(CNN) -- In a region saturated with spectacular aquamarine waters and bright coral reefs, the colorful Schaus swallowtail butterfly once was a familiar sight as it flitted over Biscayne National Park in South Florida.
But the insect's numbers have declined over the past decade. With only five recent sightings, three confirmed, at the island park, federal wildlife officials are trying to save the species from extinction.
The U.S. Fish and Wildlife Service late last week issued an emergency authorization to collect up to four Schaus swallowtail females within the park and collect and raise their eggs.
"This is a very low number of individuals compared to what should be in the field," said Jaret Daniels, an entomology researcher with the University of Florida.
Biologists and state and federal officials, in a conference call Wednesday, said there was no one factor responsible for the butterfly's decline.
Habitat destruction, drought, hurricanes and pesticide use outside Biscayne National Park are likely contributing, they said.
Also, the Schaus swallowtail's breeding habits aren't helping.
"It has one generation a year, which is unusual for a subtropical butterfly," said Daniels.
The Schaus swallowtail, contained to a relatively small area in southeast Florida, in 1976 was listed under the Endangered Species Act as threatened. It reached the endangered status eight years later.
During the 2011 survey, there were 41 sightings, mostly on Elliott Key, the park's largest island. Six of the 41 were found on north Key Largo.
Finding, or for that matter catching, four females won't be easy. Of the five sightings since May, only one was a female.
"This is needle in a haystack stuff," said Elane Nuehring, president of the Miami Blue chapter of the North American Butterfly Association.
Once collected -- very carefully -- females will be temporarily confined in a mesh cage in their natural habitat, according to the U.S. Fish and Wildlife Service and National Park Service.
The hope is that they will lay eggs on host plants inside the cage. Females will be confined for up to four days and then released. The eggs will be placed in small vials and transported to the University of Florida in Gainesville for rearing.
The butterflies will emerge bearing black-brown wings with yellow markings and a broad rusty patch beneath the hind wing. Adults have a life span of one month.
Captive breeding also was done in the 1980s and 1990s, boosting the Schaus numbers for a time.
"There was great hope at that time the reintroductions would bolster the population," said Nuehring. "As time went on, the reintroduced populations began to dwindle yet again. This time, it has been harder to figure out why."
"Captivation is normally a last-ditch effort," said Ricardo Zambrano, a biologist with the Florida Fish and Wildlife Conservation Commission.
Surveys of the species, assisted by the North American Butterfly Association and other volunteers, will continue through the end of June.
Normally hardy, the Schaus swallowtail is accustomed to living in a harsh environment that is accompanied by the occasional hurricane.
"Extended drought has played an extensive role in this butterfly's decline," Daniels said.
Biscayne National Park, south of Miami, supports intact native habitat, critical for the Schaus swallowtail's survival, and does not use pesticides to control mosquitoes.
The butterfly's food sources include cheese shrub, guava nectar and the torchwood tree, according to the Butterfly Conservation Initiative.
In a separate habitat restoration project in the area, officials are replacing invasive plant species with ones more typically found in hammock forests, said Dana Hartley, a U.S. Fish and Wildlife Service biologist.
Experts say pollinators such as butterflies are at risk throughout the United States.
Elsa Alvear, chief of natural resources at Biscayne National Park, said the reduced use of pesticides at home and in gardens, coupled with the introduction of native plants, will help their numbers.
Schaus swallowtails are big, charismatic butterflies, Nuehring told CNN.
The butterfly group is concerned about other imperiled butterflies in South Florida and elsewhere.
"Some people might argue extinction is a natural thing, that we lose species all the time," Nuehring said. "(But) you lose genetic diversity whenever something disappears."