Caterpillar foods: thistles, Burdock and hollyhocks; occasionally nettle, alfalfa, soybean, beet, borage, plantain (Bugguide)
The most widely distributed butterfly in the world. (BAMONA)
This species can’t survive our cold winters. It migrates up every year from warmer places. Some years there are big ‘invasions’ – usually at least several years apart. (Bugguide)
9/12/2003 This was a year of a big invasion.
7/10/2007 caterpillar in a nest on Field Thistle (Cirsium discolor)
7/10/2011 caterpillar nest
7/30/2017 This was another big migration year. I watched a female lay an egg on this Canada Thistle.
8/5/2017 The caterpillar grew for a while in a cage, but the plant finally wilted and the caterpillar wouldn’t move to a fresh plant.
5/21/2004 A late instar caterpillar from another year