Nature Notes: Minnesota has butterflies that hibernate

Many years ago someone alerted me to some butterfly species that spend the winter as adults in hibernation. On extremely warm winter days, or on early spring days, it is possible to observe one flying about the landscape.

Minnesota is home to 172 species of butterflies, only nine of which stay over in winter. Some of them include the red admiral, question mark, mourning cloak, Compton's tortoiseshell and Milbert's tortoiseshell. They hibernate under loose bark, in hollow logs and trees, under eaves or in buildings, and they appear on days when the temperature reaches 50 degrees.

Last year the Twin Cities recorded the first 70-degree day March 15; it was the high temperature for the month and a new record for the date. And, yes, a mourning cloak butterfly was seen on the wing. The mourning cloak is a long-lived, hardy species that is plentiful throughout Minnesota and throughout the eastern half of the United States and Canada. It is also a familiar sight in many temperate areas of Asia and Europe. It is called the Camberwell Beauty in England.

It is an exceptionally beautiful butterfly, dark velvety-brown with a yellow-gold border on its wings and blue dots on the margins between the brown and gold. The wingspread is about 3 inches. The first new adult generation emerges in late June or early July, and the second-generation adults appear in September. Some fly about through the month of October, and I have occasionally seen them as late as mid-November.

Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. He taught and worked as a naturalist for 50 years.