Nature Notes by Dr. Frank Lang
News in the Medford Mail Tribune that large numbers of painted ladies were headed this way from California certainly caught my attention. I was only slightly disappointed to learn that they were butterflies. I was delighted to learn, however, that these butterflies are in the genus Veronica, and that there was a recent attempt to transfer them to the genus Cynthia. Wonderful names, it seems to me, for painted ladies.
Painted ladies have the distinction of being the most widely-distributed of all the butterflies. They are found throughout most of the northern hemisphere: Eurasia, Africa, North America and northern South America. Painted ladies of this type are absent from Australia and New Zealand. They don’t like cold winters. They can’t survive, so are transitory in temperate climes. They emigrate north from warmer southern latitudes, sometimes in prodigious numbers. In Oregon there have been major emigrations in 1958, 1966, 1973, and in 1992. Our entomologist, Marv Coffey, tells of going to a biology symposium on animal migration at Oregon State University in the spring of 1966 accompanied by a great northward emigration of painted ladies. John Dornfeld, author of Butterflies of Oregon recounts the same story.
We don’t know why painted ladies emigrate or how they navigate. Northward emigrations of millions of painted ladies correlate with optimum growing conditions in the year-round Mediterranean climate of their normal range. They move steadily northward, flitting and swirling within a few meters of the surface. Painted ladies are strong fliers. They have been observed flying 12 miles per hour against a strong headwind; 20 miles per hour with the wind.
Their movement north is not a true migration because they or their progeny generally do not return from whence they came. We refer to their movement as an emigration or pseudomigration. Although a few southward migrations occur, painted ladies seem to move from the safety of warm climates with no intention of ever returning south. Because of their excursions, they may someday survive year-round at northern latitudes if global warming continues.
Navigation is a puzzle. Some think polarized sunlight and/or the position of the sun provides orientation for butterflies. Other possibilities include the use of landmarks or, if flying at night, the moon or stars. They will layover if weather is cold and blustery, but moderate winds do no deter them.
As adults move north they use their stores of reserve fat and arrive at their destination somewhat the worse for wear. There is enough triumph left for reproduction. Painted ladies feed on 100 or so different plants, especially thistles, mallows and legumes. They are found on yerba santa, a plant humans use as a stimulating expectorant and the mask quinine’s bitter taste.
When you are out enjoying nature, look for medium sized orange-ish butterflies with eyespots aft, and blackish wing tips forward with white bars. They are painted ladies headed north.
— Dr. Frank Lang