Uncertain Taxonomy

Clouded Sulfur

A year ago lightning ignited the Cove Fire in the Modoc National Forest near Adin CA (Modoc County). About 31,000 acres were burned before the fire was contained. Since then Leonard and periodically return to a site along Forest Road 40N11 to document the forest’s recovery from the fire. Last month we were pleased to see many clouded sulfur butterflies (Colias philodice) amid  the lupines. I think they were clouded sulfurs. . . then again. . . .

Also colloquially called a common sulfur, C philodice is found throughout much of North America. There are differences between the eastern and western clouded sulfurs. Some taxonomists believe these are two separate species and have given the eastern form its own species designation (P eriphyle). Where the eastern and western co-occur they hybridize.

To add to the confusion there is another butterfly, the orange sulfur (C eurytheme), that closely resembles the clouded sulfur. These butterflies rarely perch with their wings open in the field. The males of both species are bright clear yellow. The forewing undersides have some dark submarginal spots while the hind wings have a silver cell spot, usually doubled, rimmed with orange pink. The females may be yellow or a greenish white and have an uneven darker edging around the cell spots. The main difference between the clouded and orange sulfurs is an orange tint or blush to the underwings and more orange on the upper side of the wings. But unless one captures the butterfly and examines the upper side of the wings, it is difficult to distinguish between the two species, particularly because they also interbreed.

Clouded sulfurs and orange sulfurs inhabit open areas including fields, lawns, meadows and road edges. Both species particularly favor alfalfa fields. The adults feed on nectar from a variety of plants. The caterpillar host plants are mainly members of the Pea Family (alfalfa and lupine belong to that group).

This bright yellow butterfly, I believe, is a clouded sulfur. Then again, it may be an orange sulfur or a hybrid of the two. Definitive field identification of these two species is difficult. No matter what the species, it was a welcome sight in a forest area so recently devastated.

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