The Carlisle Mosquito Online

Friday, October 23, 2009


Sulfur butterfly


The sulfur butterfly shown in the photo is probably the Clouded Sulfur, Colias philodice. It was photographed on a New England Aster on the Benfield Conservation Land near South Street on September 13. The asters were blooming near a stand of Smooth Sumac. (Photo by Tom Brownrigg)

There are two common sulfur butterflies in our region, the Clouded Sulfur and the Orange Sulfur, Colias eurytheme.They are similar in appearance, although the Clouded Sulfur is pale lemon yellow, whereas the Orange Sulfur has some orange on the upper wing surfaces. Both butterflies are common in open fields and have a dark border on the upper wings. However, the border is hard to see except in flight since they usually feed with their wings closed.

There is an “alba” (albanistic, or white) form of the female Clouded Sulfur that is indistinguishable from the “alba” form of the female Orange Sulfur. The two species also hybridize, making identification more difficult.

The Orange Sulfur is not native to New England. It was originally a resident west of the Appalachians, but spread eastward, in the late 1800s, with agricultural plantings of legumes. It became common in Massachusetts in the 1930s. My wife and I saw both Clouded Sulfur and Orange Sulfur at Towle Field on October 11. In my experience, Clouded Sulfur is the more common sulfur in Carlisle.


During the summer breeding season, males of both the Orange Sulfur and Clouded Sulfur may pursue a female Orange Sulfur. The female Orange Sulfur is able to distinguish the Orange Sulfur male because the male’s hind wings reflect ultraviolet (UV) light, which the female is able to detect. The male Clouded Sulfur’s hind wings absorb UV light, so the female Orange Sulfur is able to visually distinguish the Clouded Sulfur male as a different species. The two species also emit different pheromones that help with mate selection. Hybridization occurs when Clouded Sulfur populations reach very high levels, and mating occurs soon after the Orange Sulfur female emerges from the chrysalis and before she has developed the ability to distinguish males of the two species.


The caterpillars of both sulfurs feed on white clover, alfalfa, vetches and other legumes. Adults feed on nectar of about 40 different plants, including Queen Anne’s Lace, Purple Loosestrife, Joe Pye Weed, and goldenrods. I have seen the adults feeding on the flowers of several aster species this fall.

The larvae of both species exist over winter as a chrysalis (pupa) and emerge in May. The flight period of both species extends into early November in southern New England.


If you are interested in identifying butterflies, I recommend Jeffrey Glassberg’s book, Through Binoculars: A Field Guide to Butterflies in the Boston-New York – Washington Region. It has excellent photographs, and covers a more limited geographic region, namely Boston to Washington DC. There are also excellent photographs on the Massachusetts Butterfly Club website,

The Mass Audubon Butterfly Atlas website,, is a good source of information on food plants, life cycles and distribution.

Finally, if you are interested in caterpillars of both butterflies and moths, David L. Wagner’s book, Caterpillars of Eastern North America, is excellent.

What are you finding?

If you find something living or growing in your yard or on one of your walks in the woods and you think it might be interesting or you are just curious about it, drop me a note at


Note to locavores and foragers

Excellent edible mushrooms are now fruiting. These would include regular Oyster mushrooms (November 29, 2002), greenish-colored late Fall Oysters (November 16, 2007), Lobster mushrooms (August 1, 2008) which are the color of a cooked lobster, and the very tasty Hen of the Woods (October 10, 2006), also known as Maitake and Grifola frondosa, which seems to be prolific this year.

Autumn Olives (September 14, 2007) are still there for the taking. Some bushes have been picked clean already by the birds, but others are still heavy-laden.

Be sensible: don’t eat anything if you are uncertain of its identity. Resident Kay Fairweather is willing to consult if you have questions:

Seeing ladybugs?

Colder weather means that Asian Ladybugs and Western Conifer Seed Bugs are looking for a warm place to spend the winter. They might enter your home in huge numbers and can congregate, but they won’t do any harm. In the spring, they will look for a way out.

See the Mosquito archives at for more information on the Asian Ladybug (November 2, 2007) and on the Western Conifer Seed Bug (Januay 25, 2002).

© 2009 The Carlisle Mosquito