GRAND RAPIDS, Mich. (WOOD) — Endangered butterfly caterpillars at the zoo in Grand Rapids have been moved safely into a controlled environment to wait out the winter.

The Poweshiek skipperling is a species of tiny butterfly that was once common in the Midwest but is now endangered. John Ball Zoo is part of an effort to try to save them.

“Last summer, when they went looking out for wild butterflies, they only found a handful, maybe 10 or 20 in the entire range. And right now we have about 500 caterpillars that we are overwintering at the zoo,” John Ball Zoo curator Dan Hemmann said.

The zoo has prepared its latest batch of caterpillars for winter, storing them in vials and placing them in an environmentally controlled chamber. Once in that chamber, which is kept at 25 degrees, the caterpillars enter diapause — a sort of deep sleep in which they stop growing. After about six months, the caterpillars will come out of the chamber and eventually grow into butterflies.

The Poweshiek skipperling is a critically endangered species. Conservationists estimate there are only a few hundred left in the wild. (Courtesy MSU Extension)

“We’d like to keep breeding and using that population to not only to be an insurance population, so if those butterflies do become extinct in the wild, they still exist…” Hemmann said. “And the hope is to eventually figure out why they are becoming extinct to not only improve the habitat for the butterflies but for the other animals and then reintroduce them (to the wild).”

The butterflies fly once only a year for about a week, usually around the Fourth of July. During that time, they lay their eggs before they die. The caterpillars grow slowly over the fall before wintering.

This is the second winter for the zoo’s Poweshiek skipperling program.