May: Butterfly of the Month
Painted Lady (Vanessa cardui)
In most years, the Painted Ladies arrive in hordes, recolonizing the northern part of the state from the warm deserts of southern California. They navigate northwest along the creek, laying eggs on thistle (cirsium species). This is not a true migration since there is no return movement of butterflies.
Painted Lady ( Vanessa cardui )
The vase-shaped bright green eggs hatch into a grayish-brown larvae with pale yellow lateral stripes and branched black spines. The caterpillars live on their host plants in colonies, easily recognized by the gauzy silk shelters they spin over the leaves while they are feeding. The chrysalis is gray-brown with yellow points.
Egg laid on Italian thistle ( carduus pyncnocephalus )
Larvae make shelters on thistle leaves.
Chrysalis just hours from eclosure
Since three species of Painted Lady are found here, how do you tell them apart? Cardui has a rounded wing tip with a white bar on the Upper Forewing; the West Coast Lady (annabella ) appears to have squared-off wing tips with an orange bar on the Upper Forewing. On the American Painted Lady (virginiensis ), look for two big eye spots on the Under Hindwing.
Another field mark is found on the Upper Hindwing. Annabella has blue spots ringed with black; cardui's spots are black while the same spots on virginiensis appear merged. Finally, virginiensis has a white dot near the edge of the Upper Forewing.
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