No trace left of three types of butterflies native to south Florida ORLANDO, Florida (Reuters) - After six years of searching, an entomologist has concluded that three varieties of butterflies native to south Florida have become extinct, nearly doubling the number of North American butterflies known to be gone. These are unique butterflies to Florida. This is our biological treasure. Each unique species that we lose, we won't ever get that back again," Marc Minno, who conducted the survey for the U.S. Fish and Wildlife Service and the Florida Keys Mosquito Control District, told Reuters on Monday. The disappearance of butterflies should serve as a warning about the degradation of south Florida's environment, he said. It's indicating there are major problems, environmental harm to Florida. And this is an indication that quality for people is also degrading and people should be worried about that," Minno said. Before Minno's survey, only four varieties of North American butterflies, all from California, were presumed to be extinct, and the last one added to the list was 55 years ago. Besides the three varieties which Minno concluded are extinct, two more native butterflies no longer exist in Florida but are living in the Caribbean, and two more are heading toward extinction, he said. What is happening to the Florida butterflies remains an unanswered question. The Schaus' Swallowtail, found only in the upper Florida Keys, became in 1976 one of the first insects ever given legal protection under the federal Endangered Species Act. Minno said only six of the swallowtails were sighted in 2012. Scientists began noticing a general decline in the butterfly populations in the 1980s, and Minno, like many scientists, assumed the spraying of pesticides to kill mosquitoes might be at fault. But his survey suggested otherwise. In urban areas, such as Key West which has little natural habitat remaining and is routinely sprayed, Minno said, "There are so many butterflies flying you can hardly keep track of them all. There are just swarms of butterflies sometimes. You just wonder what the heck is going on. It's just the opposite of what you would think. By contrast, Minno said he found few butterflies in vast conservations lands without mosquito control, such as the million-acre Everglades National Park and Biscayne National Park. One of his theories is that mosquito spraying might bolster butterfly populations by killing off native and non-native parasitic wasps which feast on butterfly larvae and caterpillars. Another theory is that invasive predatory ants, such as the Mexican twig ant and fire ants, which were introduced to the area in the 1970s and are unrestrained by pesticides in conservation areas, might be overwhelming butterfly populations there. Minno said the three butterflies that were found only in southern Florida and are now extinct are the Florida Zestos Skipper, the Rockland Meske's Skipper, and the Keys Zarucco Skipper. In addition, the Bahamian Swallowtails and the Nickerbean Blues are gone from Florida but alive in the Caribbean. Minno also expects the Shaus' Swallowtail and the Miami Blue, both of which continue to decline despite formal recovery plans, to become extinct soon. Of 120 varieties of butterflies documented in the Keys, Minno said 18 have become imperiled since the 1970s. Minno said no state, federal or private agency has funded research to find out what is causing the decline. Editing by Tom Brown and Phil Berlowitz