Friday, April 16, 2010
Eastern Comma Butterfly
In the great cosmic scheme of things there is a stronger connection between warm weather and beer than I had previously realized. My two potential topics for this week’s column were the Eastern Comma butterfly and the shrub called Sweet Gale which is now flowering in the Cranberry Bog. Both are evidence that the weather is warmer and both have a connection to beer. The caterpillars of the Eastern Comma like to feed on the leaves of hops. Brewers, traditionally in Scotland and Scandinavia, sometimes flavor their beer with Sweet Gale instead of hops. I take this as another sign of the never-ending wonders of the balance of nature. When caterpillars eat the hops, nature provides us something else to put in the beer. Being more partial to butter than to beer, I have chosen the butterfly.
Name: The Eastern Comma butterfly is Polygonia comma. It also goes by the common name of Hop Merchant. It is a member of the Brush-footed family of butterflies, so-called because the front legs are vestigial, hairy and brush-like. Within the brush-foots, the Eastern Comma is a member of a sub-family called Anglewings. The genus name, Polygonia, comes from poly meaning many and –gonia meaning angle. It refers to the indentations along the edges of the wings. The sub-family includes the Green Comma, Gray Comma, Hoary Comma, and yes, the Questionmark. The Commas have a silver mark in the shape of a comma on the underside of the hind wing. The inquiring member of the family, the Questionmark, has the silver comma but also a silver dot forming a question mark.
When and where seen: The Eastern Comma in the photograph was flitting about in a sunny opening in the Towle woods on April 4. I may have seen one a couple of weeks earlier on one of those very warm days in March – also in the Towle woods – but I didn’t catch it and confirm the identity. The ones we see in the spring have spent the winter as adults. They will be around through May and their offspring will emerge from late June through late August. The second brood will emerge from early September to early November.
Identification: A lot of clues to the identification are in the name and family associations. At first glance, Brush-footed butterflies look like they have only four legs. The Anglewings have obvious indentations on the wing margins. The Commas have the silver comma on the wing. The color on the upper wing surface of the Eastern Comma is different in the summer and winter broods. The winter brood, out now, has orange with black markings on both fore and hind wings. Also, the hind wing has a broad margin with a row of yellow spots. In the summer brood, the hind wing is more dark brown than orange, and the wings have a violet border. The underside of the wings is mottled grey and brown – designed for camouflage when the butterfly alights and holds its wings together. The Mass Audubon website at www.massaudubon.org (search for “Eastern Comma”) has good photos of both summer and winter broods and a convenient system for side-by-side comparisons of different species.
Behavior: The Eastern Comma shares much of its behavior with other Anglewings. They tend to be wary and dart rapidly. The adults seldom feed on flower nectar. They prefer tree sap, rotting fruit and animal droppings. Their usual alertness is compromised when they become intoxicated from feeding on fermented fruit.
Caterpillars: The caterpillars are very spiny. The ground color varies from green, yellow, white to black. The pale kinds have black markings. In addition to hops, they feed on various kinds of nettles and on elm. I have seen hops along the side of Baldwin Road and in Great Brook Farm State Park but so far not at Towle. I will keep a sharper eye out for all these host plants at Towle in the hope that I find a Comma caterpillar.
Crops of hops: The Eastern Comma’s alternate common name of Hop Merchant comes from the way hop farmers interpreted the metallic markings on the chrysalises they found in their crops. Golden markings supposedly foretold a high price for the hops while silver markings were a sign of lower prices.
References: Butterfly Atlas at massaudubon.org; Robert Michael Pyle, Audubon Field Guide to North American Butterflies, David L. Wagner, Caterpillars of Eastern North America; BugGuide at http://bugguide.net/node/view/5509
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