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V. cardui is one of the most widespread of all butterflies, found on every continent except Antarctica and South America. In Australia, V. cardui has a limited range around Bunbury, Fremantle and Rottnest Island. However, its close relative, the Australian Painted Lady (Vanessa kershawi, sometimes considered a subspecies) ranges over half the continent. Other closely related species are the American Painted Lady (Vanessa virginiensis), and the West Coast Lady (Vanessa annabella).
Vanessa cardui occurs in any temperate zone, including mountains in the tropics. The species is resident only in warmer areas, but migrates in spring, and sometimes again in autumn. For example, it migrates from North Africa and the Mediterranean to Britain in May and June, but having produced offspring they then die in the Autumn.
Relationship with humans
Vanessa cardui butterflies are raised in many pre-school classrooms to demonstrate the life cycle of a butterfly. Naturally, this is one reason they are so popular amongst children. They are also often found in science fair projects.
The egg takes 3 to 5 days to hatch. The eggs are tiny, as tiny as a sugar crystal. They are green and can be observed best with a magnifying glass. The caterpillar takes 7–11 days to turn into a chrysalis. At this stage the caterpillar eats a great deal of mallow and other types of plants. Before entering its chrysalis, the caterpillar will moult several times because of how quickly it grows in such a short period of time. The moult appears as a black speck, what looks like dirt, near the caterpillar. Many people believe this to be the excretion of the caterpillar, but it is truly the moult (the skin the caterpillar has grown out of). It takes 7–11 days for the chrysalis to turn into a butterfly. The painted lady butterfly travels around 1000 miles in its life. Its wing span is 2 inches. The painted lady caterpillar is black with spiked skin.
The caterpillars feed on a wide variety of host plants of the families Asteraceae, especially Carduus crispus (as implied by the species name cardui – Latin for "of thistles"). Also, Boraginaceae, Malvaceae (especially hollyhocks and dwarf mallow Malva neglecta), and a number of Fabaceae are eaten. The adults drink nectar from a variety of wildflowers and cultivars, more commonly the favored thistle, butterfly bush (Buddleja), asters, Tickseed sunflowers (Bidens) and zinnias.
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