Are the occurrences of remnant lepidopteran populations consistent with Compsilura concinnata as an agent of moth extirpation in New England?

The 20^th century northeastern regional decline of wild silk moths and certain other macrolepidoptera has been noted for decades, and variously attributed to factors ranging from widespread deployment of pesticides to light pollution and introduced parasitoids.  Whatever their respective impact, our understanding of these factors is complicated by land use history and generalized habitat fragmentation.  The high concentrations of regionally rare or threatened Lepidoptera on Massachusetts’ offshore islands includes species such as Eacles imperialis (Saturniidae) and Datana contracta (Notodontidae) that have declined or been extirpated from mainland New England.  Remnant island populations of declined silk moths—in particular where the introduced parasitoid Compsilura concinnata has not yet been recorded—may corroborate the fly’s primary role in the decline of certain moths.  Although historical faunal data for Massachusetts’ offshore islands suggest significant turnover in moths and document more than 50 species of native tachinids, any simple, unambiguous attribution of faunal change to C. concinnata is confounded by variability in vegetational history and the history of baseline entomological faunistic data.  Combining historical records and our own samples of over 300 traplines set in 2010 and 2011, we revisit the composition of tachinid species on Martha’s Vineyard and Nantucket, the two largest islands and the areas which support the highest concentrations of regionally threatened moths.