Milbert's Tortoiseshells in Winter

Milbert's Tortoiseshells - A Great Find - And How They Survive the Winter

It seems like our best nature explorations come during the spring and summer months, and some in fall.  Nature exploration in winter comes at a higher price and usually requires heavy coats, hats and gloves.  The flowers are dead, and there isn't much greenery.  But for the dedicated, nature exploration can be found in all seasons, as illustrated in the stories below.

My son and I have decided to participate in the Outdoor Hour Challenges put out by Barb at http://handbookofnaturestudy.blogspot.com.  You can take a look at the November issue of the Outdoor Hour Challenge Blog Carnival, if you are interested.  December's issue will be coming out at the end of the month.

Two days ago my son was out exploring.  He turned over some boards that covered a hole on the hillside, and to his great surprise, he found two butterflies.  He knew they were butterflies because they had knobs on the end of their antennae.  I was surprised when he brought them in.

Milbert's Tortoiseshells

So we pulled out the butterfly books and figured out they were Milbert's Tortoiseshell Butterflies.  They are plain looking on the outside, but beautiful when they open their wings.  We learned that the adult Milbert's Tortoiseshell butterflies hibernate for the winter.  On a warmer winter day, they will wake up to take a drink of tree sap.  They can hibernate because of their body "produces glycerol, a chemical that drastically lowers the temperature at which ice crystals form. This prevents ice crystals from developing in the insect’s tissues and blood, which would damage cells. Combined with a sheltered, insulated hiding place, this natural antifreeze allows the butterfly to hibernate through the winter,"  according to Dr. Kenelm Philip, a senior research scientist at the Institute of Arctic Biology at the University of Alaska Fairbanks, in an interesting article about arctic butterflies printed in the Juneau Empire.

Most butterflies survive winter in egg form, and some in pupae (crysalis) form.  Mourning Cloaks, Question Marks, and Commas, along with the Milbert's Tortoiseshell hibernate in adult form in log piles, under bark and in crevices. The Monarch is the only North American butterfly to migrate south for the winter.

I found this to be a fascinating fact that I had never known before, even though I had studied butterflies when I was a kid, and even thought I might want to be come an entomologist.  I remember back when I was young, maybe around age 12 or 13, when I found a beautiful butterfly.  I was so surprised, because it was December 31.  The weather had warmed up to a clear sunny shirtsleeve day.  The butterfly was out wandering around in the sunshine just as I was.  I wasn't sure what kind it was.  I didn't have a butterfly book of my own yet, but as I look back on things, I'm pretty sure it was also a Milbert's Tortoiseshell.  I've wondered all these years about why it was out at such an odd time of year, but now I know.   It hadn't just hatched.  It was a well equipped surviver.

And so are the two butterfly beauties found in our yard this week.  It's amazing what you can learn when you take the time to search for the answers.  Now we know about how one more insect survives the winter.

And just so you don't worry, those two butterflies are back out under the boards getting their beauty sleep.  We hope to see them, and their children again in the spring.

(P.S. Don't kill Nettle plants.  That's what their caterpillars like to eat.)

Thanks to William for finding the butterflies and helping me research them, and decide what to write in this post.