WASHINGTON –

Butterflies are a favorite muse for poets and songwriters who hold them up as symbols of love, beauty, transformation and good fortune.

But the good fortune apparently only goes one way. As humans rip apart woods and meadows for housing developments with their chemicals-soaked lawns, these insects are disappearing across America.

The U.S. Fish and Wildlife Service recently declared two brown, mothlike subspecies to likely be extinct in south Florida, which some entomologists say is ground zero for the number of butterfly species on the verge of annihilation.

The rockland grass skipper went missing in 1999, and the Zestos skipper hasn't been seen since 2004. Several other species, such as the ebony-and-ivory-colored Schaus swallowtail, are listed as endangered, and many others are threatened, including the silvery Bartram's hairstreak.

"We look at it as a signal that we've got a serious problem with butterflies and other insects and pollinators here in Florida," said Larry Williams, a supervisor for the ecological services program at Fish and Wildlife.

At least one species of butterfly has gone from the United States, along with the two subspecies. Seventeen species and subspecies are listed as endangered nationwide, and two are listed as threatened.

Habitat loss is a major problem, as are bug sprays, especially those used by municipalities and homeowners to control mosquitoes. "We know that it's becoming increasingly popular for homeowners to use misting systems to spray low levels of pesticides. As those become more abundant, we have to evaluate if those are contributing to the decline," Williams said.

To Laurie Davies Adams, executive director of Pollinator Partnership, a group dedicated to the conservation of insects such as bees, moths and butterflies, the explanation for the butterfly decline is simple.

"If you don't have a place to nest, or to lay eggs, and if you don't have a place to get the floral resources you need, because they're absent because of drought or early bloom, you're in trouble," Adams said.

The same issues plaguing butterflies are also causing populations of frogs, salamanders and toads to plummet, along with bees and other insects. A recent U.S. Geological Survey study estimated that seven species of amphibians will drop by 50 percent if the current rate of decline, fueled by pesticide use and loss of habitat, continues.

Pesticides have also led to a collapse of other pollinators — wasps, beetles and especially honeybees. At least 25,000 bumblebees were recently found dead at an Oregon parking lot, ironically during National Pollinator Week, which started June 18.

Why should anyone care about losing butterflies, asked Robert Robbins, a research entomologist at the Smithsonian's Museum of Natural History. Although the insect looks fragile, like most bugs it clings to existence more ferociously than mammals. If butterflies are going extinct, "it's a strong indicator that we're messing up the environment around us," Robbins said.

Numerous mammals such as Carolina parakeets and passenger pigeons have vanished, but butterflies have been known to disappear in one place and show up in another, which is why Fish and Wildlife waited at least a decade to announce the extinction of the skippers.

The last confirmed extinction of a butterfly species was the blueberry-colored Xerces blue, which disappeared from San Francisco sand dunes that were commercially developed, Robbins said.

Like all flora and fauna, humans stand to gain a lot from the presence of a butterfly species — a possible medical breakthrough from study and biomedical research, for example, Robbins said. But he sees a bigger picture. When an entire line dies off, "it's a report card on the health of the environment," he said. "We depend on fresh air and food that isn't full of chemicals. I think that's a more important aspect than maybe we would've discovered a gene that would've cured some disease. It's our general survival."

Eighty percent of food crops are pollinated by insects such as bees, moths and butterflies, according to scientists. Nearly a third of the nation's honeybees have disappeared, and scientists theorize that pesticide use is a contributing factor.

It's not that butterflies will be wiped off the face of the Earth anytime soon. There are 650 to 750 species in the U.S. alone, and slightly fewer than 20,000 worldwide. Peru has a quarter of those, and species explode in tropical areas such as the Caribbean. But their decline in the U.S. is rapid and troubling.

"Every single day the number of butterflies in the U.S. decreases, because every day a meadow is developed into a lot," said Jeffrey Glassberg, president of North American Butterfly Association.

"And then I would say second is pesticide use," he said. It doesn't have to be this way, he said. "It would be really easy for people to make a significant difference in the environment just by the way they planted their suburban yards. Many butterflies would be increased by planting your yard with the right native plants."

Butterflies live a few days or a few weeks, depending on the species. Females lay a few hundred eggs in a lifetime, Williams said. Generally, they lay about a half dozen at one time.

A larva emerges and slowly feeds on plant leaves. Even those are threatened by invasive species introduced by humans, such as the green iguana in Florida, which eats the plants along with the larvae.

Mark Salvato, a Fish and Wildlife biologist, hacked his way through pine scrub at Bahia Honda State Park in the Florida Keys and discovered that first-hand with the endangered Miami blue butterfly.

"A very large iguana population was eating the Miami blue host plant," Salvato said. After a two-year cold snap ending in 2010, the plants died back, and when they returned, iguanas pounced, devouring both plants and the butterfly larvae. "It was kind of like a perfect storm," he said.