Vanessa cardui is the most widespread of all butterfly species. It is commonly called the painted lady, or formerly in North America the cosmopolitan.
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 (V. kershawi, sometimes considered a subspecies) ranges over half the continent. Other closely related species are the American painted lady (V. virginiensis) and the West Coast lady (V. annabella).
Adult butterflies feed on flower nectar and aphid honeydew. Females oviposit on plants with nectar immediately available for the adults even if it leads to high mortality of the larvae. This lack of discrimination indicates they do not take into account volatile chemicals released from potential host plants when searching for oviposition choices.
The availability of adult resources dictates a preference for specific areas of flowers. Flowers with more available nectar result in a larger number of eggs deposited on the plants. This reinforces the idea that the painted lady butterfly does not discriminate host plants and chooses mainly on the availability of adult food sources even if it increases the mortality rate of the offspring. The data also suggest that the painted lady butterfly favors quantity of offspring over quality.
Painted lady butterflies have a visual system that resembles that of a honey bee. Adult V. cardui eyes contain ultraviolet, blue, and green opsins. Unlike other butterflies, such as the monarch or red postman butterflies, painted ladies lack red receptors, which means that they are not sensitive to red light. Behavioral studies on the related species, Vanessa atalanta, have demonstrated that V. atalanta cannot distinguish yellow light from orange light or orange light from red light.
Groups of two to eight painted lady butterflies have been observed to fly in circles around each other for about one to five seconds before separating, symbolizing courtship. Groups of butterflies usually will not fly more than 4.5 m away from the starting point. To establish and defend their territories, adult males perch in the late afternoon in areas where females are most likely to appear.[36] Once the male spots a female of the same species, he begins pursuit of her. If the foreign butterfly is a male, the original male will give chase, flying vertically for a few feet before returning to his perch.
V. cardui establishes territories within areas sheltered by hedgerows. Vanessa cardui tend to inhabit sunny, brightly lit, open environments and are often attracted to open areas of flowers and clovers. Adults spend time in small depressions in the ground on overcast days.
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