patch on the dorsal surface, a fact which distinguishes this species from