In most years this butterfly is fairly common in our part of Wisconsin, but in some years we see only a few individuals all summer, in others we see hundreds of caterpillars and butterflies. The caterpillars eat stinging nettle (Urtica dioica), and in peak years the caterpillars can completely decimate the leaves on our nettle plants.
2005 was one of those peak years. In our July 21 butterfly count, we saw 134. We would have counted even more if we had walked the driveway earlier in the day, before the sun got too hot.
Caterpillars feed in groups, on top of nettle leaves.
The chrysalis has a beautiful gold sheen.
Nectaring on Common Milkweed
And basking on the driveway – where I most often see them.
Butterflies on the driveway – Milbert’s Tortoiseshells along with Red Admiral, Commas, and Compton Tortoiseshell
These butterflies overwinter as adults, so sometimes I see them very early in the spring. This is one that came out of its winter shelter to bask in the sun on March 19, 2011.