Standing in a tent at Baltimore's zoo, Sue Muller bends over a small box, probing with a paintbrush for the squirming caterpillars hidden among wilted green leaves.
Muller and fellow volunteer Louisa Stevenson work quickly but carefully to feed and clean the 23 larvae inside. The caterpillars look like short pieces of pipe cleaner. But soon, they will emerge as colorful - and scarce - Baltimore checkerspot butterflies.
The checkerspot - Maryland's official insect - has been in sharp decline due to the ravages of deer and development on their very specialized habitat of turtlehead plants.
But a breeding experiment begun last year at the Maryland Zoo in Baltimore may help reverse that, participants said.
Last summer, project participants caught eight pregnant females in the wild - some from as far away as Garrett County - and brought them to a camping tent set up at the zoo where the butterflies laid eggs on the underside of turtlehead leaves.
Mature butterflies live for about 10 days each June, mating and laying eggs. The eggs hatch each summer, and the young caterpillars eat the leaves where they emerge, molting periodically as they grow. Eventually, they crawl down the plant and burrow into the ground for winter.
In spring, they climb back up and begin eating until they take flight on orange, white, red and black wings - colors that match the colors of Maryland's founder Cecilius Calvert, the second Lord Baltimore.
That's the point where the volunteers' intervention and protection is most crucial.
"We've had phenomenal success. We produced hundreds of larvae last summer," said Pat Durkin, co-founder of the Washington Area Butterfly Club and coordinator of the Baltimore Checkerspot Butterfly Restoration Project of Maryland.
The project also has received support from the zoo, the American Zoo and Aquarium Association, the National Fish and Wildlife Association and the Maryland Entomological Society, plus tips from a checkerspot expert in Colorado.
The program has had educational benefits as well.
High schools in Baltimore City and Baltimore and Howard counties are promoting the program and spreading the word about planting turtlehead plants, said Jamie Lynch, government and foundation relations manager for the zoo.
The zoo also will erect a display tent in its Maryland Wilderness Area.
"As an organization committed to conservation, we're thrilled," Lynch said.
Muller, a Howard County recreation and parks department naturalist, tried to spark a checkerspot comeback in 2001, when she organized construction of several small fenced turtlehead enclosures in Elkridge and Clarksville. She saw a few butterflies, but there were too few to sustain a colony, she said.
Durkin also tried to breed them in her Washington, D.C., home garden, but without lasting success, and a Montgomery County enthusiast brought checkerspots to his farm from Massachusetts, but they didn't thrive in Maryland, Durkin said.
Now, with the wisdom of four years of experience and help from a number of groups, Durkin hopes this year will mark real progress.
In addition to the 23 at the zoo, groups of larvae wintered at the zoo's turtle bog, at Durkin's house, on a farm in Montgomery County and elsewhere in Maryland, she said. Some even escaped into Druid Hill Park after plants they burrowed beneath were moved to the zoo's greenhouse.
But Durkin said that's fine, since the eventual goal of the project is to see Baltimore checkerspots thriving throughout Maryland.
"We're really ecstatic," she said, though a remaining worry is whether the butterflies will mate successfully in captivity.
Normally, only 1 percent of eggs survive to spread their wings. But Durkin said the humans protected this group from predators and parasites.
A bumper crop of new butterflies should begin emerging in the middle of next month.
For now, the two volunteers go to the zoo each day to carefully open and clean each plastic box, measuring fresh food and writing everything down on a log kept in the tent. They use their soft paintbrushes to move the delicate caterpillars to avoid hurting them.
"Only the best for our caterpillars," Muller said.