CHICAGO (CBS) — State officials were asking the public to help in an effort to restore the population of a state symbol.

WBBM Newsradio’s Mike Krauser reports the monarch butterfly has been the state’s official insect for nearly 40 years , thanks to the lobbying efforts of a group of 3rd graders from Decatur.

Chris Young, spokesman for the Illinois Department of Natural Resources, said the butterfly’s numbers have dwindled since the mid-1990s.

“A key part of their habit is their host plant for the caterpillars, which are plants with the milkweed family,” Young said.

There’s no one factor to blame for the decline, according to Young, but everyone can help.

“A lot of times, problems seem so big, it seems like we can’t have an effect, but this is one place where you really can,” Young said.

He said a good place to start is by allowing milkweed to grow in your yard or garden. The plant is a host for the caterpillars that will grow into monarchs. One variety of the plant, the butterfly milkweed, has bright orange flowers.

“Plants like milkweeds grow readily along roadsides, edges of fields. They’ll do just fine on their own, as long as we let them,” he said. “If you tear the leaves, it’s got that white, milky sap – it’s really sticky – that comes out. That’s one of the things as a kid, when you’re out playing and you tear the leaves and you learn about that sort of milky sap.”

Birds don’t like the taste of the caterpillars that become monarch butterflies when the caterpillars feed on milkweed, so the plants offer them protection from predators.

The monarch butterfly is also the only butterfly that migrates great distances; wintering in Mexico. The roundtrip voyage takes four generations, so the butterflies you see showing up in spring aren’t the same ones that flew away last year.