‘Endangered’ butterflies reintroduced at secret sites in Pennsylvania Posted May 14, 2021 Tiny, first-instar caterpillars of the rare regal fritillary butterfly are placed on violet leaves on a state game lands. (Pennsylvania Game Commission photo) Facebook Share Efforts to re-establish populations of a once common, native butterfly that today persists in the East only at Fort Indiantown Gap in northern Lebanon County and the Radford Army Ammunition Plant in Virginia – have gotten a boost this year. The success rate for raising caterpillars of the regal butterfly in a lab at ZooAmerica in Hershey for release onto new sites in Pennsylvania has climbed from 15 percent to 60 percent, according to Mark Schwartz, a wildlife biologist with the Pennsylvania Department of Military and Veterans Affairs Environmental Office at Fort Indiantown Gap.