Blog Post Update – September 20, 2017: On August 8, I blogged about a flight of Painted Lady butterflies here in New England and elsewhere on the continent. I speculated that these were southbound migrants. Well, I was wrong. These ladies of August, present for about a week, were either northbound or a brood producing what is now the biggest fall Painted Lady flight I’ve ever seen. Nearly everywhere I walk here in Montpelier, including downtown, I’m finding these lovely butterflies. They’re more abundant now than Monarchs. So here’s an updated version of my post [with new text in brackets].

NOW PASSING YOU BY is one of the planet’s great events — an epic migration like no other. Not whales. Not birds. Not caribou. Painted Lady, the world’s most widespread butterfly, is on the move. We’ve been seeing them bigtime here in New England the past few weeks.

Painted Lady (Vanessa cardui) flies on every continent except Antarctica. From a vantage above, you see a fairly standard butterfly: lots of orange, black and white, with azure gems sometimes showing on the hind wings. Flashy and pleasant, to be sure.

But, ah, the Lady’s underside. Jackson Pollock and Peter Max might have been inspired (or envious). From below we receive a palette of peach and purple, almond and mauve, along with undulating white veins and dark edges. A fitting ornament atop that Purple Coneflower in our garden last week here in Montpelier.

Unlike lots of temperate butterflies, the Painted Lady has no tolerance for a freeze — certainly not as an adult, but neither as egg nor caterpillar nor chrysalis as well, which is how most of our butterflies get through the winter around here. So the Lady leaves.

“Migrants fly fast and straight, rising over obstacles in their path (from trees to six-storied buildings), rather than detouring around them,” write Rick Cech and Guy Tudor in their masterpiece Butterflies of the East Coast. “Migrants are encountered with some regularity at sea.”

We sometimes get great Painted Lady invasions — massive northbound flights — in the spring. The southbound flights generally aren’t as dramatic in terms of numbers. [This year they are.] One question is whether we’ve been [we were] seeing a northbound or southbound flight [in August]. Adults fly north from spring through July, returning south from late July or August into fall.¹ I suspect we’ve been seeing southbounders. [Now, in September, we’re seeing southbounders.]

What makes this butterfly so cosmopolitan isn’t only its peregrinations. It’s also diet. Unlike many butterflies, whose caterpillars feast only on one or more host plants, Painted Ladies are botanical omnivores; the caterpillars are known to survive on more than 100 species from about 10 plant families. Find them chewing on thistles (also a fine nectar source for adults), mallows, sunflowers and legumes, among other plant groups.

You can find the adults nectaring on anything they can find this fall. [They were sucking up Purple Coneflower nectar in August.] Now, in September, I’m seeing them on asters, goldenrods and common garden flowers. By the way, we’re getting a decent Monarch flight this fall as well.²

So enjoy the gossamer flights. And by all means kneel — or genuflect — for a glimpse of the Lady’s undersides.

[My colleague Kent McFarland at the Vermont Center for Ecostudies also reports on the Painted Lady flight and how you can help track it.]

Here are Painted Lady sightings reported to iNaturalist during May, June and July (along with the first week in August in that July map.) Note how we’re doing a good job finding and reporting them here in Vermont! [At the end of the month, I’ll add maps for August and September, which will no doubt be dense with Painted Ladies.]

Source: iNaturalist (http://www.inaturalist.org)

References

¹ The Butterflies of North America by James A. Scott.
² http://monarchwatch.org/blog/2017/07/20/monarch-population-status-31/