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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. It migrates from North Africa and the Mediterranean to Britain in May and June, but for decades natualists have debated whether the offspring of these immigrants ever make a southwards return migration. Recent research suggests that British painted ladies do undertake an autumn migration. Using an entomological radar, scientists at Rothamsted Research provided evidence that autumn migrations take place at high altitude, which could be why these migrations are seldom witnessed.
Relationship with humans
Vanessa cardui butterflies are raised in many preschool and elementary 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.
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- Vanessa cardui, Butterflies of Canada
- Opler, P. A. and A. B. Wright. 1999. Peterson field guide to western butterflies. Houghton Mifflin Co., Boston. 544 pp. ISBN 0-395-79152-9
- Chapman JW, Nesbit RL, Burgin LE, Reynolds DR, Smith AD, Middleton DR, Hill JK. 2010 Flight orientation behaviors promote optimal migration trajectories in high-flying insects. Science 5;327(5966):682-5
- Nesbit RL et al. Seasonally adaptive migratory headings mediated by a sun compass in the painted lady butterfly, Vanessa cardui Animal Behaviour