The last eastern population of a rare butterfly lives on a Pennsylvania military base. Here's how to see it.

The only remaining eastern population of a rare butterfly lives on a military base in Pennsylvania, and starting this week, tours will be available for those hoping to catch a glimpse. 

The eastern regal fritillary butterfly has made its home at the 17,000-acre Fort Indiantown Gap National Guard Training Center in Lebanon County. 

While it may seem like a strange place for such a rare butterfly species to live, the Pennsylvania Department of Military and Veterans Affairs says the active military regime on the installation combined with land management and conservation provides the right amount of disturbance for the early-successional grassland habitat that the butterflies need. 

For those who want the chance to see the eastern regal fritillary butterfly, wildlife staff at Fort Indiantown Gap will provide tours on June 29, July 1, July 8 and July 10. More information about registering can be found online.

The regal fritillary butterfly and its declining numbers began to get more attention in the mid-1990s. The Fish and Wildlife Service says habitat alteration has reduced its range and abundance, because the butterflies need specific food plants and places to live and grow during critical stages of their life cycle. 

Since then, biologists at Fort Indiantown Gap have been working to develop conservation plans and implement management strategies to help keep the existing population strong. 

The long-term goal is to expand the eastern regal fritillary's current range through reintroduction efforts. The military base has been working with Zoo America North American Wildlife Park since 2011 to develop a captive rearing program.