A Palos Verdes blue feeds on a honey-water mixture. Males are largely blue; females appear gray. The butterflies are making a comeback from the brink of extinction because of a breeding program's success.

Los Angeles ? Hidden by the darkness of a half-moon sky, nine students and their biologist mentor waded through waist-high brush one recent night, hunting for yellow-flowering deer weed to shelter one of the rarest butterflies in the United States.

One student hugged a big, red cylindrical cooler. “I come bearing endangered species,” she said.

It was no joke. Inside the cooler fluttered dozens of Palos Verdes blues, thumbnail-sized butterflies, all bred in captivity, most just a few days old.

The biologists’ mission on a Palos Verdes Peninsula hill: Free the blues.

This was a rare moment in the race to save the federally protected butterfly, which hovered near extinction two years ago. Now, government officials have an unexpected problem on their hands: A breeding program has been so successful that there are too many butterflies and not enough federally approved sites where they can be released.

A place for butterflies

Last spring, an estimated 220 of the species existed in the wild, so few that experts feared they could be wiped out by a single hillside brush fire. Yet in 12 days earlier this month, 2,400 blues – three times more than forecast – emerged at a laboratory housed at Moorpark College, about a 45-minute drive to the northwest from Los Angeles.

As a result, federal wildlife officials are scrambling to identify more sites on the Palos Verdes Peninsula to release the rare butterfly. But with a life span of three to 38 days, hundreds of the butterflies may die in captivity.

“We’ve accommodated what we can with the areas that are currently available,” said Jane Hendron, spokeswoman for the U.S. Fish and Wildlife Service, charged with protecting endangered species. “They may not all get a chance to live in the wild.”

Biologists can’t simply release the butterflies in any nice-looking garden or park. This is a federally protected species, after all, and there are regulations to follow. Also, landowners must be willing to accept the butterflies with all their protections. Permits can take months. Officials fear publicity could attract butterfly poachers.

Even if far fewer butterflies had emerged this year, federal officials initially had no landowners permitted and willing to take them.

So when a coastal bluff was approved for a release recently, scientist Jana Johnson met her students in a kind of undercover biological mission.

It quickly ran into trouble. Winter rains had produced a profusion of wildflowers, and it was too dark to distinguish deer weed from mounds of yellow-flowered mustards and black-eyed Susans. Undeterred, team members gathered up coolers and shopping bags holding 206 butterflies and headed into the brush.

Comeback

In 1983, biologists counted no more than half a dozen blues on the peninsula. A year later, none could be found. At the time, experts called the butterfly the first federally protected species to go extinct in the history of the Endangered Species Act of 1973.

Nine years later, biologists spotted 100 blues on military land in San Pedro, and the race began anew to keep the species from “winking out” for good.

The Fish and Wildlife Service launched a captive butterfly breeding program in 1994, and Johnson began raising butterflies two years ago. Johnson, 38, is credited with the butterflies’ success.

Biologists expected only 25 percent of the pupae produced last year to successfully yield butterflies. The yield instead was 60 percent. Johnson credits an unanticipated alignment of “cues”- sun, temperature, even pheromones drifting from one pupae to the next.

When Johnson got word that an undisclosed landowner would allow a release, her team sprang into action. Butterflies, however, cannot be rushed.

Students began transferring butterflies by fingertip, one by one, from cages to plastic bowls. The sunset had faded to black by the time the team reached the site and began looking for deer weed.

Drivers left their cars lined up, engines running, headlights on bright to cast a glow as they hiked into the brush.

Release

“If anyone had ever told me I would be crazy about butterflies, I would have said they were crazy,” said one student as she maneuvered a narrow road. Now, she is at the laboratory by 6:30 a.m. and has nightmares of squishing a pupae by accident.

The deer weed resembled yellow pillows of flower-studded stalks glimmering in the headlights. The students chose plants and opened the bowls.

They lifted each rare butterfly with a grace born of practice and guided it to a deer weed plant. The blues settled softly into the leaves.