Friday, March 1, 2013

Little brown paper sacks in the woods


From Michigan DNR

by Doug Reeves, assistant chief, DNR Wildlife Division
polyphemus cocoon
My wife and I were pulling dead grass and weeds from around the climbing rose in our front yard. We were preparing the rose for winterizing, and would be bringing the vines down from the trellis and covering them with straw or boughs to protect them from sub-zero weather. As I reached for another handful of grass, my eyes caught a sight that made me stop just before grabbing and yanking.
There, about 6 inches above the ground, was something that looked like it was made from part of a wadded-up, faded brown paper lunch bag. It was about 2 inches long and an inch wide, oval in shape. I imagine most people would not have given it a second glance. Yet, this was a special find for me. I had seen this particular kind of, “little brown paper bag” before. I had also seen some that were significantly larger and somewhat triangular in shape when viewed in two dimensions. I also had seen many similar but smaller ones hanging from wild cherry trees in midwinter, resembling nothing more than a lone dead, curled leaf that remained on the tree when the rest of the leaves fell.
polyphemus moth
This time I had discovered the cocoon of one of the giant silkworm moths, this particular one containing the metamorphosing caterpillar of an Antheraea polyphemus moth. I knew that in the spring a gorgeous, fawn-colored moth with big, dark blue eyespots on its hindwings would emerge from this cocoon, and even if I didn’t get to see the creature then, I certainly didn’t want to squash it now. The cocoon is still there as I write this (see the photo that accompanies this article). Chances of me actually seeing the moth when it emerges are very slim, but that is okay.
This time I had discovered the cocoon of one of the giant silkworm moths, this particular one containing the metamorphosing caterpillar of an Antheraea polyphemus moth. I knew that in the spring a gorgeous, fawn-colored moth with big, dark blue eyespots on its hindwings would emerge from this cocoon, and even if I didn’t get to see the creature then, I certainly didn’t want to squash it now. The cocoon is still there as I write this (see the photo that accompanies this article). Chances of me actually seeing the moth when it emerges are very slim, but that is okay.
Of the three cocoon types that I mentioned above, the polyphemus has been the rarest find for me. I have only found about five in my lifetime. I believe all the others I found were in clumps of willow or gray dogwood shrubs.
The other “little brown paper sacks” I mentioned above are the cocoons of Hyalophora cecropia – the triangular-shaped cocoon and largest of the three moths, having exotically beautiful red and white coloration over a background of brown – and the Callosamia promethea which is the smallest of the three but still a very large moth with dark chocolate-colored wings edged in tan. It seems somehow appropriate for such exotic-appearing moths to have exotic names. They are pronounced see-crow-pee-ah, pro-me-thee-ah and polly-fee-mus. The cecropia can have a wing spread as wide as nearly 7 inches, which is gargantuan for a North American moth.
Watch closely this winter and you may find a cocoon of one of these species. You just never know what awaits you on a trip to forest or field!  
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Thanks to Doug Reeves for the photo of the polyphemus cocoon.  The polyphemus moth photo is credited to:  Myers, Phil. Polyphemus moth. 2006. University of Michigan Museum of Zoology; The Animal Diversity Web (online). Accessed at http://animaldiversity.org.