Coming out of the Woodwork

Spring is sort of a fickle thing around here. I was so sure we’d seen the last of the snow, then I woke up to white and howling north winds over the weekend. The only saving grace was that it didn’t last for long.

Weather isn’t a very reliable indicator of the seasons up in the north woods. I’m pretty sure the only month I haven’t seen flurries of some kind is July. However, there are plenty of other indicators of the impeding spring.

While returning birds are always a good sign, it’s when I see my first butterfly that I know we’re finally starting to thaw for the year. Usually sometime around early April, I spot one, a Mourning Cloak (Nymphalus antiopa, pictured) or an Eastern Comma (Polygonia comma), basking on a branch or the middle of a gravel road, soaking up the now warmth-giving rays.  It’s always an especially fun juxtaposition when I find one sitting on top of some snow that just refuses to melt and it makes me wonder: what is a cold-blooded insect doing up and about so soon in the spring?

The reason these butterflies can get an early start on things is because they spend the winter hibernating as adults. Actually, calling it hibernation is putting it lightly. They tuck their delicate bodies into old woodpecker holes, cracks in the tree bark or between the shingles and wall boards of old or unheated buildings and then they simply let themselves freeze. Okay, well not quite. While they do let ice invade their bodies, these butterflies are quite particular about where the crystals form, keeping them confined to the fluid on the outside of their cells so that vital systems aren’t destroyed.

As the days get longer and warmer, they literally come out of the woodwork, flitting around in the sunshine, even when there is a foot of snow on the ground. How these butterflies and other freeze-tolerant organisms know when to wake up is still a mystery. They’re basically in a state of stasis all winter, their lives set on pause, so what exactly constitutes their alarm clock is still an unknown.

Once they’re up and at it, however, there is no time to waste. Mating begins right away, with males and females fluttering around each other before settling down to business. Once the eggs are laid on suitable host plants, like willow, aspen and birch, these harbingers of spring die off, leaving their genetic legacies to the next generation. It may seem like a short life, but most of these over wintering butterflies have been alive as adults for up to 10 months, veritable ancients for their world.

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3 thoughts on “Coming out of the Woodwork

  1. This is a terrific post to herald your spring with, Heather! I find the hibernation of butterflies an astonishing phenomenon; here our winters are often cold and snowy but dotted with warm spells. A few days of each can sometimes be the case. Which means the odd juxtaposition of Nymphalis antiopa (called Camberwell Beauty in Europe) emerging for a day’s flight at the beginning of February, for example, and then retiring again, not to be seen until April. Their ability to not only pass the winters in a state of stasis, but also to be able to awaken and retire at will is a complex and extraordinary feat. Many thanks for sharing this.

  2. Thanks, Julian. It’s great to hear from you. I agree, hibernation of cold-blooded organisms is a fascinating phenomenon. I did a lecture on it earlier this year and I’m astounded by the physiology involved and all we still don’t know about the triggers.

    Thanks for letting me know about the European common name for our Mourning Cloak. I know how it got our name. I wonder where Camberwell Beauty came from.

  3. I saw the first butterflies about a week ago – one of the springtime thrills that puts a smile on my face. One of them was a very bedraggled and torn morning cloak (one of the few I can name). I knew that they hibernated, but I had no idea that they actually partially froze. That is amazing! And so is your image – so beautiful.

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