Friday, April 7, 2006
Mourning Cloak Butterfly
When and where seen: On March 29 when it was sunny and warm, around 60 degrees, I was in my front yard and the shadow of a rather large butterfly caught my eye. It turned out to be a Mourning Cloak. About 30 minutes later, I saw a pair of them dancing a kind of aerial jitterbug and flying higher and higher up to the top of the pines where I lost sight of them. Last fall, on October 17, while I was in the yard inspecting tree trunks for lichens and tiny mushrooms, I disturbed a very well-disguised butterfly on an oak tree. It flitted about in the woods among the falling leaves and eventually came to rest on a boulder in the sun. Most of the time it kept its wings in a vertical position but some of the time it flattened them against the boulder and showed the bright colors on the top side and I could tell it was a Mourning Cloak. It allowed me to get very close.
Identification: This is a fairly large butterfly with a wingspan of around 3 inches. The edges of the wings are jagged. The underside of the wings is drab and mottled and provides excellent camouflage when the butterfly is resting on bark with its wings held together over its back. The topside of the wings would not be mistaken for a traditional mourning garment! The markings are colorful and bold. There is a border of yellow around the outer edges. Inside the border is a row of bright blue spots on a black background. The body of the wings is a rich velvety brownish maroon. There is a couple of short yellow stripes on the leading edge of each of the first pair of wings.
Life cycle: If you see a large butterfly early in spring, late in the fall, or even in the winter, it could well be a Mourning Cloak. It winters over as an adult butterfly. Even though it is the only Massachusetts butterfly that has been recorded flying every month of the year, it spends most of the winter in a kind of hibernation. It finds protection from the cold under loose bark and also gets protection from a natural antifreeze which it secretes. In spring, it emerges to mate. The female then lays eggs on willow, elm, aspen or hackberry. The eggs completely encircle the twigs of the host plants. A web site on the natural history of Orange County, California has an excellent page of photographs showing Mourning Cloak eggs and caterpillars at many stages of development. The URL is a long, segmented thing rather like the caterpillar. Google can find it for you. The new generation of adults emerge from their pupae in June or July and spend the summer in idle estivation. They come out in fall to feed and create a store of energy to get them through the winter. This lifestyle allows the adult to live as long as 10 or 11 months, the longest life span for a North American butterfly.
References: Audubon Society Field Guide to North American Butterflies, Robert Michael Pyle; Northern Prairie Wildlife Research Center at http://www.npwrc.usgs.gov; A Guide to Observing Insect Lives, Donald W. Stokes.
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