Four species of silkmoths were reported during the initial survey from 2002-2007: Cecropia Silkmoth (18 records), Promethea Silkmoth (7 records), Polyphemus Moth (10 records), and Luna Moth (28 records). Columbia Silkmoth (no historic records in Vermont, but found nearby in Quebec) and the exotic Ailanthus Silkmoth (one historic record) were not reported. It is difficult to determine if these moths are truly rare or if the paucity of records simply reflected observers focusing on butterflies as this was completed as a smaller companion project with the Vermont Butterfly Survey.
Giant silkmoth populations in the Northeast have apparently been in decline for years. One possible explanation is aerial spraying of Bacillus thuringiensis (Bt) to combat gypsy moths. This insecticide likely harms native insects as well. Research in Massachusetts found that an introduced parasitic fly, Compsilura concinnata, attacks and kills giant silkmoth caterpillars (Boettner et al. 2000, Elkinton and Boettner 2004). The fly was repeatedly introduced from 1906 to 1986 to control approximately 13 pest species, including a related silkmoth species. Concerns about the effect of this fly on native moths were expressed as early as 1919.
