Scientists have tried at least five times in the past few decades to establish a second wild Oahu population of the endangered orangeblack Hawaiian damselfly, a smaller relative of the dragonfly.

This time, backed by a new and robust captive rearing program and a full year of releases in the wild, they have never been more optimistic.

“This is the first time we’ve seen a second generation in the wild,” said William Haines, research entomologist with the state Department of Land and Natural Resources’ Hawaii Invertebrate Program. “It’s really encouraging. It tells us we’re doing something right and we’re getting closer.”

The orangeblack Hawaiian damselfly — one of about 25 species of endemic damselflies once found only in Hawaii — was described in the early 1900s as one of the most commonly observed insects on Oahu, seen in gardens and low-­elevation taro patches, ponds and freshwater habitats all over the island.

Scientists say the damselflies play a key role in Hawaii ecosystems, providing food for native birds, as pollinators of native plants and as recyclers of nutrients. They also help control mosquitoes, midges and other pest insects.

Ironically, the sorry plight of the orangeblack damselfly is tied to another species that was imported to Hawaii in the early 1900s to help control mosquitoes. The problem: the mosquitofish also feeds on the immature, aquatic stage of the damselfly.

The orangeblack damselfly soon began to disappear, and by 1979 the delicate insect was nowhere to be found, believed to be extinct on Oahu.

That was the case until a small population was discovered on the grounds of Tripler Army Medical Center in 1994. The damselflies had found a sanctuary in a remnant section of a stream that still flows in the midst of an urban environment.

“It’s a hospital, a functioning hospital, so all the facilities that go along with that are around and influencing that stream. It’s not a super stable place for that population to exist,” said Kapua Kawelo, the U.S. Army’s Natural Resources program manager on Oahu.

With small and vulnerable populations also on Maui, Molokai and Hawaii island, the orangeblack damselfly was finally added to the U.S. Endangered Species List in 2016, one of six native damselflies on the list.

The last time there was an attempt to establish a second Oahu population was two years ago in a pond cleared of predatory fish at the University of Hawaii’s Lyon Arboretum.

Immature damselflies, or naiads, from the state’s captive rearing facility were released into the pond and grew to adulthood just fine. But the adults preferred a sunny and open loi found elsewhere at the arboretum. Unfortunately, the loi was infested with mosquitofish.

“The damselflies didn’t know that and ultimately it was not successful,” Haines said.

The latest reintroduction is at a small, spring-fed stream near Dillingham Airfield.

Every week for the last year, biologists and technicians with the Army and the state Division of Forestry and Wildlife have been taking hundreds of adult damselflies raised at the rearing facility and releasing them along the Dillingham stream.

With captive rearing techniques improving over time, Haines figures they’ve released nearly 4,500 damselflies at Dillingham.

Next month the team will stop releasing damselflies and see what happens, hoping that a sustainable population will thrive on its own.

Haines’ optimism is buoyed by the number of second-generation damselflies he’s observed in recent months.

How does he know which damselflies are second generation?

All the released damselflies have a small unique number marked on their wings, and they are starting to see individuals emerging from the stream that are not marked, which means they are wild-born.

“That’s really encouraging to see they’re completing their entire life cycles in the wild,” he said.

But wait. Small numbers on wings? Haines says a technician actually marks each damselfly with a fine-tipped marker. No joke.

While that sounds like a nearly impossible operation to perform on a skinny, 2-inch flying insect, he said it’s not as hard as it sounds. The damselfly has an accommodating trait in which it drops and plays dead whenever it is afraid or being harassed. That leaves a minute or so to mark the number.

In the field, he said, the second-generation damselflies get a new number penned with a red marker.

Of the 107 damselflies Haines spotted Thursday along the stream, 17 of them were born in the wild.

At the beginning of the campaign last year, the team installed in the stream bed some aquatic plant species that the damselflies are known to like. But as the weather grew drier over the summer, wild pigs seeking out the moisture trampled through the stream and ruined the work.

Haines said the team now plans to partially fence off the stream, to protect the habitat from the pigs, and create some artificial pools in an effort to increase the stream’s carrying capacity and stability.

The effort, he said, will also look for other suitable release sites and target additional native damselflies in trouble for reintroduction.