Butterflies of Dry Woods and Shale Barrens

In the Sideling Hill Creek watershed, and other hot dry shale places in south-central Pennsylvania, there is a special habitat known as the shale barren. These open rocky places and nearby dry woodlands are home to at least a dozen or more known rare moths and butterflies. Although inventory work is incomplete, we know that one very rare species is the Olympia marble (Euchloe olympia). This delicate mid-April to mid-May flyer, is strictly linked to certain native plants of the mustard family (Cruciferae), which are the sole food plants for the marble's caterpillars. The adults feed on the nectar of plants that are also adapted to these same shaly environments, such as the bird's-foot violet (Viola pedata), pictured here.

Through the Pennsylvania Natural Heritage Program (PNHP), WPC staff are collecting and providing data about rare species like the Olympia marble. Because such species are potentially vulnerable to the use of pesticides in their habitats, the Pa. Department of Conservation and Natural Resources uses the PNHP database as part of its conservation planning. The database is consulted during preparations for controlling outbreaks of pest species, such as the gypsy moth (Lymantria dispar). In this way, aerial applications of pesticides applied during the same time some rare insects are feeding and laying their eggs, will not be applied to the special habitats they occupy.

This photograph, taken in Bedford County, was provided by Rob Criswell.

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