State officials have announced the discovery of a rare frosted elfin caterpillar in Western Massachusetts, suggesting decades of painstaking work to protect the butterfly species in the area have begun to pay dividends.

MassWildlife said that the frosted elfin caterpillar was recently discovered at the Montague Plains Wildlife Management Area, about 1 mile from the nearest known population.

The frosted elfin butterfly is designated as a species of special concern in Massachusetts, where they can only be found at about two dozen places.

The small, brown butterflies lay eggs only on sundial lupine and yellow wild indigo plants, according to state wildlife officials, who said they faced a daunting task to protect the species when it acquired the bulk of the Montague area in 1999.

At the time, decades of agricultural plowing and abandonment, along with wildfire suppression, had vastly inhibited the unique characteristics of the pine barrens habitat that allows the elfin to thrive and spread its wings.

Only a few scattered patches of unplowed land contained the residue of a more diverse habitat and native plants, officials said. But wildlife officials set to work, locating a few small remnants of sundial lupine on the grounds and taking steps to bolster lupine growth.

Staff also collected seeds from lupine and from little bluestem grass in the area and worked to expand existing patches of the native plants, officials said. The original quarter-acre remnant of little bluestem has since ballooned to nearly 20 acres.

“The unique barrens habitat at Montague Plains WMA is considered regionally and globally rare, making our restoration efforts at this site especially important for rare animals and plants that require this special habitat type,’’ Brian Hawthorne, MassWildlife’s habitat program manager, said in a statement.

A number of other species are benefiting from the growth of lupine and other plants in the area, including rare moths, butterflies, native bees, and reptiles such as the Eastern hognose snake and Eastern box turtle, officials said.

Travis Andersen can be reached at travis.andersen@globe.com.