The male Schaus swallowtail butterfly is an endangered species. (Dr. Thomas C. Emmel/University of Florida)

Butterflies are the essence of cool in the insect world, a favorite muse for poets and songwriters, who hold them up as symbols of love, beauty, transformation and good fortune.

But providing good fortune apparently goes only one way. As humans rip apart woods and meadows for housing developments and insecticide-soaked lawns, butterflies across the country are disappearing.

The U.S. Fish and Wildlife Service recently announced that two brown, mothlike butterfly subspecies are probably 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 the Fish and Wildlife Service. “We’re looking at this as sort of a wake-up call that we need to be watching butterflies more closely.”

At least one species of butterfly has vanished from the United States, along with the two subspecies in South Florida. 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 individual 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, if you don’t have a place to lay eggs, 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.

Pesticide use has 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 K. Robbins, a research entomologist at the Smithsonian Institution’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 animals 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 the Fish and Wildlife Service waited at least a decade to announce the extinction of the skippers.

The last confirmed extinction of a butterfly species was of 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 around us,” Robbins 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 in their decline.

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

“Every single day the number of butterflies in the United States decreases, because every day a meadow is developed into a lot,” said Jeffrey Glassberg, president of the 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 larva.

Mark Salvato, a Fish and Wildlife Service 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 the plants and the butterfly larva. “It was kind of like a perfect storm,” he said.